Bulletin


STATE OF ILLINOIS

DEPARTMENT OF REGISTRATION AND EDUCATION

DIVISION OF THE

.
NATURAL HISTORY SURVEY

STEPHEN A. FORBES. Chief

Vol. XV. BULLETIN Article V.

Changes in the Small Bottom Fauna of Peoria

Lake, 1920 to 1922

BY

ROBERT E. RICHARDSON

PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS

URBANA, ILLINOS

August, 1925



ERRATA
Page 57, statistical headings: for Year 1920 read Year I'JIO; for Year W09 read

Year HUG; in the ratio heading, for 1909 read 1920, and for 1920 read 1910.

The entries in the Year columns should change places.

Page 85, line 13 from bottom, for 87 read 86.

Page 88, line 20, delete red.

Page 115, line 6, over the column of figures read Acres.

Page 136, line 5, for /J.T read 131.

Page 145, First table, 4th column, for S5.9~ read 33.40; last column, for .052

read .0418.

Second table, second column, for .2158 read .2004; 5th column, for

.1131 read .0977; last column, for .0926 read .0772.

Last table, second column, for .714 read .663 and for total read $4,710;

5th column, for .374 read .323 and for total read $2,201; the last column,

for .307 read .256 and for total read $1,700.

Page 146: First table, second column, for 8.02 read 7.45 and for total read

52.92; third column, for 3.45 read 2.88 and for total read 19.10; 4th column

for 19.28 read 17.90 and for total read 127.18; last column, for 8.29 read

6.92 and for total read 46.35.

Second table, for 43.02 read 38.66.

Last table, for 8.0 read 6.7.

Page 382. line 10 from bottom, for Plat ytlieinis read Plathcmis.

Page 385, in list, the specific names of No.'s 33, 35, and 40 should end in ns

instead of a.

Pages 445 (line 4), 448 (line 4), 449 (line 23), 454 (line 8 from bottom), read

Belostomklac for Belostomatidae.

Page 457, line 21, for cornutus read cornuta.



STATE OF ILLINOIS

DEPARTMENT OP REGISTRATION AND EDUCATION

A. M. Shelton, Director

BOARD OF

NATURAL RESOURCES AND CONSERVATION

A. M. Sheltox, CTiairvian

Wlliam Teelease, Biology John W. Alvokd. Engineering

John M. Coulter, Forestry Kendeic C. Babcock. Representing the

Edson S. Bastin, Geology President of the University of lUi-

WiLLiAM A. NoYES. Chcviistry nois

THE NATURAL HISTORY SURVEY DIVISION

Stephen A. Forbes, Chief

SciiNEpr & Barnbs, Printers
Springfield. III.

1925

34183—900



CONTENTS

PAOE

Introduction 327

Destruction of the old bottom fauna . . . ; 327

Terminology with reference to degree of pollution and tolerance 333

Hydrographical subdivision 334

Summary 336

Upper Peoria Lake and the Illinois River, Chillicothe to Spring Bay
(Mile 146.5—153.2 below Lake Michigan):

Hydrography 338

Dissolved oxygen 339

Small bottom animals 341

Middle Peoria Lake, Mossville to Al Fresco Park (Mile 154.9—159.3

below Lake Michigan):

Hydrography 353

Dissolved oxygen '. 354

Small bottom animals 356

Lower Peoria Lake and Illinois River, Peoria Narrows to Peoria and
Pekin Union Railway Bridge (Mile 161.0—166.4 below Lake
Michigan)

:

Hydrography 365

Dissolved oxygen 366

Small bottom animals 367

Comparison of the recent small invertebrate bottom and weed fauna of

Peoria Lake with that of 1913-1915 377

Commoner small bottom animals that have disappeared since 1915 379

Almost complete extinction of an abundant and varied mussel fauna
since 1913-1915 384

Bibliography 387

Comparison of 1922 and 1920 species lists, detail 389



Article \'.

—

Cliaiigcs in the Small Bottom Fauna of Peoria Lake,

ip^o to iij32. By Rcibekt E. Richardson.

Introduction

Early in July ]9v!2 the cooperative program of chemical and bio-

logical investigations of the middle Illinois River and Peoria Lake

begun in the summer of 1920 by the State Natural History Survey and

the State Water Survey was again taken up after an interval of two

years. The summer's work included, as one item among several others,

between the date of opening and the middle of September, quantitative

bottom dredgings at seventy-one stations in the channel and wide

waters of Peoria Lake and contiguous river between Chillicothe and

the Peoria and Pekin L'nion Railway Bridge opposite the lower part

of the city of Peoria. The dredging stations were distributed over

approximately the area covered by the thirty-five stations worked in

Peoria Lake in the summer of 1920, and covered a linear distance of

19.9 miles. Collections were made and handled as in 1920. Assist-

ance was furnished by Dr. C. P. Alexander in determining the larval

Chironomidae (midges), by Mr. F. C. Baker and by Dr. \^ Stei-ki on

snails of the family Sphaeriidac, and by Prof. Frank Smith and Dr.

J. P. Moore on the worms and leeches. The nitrogen- data on which

the 1921 curve of per cent free ammonia is based have been furnished

in advance of publication by the U. S. Public Health Service.

Destruction of the Old Botto.m F.\un.\

In a paper* published in December, 1921, on the changes in the

bottom and shore fauna of the middle Illinois River, it was shown that

between the period 1913-1915 and the summer of 1920, there had been

an almost complete extermination of the older normal bottom popula-

tion over a stretch of around 90 miles of river, including Peoria Lake,

extending from Chillicothe to Beardsiown. The same jieriod also saw

• Bui. ni. Nat. Hist. Surv., Vol. XIV. Art. 4. pp. 33-75.



328

the point of practically complete oxygen exhaustion, a foot below the

surface, in midsummer, move 83 miles down stream, from Morris,

C3.5 miles below Chicago, to Chillicothe, UG.ri miles below ; and saw

the surface dissolved oxygen at the same time of year fall from around

1 p. p. m. to as low as 1 p. p. m. at Havana, 20T miles below Chicago.

During the same five or six years, also, the zone of high free ammonia,

with the ratio (per cent) on the base of the total nitrogen between 40

and 60 per cent, moved down the river more than 50 miles, or from

Spring Valley, 108.6 miles below Chicago, to Peoria Narrows, 160.9

miles below ; while the upper limits of the zone of well clarified effluent,

with free ammonia around or under 10 per cent of the total nitrogen,

receded from Beardstown to Kampsville, a distance of about 5? miles,

or to within about 30 miles of the mouth of the 327 mile continuous

waterway to Grafton. See charts following.

Between 1914 and 1918 the total weight of animals slaughtered

at the Chicago stockyards (Tables, pp. 331 and 332) had increased at

a rate more than eight times as fast as the estimated normal rate of

increase of human population; and there had been large increase in

the rates of operation of the Corn Products Refining plants both at

Argo and Pekin ; while the average dilution employed in the Chicago

Sanitary Canal was changed in an amount relatively small.

The years 1911 to 1911 inclusive had been rather quiescent years

for the packing industry, the total weight of animals slaughtered drop-

ping off gradually during that time from about 3,3S3 million pounds

in 1911 to 3,040 million pounds in 1914. From the 1914 low figure

the weight of slaughterings climbed rapidly, with only a slight reces-

sion during 1917, to a peak of 4,870 million pounds in 1918. represent-

ing an increase of fully GO per cent over the 1914 yearly rate (^Tablc.

p. 332) ; and about oO per cent over the average rate of 3.258 million

pounds for the four years 1911-1914.

The increase in the Packingtown wastes entering the sanitary

canal in the four years 1914 to 1918 amounted in population equivalent

on the basis of the Sanitary District's own figures* to more than

523,000 persons, or almost treble the estimated actual increase in human

population during the period ; or to more than the total 1920 popula-

tion of the city of Buffalo, New York. During peak weeks of 19 16,

• Packingtown Report II. 1921, pp. 8. 14. 231, etc.











339

191 T, and 1918 the weekly rale of killings ran for weeks at a time at

more than double the average weekly rate of 1914; and in November
and December, 1918, particularly, at rates representing increases of 110

to 145 per cent over the average weekly rate five years earlier. These

weekly peaks were in the late fall or early winter, when it is presumed

that a large portion of the wastes would settle to the bottom, not far

away from their source, ready to be washed out, still to a considerable

extent undecomposed, with the first heavy rains of spring.

Heavy mortality among the snails was noted at points all the way

from Spring Valley to Havana during and following summer floods

in 1917. In August of that year dead snails acres in extent were seen

floating down the Illinois past Peoria and Havana ; and in places

were from one to two feet deep along the water-front at Peoria.

In late summer 1918, while in the field with chemists of the State

Water Survey, it was noted that all snails except one species of Mus-

culium and one Campeloma of imusual hardiness seemed already to

have been killed both at Lacon and Chillicothe. During the five weeks

July 22 to August 31 that year we got our first records of surface

dissolved oxygen under one part per million south of Spring Valley

—

finding them then extending as far sputh as Lacon*.

After 1918, up to the end of 1921, there was a long-sustained re-

cession in the packing industry, which carried the slaughtering figures

off more than a billion and a third pounds from the 1918 peak, or to

wifhin 443 million pounds of the 1914 rate (only 14.5 per cent above

the 1914 figure).

Between 1921 and 1928 the slaughtering rate moved up 400 mil-

lion pounds to a year total for 1922 of 3,975 million, and this was ac-

complished without seeming to exert any further seriously unfavorable

influence on chemical or biological conditions ; except as it was possibly

reflected in increase in numbers of the sludge or nuid worms (Tubi-

ficidae).

The present paper compares the condition of the bottom fauna of

Peoria Lake as found in July-September, 1922, with that of the sum-

mer of 1920, which was probably very close to its point of low condi-

tion following the mortality of 1917-1918, just referred to; with the

result, in general, of indicating an essentially slight though measurable

improvement in the two years.

•Third Annual Report. State Dlv. Waterways, 1919-19:'li. pp. 28-32.



330

Since 1932 there has continued a gradual rise in the Packingtown

slaughterings, which brought them at the end of 1923 to a year total

of 4,461 million pounds, or to a point again only 8.4 per cent under

the 1918 peak of 4,870 billion pounds.

ToL-VL Weight of Amsials Slaughtered axd

Population Equivalent 1911-1924



331

Weight of Animals Slaughtered—Cattle, She3:p, a.nd Hogs onxt

weekly rate, pounds



332

Changes in Chicago PoPtx.A.TioN (Est.) and

Packingtown Equivalent, 1914 to 1918



333

Terminology with Reference to Degree of

Pollution and Tolerance

The terms used in the present paper to describe the varying de-

grees of tolerance exhibited by the small bottom animals do not differ

essentially from those used by Forbes and Richardson, 1913: i. e.,

septic, pollutional, contaminate, and clean-ivater, in order of decreas-

ing pollution. For the purpose of greater flexibility and at the same

time better suitability of application to the animals themselves, I have

substituted the word tolerant, with qualifying adjectives, for the word

contaminate as used in the 1913 paper. After the comparatively few

cases of species in the present bottom fauna with authentic previous

records of pollutional or unusually tolerant habit*, the tests of tolerance

used have been (1) survival under conditions of much lower than

normal oxygen supply; (2) association with other authentic pollutional

or unusually tolerant species; or (3) survival in areas where species

of known cleaner preferences have wholly succumbed. It can not be

too strongly urged that at the best we do not find in the actual field

habitats the hard and fast lines perhaps too easily suggested by the

use of these and other group terms by authors. The great flexibility

called for in classifications of the kind is particularly well illustrated

in the recent species lists from the bottom muds of Peoria Lake, which

may be said to have been neither septic at the worst nor clean at the

best, either in 1920 or 1922; by the occurrence there side by side in

both years of tubificid worms and midge larvae characteristic of the

septic zones of the upper Illinois, and of a number of species of sphae-

riid snails thought of usually heretofore as of clean-water habit, though

now shown to have more than the ordinary amount of tolerance.

The approximate position of the various subdivisions of Peoria

Lake in the zonal system above recognized may be outlined as follows,

basing conclusions on the chemical, plankton, and bottom-fauna data

of 1920 and 1922.

/. Pollutional Zone:—Chillicothc to lozver End

of Upper Peoria Lake. Distance 7.5 miles

The dissolved oxygen in midsummer both in 1920 and 1922 ranged

here normally between 0.5 and under 3 p. p. m. Though below the

septic zone, in the most proper sense, this is still the zone of vast num-

• Includes Tubifcx tubifcx ; CMronomua pluvwaus, and a very few others.



334

bers of Tubificidae, including Tubifex and several species of Limno-

drilus ; as well as of Chironomus plimiosiis. Practically the only snails

surviving here recently are those that are more than ordinarily tolerant

—the list including several species of Sphaeriidae, but only one mem-
ber of the family Viviparidae (Cainpeloma subsoUdum) . On the

plankton side this is the zone of blue-green algae, these organisms, both

filamentous and non-filamentous types, .giving a blackish blue color

to the plankton samples, easily visible to the unaided eye immediately

after treatment with alcohol-formalin preservative, in the case of col-

lections made either in July, August, or September, and as far south

as Spring Bay Narrows or even the upper end of the middle lake.

Rotifer tardus was common in the plankton in the summer of 1920,

while shelled rotifers were rare.

2. Sub-poUulioiial or Contaminate Zone; or Zone of Tolerant

Bottom Animals:—Head or Center of Middle Peoria

Lake to foot of Loiver Peoria Lake

Distance about 12 miles

The dissolved oxygen ranged usually from around 2.5 to more

than 5 p. p. ni. through the summer season, both 1930 and 1922. The

blackish blue color given the upper lake plankton by the blue-greens

begins to disappear rapidly at or just below Mossville ; the blue-green

organisms thereafter giving way to great increase in chlamydomonads

and other chlorophyll-bearing forms. Shelled types of rotifers of the

family Brachionidae increase rapidly down the middle lake and Rotifer

tardus tapers out almost altogether at Peoria Narrows. In the bottom

fauna, sphaeriid snails increase in variety in the middle lake, but the

Viviparidae and Amnicolidae remain absent, both there and in the

lower lake. In the lower lake, areas or zones of heavy local pollution

and of unusually fast current cause mixed conditions ; and there are

otherwise in this portion of the river more or less insensible gradations

between conditions nearly clean, contaminate, and poUutional.

1 IvDUOGR.APHICAL SUBDIVISION

The bottom collections made in the summer of 1922 were all made

under substantially average low water conditions. Although we went

several times within between 50 and 100 feet from shore with the

dredge, few depths under five feet were found even at that distance

;



335

while traces of vegetation worth mentioning were found at only two

stations in all three lakes all stimnier. The collections of 1922 are thus

practically altogether open-lake dredgings, from areas where the bottom

animals are subject to the full influence of low oxygen when it occurs,

and where they receive a minimum of aid from the reacrating or

freshening eiTects of shore vegetation and spring water. Noting the

very wide extent to which the largely deaerated waters of the river

spread out in the upper lake wide-waters opposite Rome—where the

bottom dissolved oxygen was under 1 p. p. m. for fully a half mile to

the eastward of the mid-channel line on August 9, 1922—it has seemed

best to emphasize distance from mid-channel rather than depth in the

zonal subdivision of the wide waters. Thus in all cross-sections in

1932 in the lake proper we had first a mid-channel stop, in an imagi-

nary channel some 700 feet wide, the approximate width of the luain

channel at ChiUicothe ; next a first wide-water zone embracing several

collections in which the first haul was usually taken 400 to 600 feet

to either side of the mid-channel line; and last a second wide-water

zone extending from 1800 to 4500 feet eastward or westward of the

mid-channel line, depending upon the width of the lake in the area

crossed.

A table of distances down stream between stations at which cross-

sections were made, follows.



336

Table op Mile Numbers and Distances, Peoria Lake, 1922



337

2. The extension of range of the surviving Sphaeriidae between

1920 and 1923 went hand in hand with large expansion (following the

lull due to business depression of 1921) in the Packingtown slaughter-

ings at Chicago, and with tremendous increase in numbers of tubificid

worms in the nuids of tlie upper lake and the river at Chillicolhe ; and

suggests perhaps a progressive immunization of the already tolerant

sphaeriid snails to conditions which a few years earlier might have

gone harder with them.

3. Both in the upper and the middle lake .in 1933 improvement in

the condition of the muds is indicated by increase in variety of the

species lists (1) as we proceed down stream; and (2) as we proceed

outward from mid-channel stations into the wide waters.

4. In the lower lake there are various evidences of mixed con-

ditions on the bottom, partly due, in the wide waters, to wind-blown

local pollution ; and so far as suitable situations for a few cleaner-

preference forms are provided, apparently due to the much greater

current that prevails in the lower lake channel, or in the narrows (in

our results included as lake stations) immediately above or below it.

5. Species that have definitely disappeared from Peoria Lake

since 1913-1915 include all but three or four kinds out of a total of

more than forty kinds of fresh-water mussels; all of the snails of the

family Aninicolidae ; all but one species of the formerly important and

especially conspicuous snail family Viviparidae ; and a varied weed

fauna.

C. P'rom the rather restricted list of small bottom invertebrates

that seem to have been exterminated in Peoria Lake since 1913-1915,

compared with the decidedly larger lists from the vicinity of Havana*,

it is suggested that upper and middle Peoria Lake may have been

subjected to a measurable amount of injury from up-river pdllution

prior to 1915.

• Sec Article VI of this volume, on 1"J23 fauna.



338

Upper Peoria Lake and the Illinois River, Chillicothe to

Spring Bay. (Mile 146.5—153.2 below Lake
Michigan)

Hydrography

The three cross-sections in the upper lake district in 1022 began

with one in the river proper at Chillicothe. which is only a half mile

above the present low-water head of the upper lake, 6.7 miles above

its approximate foot at Spring Bay, and 14.5 miles above the head of

the lower lake at Peoria Narrows. The two cross-sections through

the lake proper included one at Rome, 2.8 miles below Chillicothe,

where the extreme width at recent summer low water has been in the

neighborhood of 4,800 feet; and one on a line a mile and a half above

Spring Bay, 5.2 miles below Chillicothe, where low water widths have

recently been somewhat more than G.OOO feet. ^lid-channel depths

at Chillicothe in August 1922 were around 22 feet, but were only 13

or 14 feet opposite Rome and Spring Bay, at the first of which places

considerable filling has evidently occurred since 1901. The soiuidings

made in the east wide-waters opposite Rome were not over 6.5 feet

in the first 1,500 feet; and did not exceed 5 feet in the next 2.000. A
mile and a half above Spring Bay depths in the open lake were nnich

greater, nine- fo more than ten-foot soundings continuing for 3.500

feet beyond the mid-channel line on the east or widest side. The

bottom in the river at Chillicothe was deep mud ; and throughout the

upper lake was uniformly soft black nuid at the stations visited, except

on the far west side above Spring Bay, where harder mixed nuid and

gravel bottom reaches out a hundred feet or more from the bank at

low water.

Though the odors of the bottom sediments in the upper lake

showed striking differences between 1915 and 1920, as described in a

previous paper, it was not always an easy matter to make out reciUy

definite differences between the summers of 1920 and 1922. While

some average improvement evidently occurred in the two years, it

wa^ clear also that there was still abundant room for more. Sum-
marizing the records from this portion of the lake for the summer
of 1922, it is fountl that we noted abundant bubbling at all stations;

distinctly foul odors at seven stations out of the total of twenty-three

;

mildly bad odors at nine out of the twenty-three stations ; and had no



330

record or records of uncertain value at seven stations. This exhibit

compares with bad odors at all stations in the summer of 1!)20, but is

qualified in value by the feature that worse odors were noted in the

summer of 1922 well to the east and west of the main channel than

within it. both opposite Rome and just above Spring Bay ; and rather

milder ones in the river channel at Chillicothe than at the worst sta-

tions in the wide-water cross-sections three to five miles farther south.

The possibility that the very unusual flood of January-April 1922

flushed out the channel at the same time that it brought in a new load

of putrescible sediment to the wide waters suggests itself as a plau-

sible explanation of some of these changes, as also of the fact that the

spongy gas-filled mud noted in the summer of 1920 at several upper

lake stations in or near the steamboat channel did not appear in any of

our 1922 dredge hauls.

Toward the west bank below Rome some spreading of Potamoge-

ton occurred between 1920 and 1922 ; and in September 1922 mats of

Lemnaceae were found here, and also in the brushy southwest corner

of the upper lake opposite Spring Bay. The total area supplied with

vegetation is, however, insignificant compared with that of the low-

water period between 1910 and 1915, on gages little if any lower. No
living vegetation at all was encountered at any of tiic stations actually

dredged in the summer of 1922.

Dissolved Oxygen

The dissolved oxygen one foot from the bottom in mid-channel

at Chillicothe fell as low as 0.3 p. p. m. in July 1922, and to 0.2 p. p. m.

in August. The bottom oxygen during the same period in mid-channel

opposite Rome dropped to 0.2 p. p. m. on July 3, 1922 ; rose to 2.0

p. p. m. on July 27; fell to 0.5 on August 9; and rose again to 1.G on

August 29. On August 9, when the bottom oxygen in the channel at

Rome was 0.5 p. p. m., bottom figures under one part per million were

recorded at six wide-water stations east of the steamboat channel in

the Rome cross-section, averaging more than 600 feet apart and ex-

tending altogether more than 3600 feet eastward of the mid-channel

station.

At points between a mile and a half above Spring Bay and the

foot of the upper lake at Spring Bay Narrows, which is 7.7 miles be-

low Chillicothe. the bottom dissolved oxygen in July and .lugiist 1922



340

ranged between 1.4 and 3.9 parts per million. The bottom figure on

July 88, 1922, at Spring Bay Narrows (1.4 p. p. m.) was lower than

the figure at Rome the day before; but both on July 3, 1922 (when

it was 3.3 at Spring Bay Narrows), and on August 29, 1922 (when

it was 3.9), a relatively large improvement had taken place in the

approximate five-miles distance between Rome and the foot of the lake.

The variation in the gage at Peoria during the period July 3 to August

29 was a little less than two feet. The lowest bottom dissolved oxygen

figures at Chillicothe were recorded on July 3, August 9, and August

29, on gages 11.3, 10.4, and 9.8 feet corresponding; and the highest

on a gage of 10.7 feet on July 27. The lowest bottom figures at Rome
occurred on July 3 at a gage of 11.3 feet Peoria, and on Augfust 9 at

gage 10.4; while the high figures (1.6 to 2.0 p. p. m.) came on July 27

and August 29 on gages 10.7 and 9.8 feet.

Bottom oxygen figures slightly lower than any of these were re-

corded at Chillicothe and Rome and in the vicinity of Spring Bay in

the summer of 1920. A table comparing the channel figures from the

upper lake and Chillicothe for 1922 and 1920 follows.

Bottom Dissolved O.xyoen, Mio-Ciianxei-, Upper Peoria Lake, 1920-1922

midsummer figures, parts per mii.liox

Peo. gage



341

Small Bottom Animals

Nineteen species of small bottom invertebrates were recorded from

twenty-three dredging stations between Chillicothe and a mile and a

half above Spring Bay, near the lower end of upper Peoria Lake, in

the summer of 1922 (Table, p. 342). This increased number compare;

with eleven or twelve kinds taken at eight stations in very nearly the

same area in the corresponding months of 1920. That the increase

may to some extent be due to the greater number of stations visited,

particularly in the wide waters, in 1922, has not been allowed to escape

our notice. IMore probable explanations, however, include the increase

in the worm list (+2) due to a more thorough study of that group

in 1922, and the evident increase, mostly in the wide waters, of the

less tolerant snails (+5), that seem to have escaped total destruction

between 1915 and 1920, but that had not had time by 1920 to extend

again over their old range sufficiently to make the chance good of

getting them in collections. It will be noted, also, in ensuing pages,

that other equally important changes were apparent at the end of the

two year interval that could have no possible connection with an in-

crease in the number of stations.

Both in 1922 and 1920 the majority of the species taken in the

upper lake, whether in channel or wide waters, belonged to the more

distinctly pollutional or tolerant groups of small bottom animals; that

is, small annelid worms (Tubificidae), leeches, midge larvae, and toler-

ant snails. The more sensitive varieties of the old snail, insect, crus-

tacean, and other small bottom population of 191.j and before were

in 1922 as in 1920 wholly absent from all hauls taken in the upper

lake more than 50 feet from shore. There was, however, to be set

down fairly definitely on the side of improvement during the two years

following 1920 the noticeable increase in the number of kinds and

abundance of the tolerant snails, already mentioned ; and, more quali-

fiedly, because they may have merely been washed out by the violent

flood of the spring of 1922, the decrease in both numbers and kinds of

more pollutional midge larvae. Suggesting caution, on the other hand,

in accepting at face value these apparent evidences of improvement,

was the remarkable increase in abundance at all stations in the upper

lake in 1922 of the small oligochaete worms, which were present in

numbers exceeding any that we have before recorded from anywhere

in the Illinois River.



343

As will be seen in the tables that follow, there was noticeable a

sharp difference between the rates of increase in the species lists in

mid-channel and in the open lake from 1920 to 1922. In fact, substan-

tially no. favorable change in number seems to have occurred in the two

years in the channel, where decrease in kinds of midges was balanced

by increase in worms, leeches, and tolerant snails ; and where, in 1922,

the number of all species taken decreased instead of increasing as we
proceeded down the lake from Chillicothe. In the wide waters, on

the other hand, there was an increase in the list of species in the two

years from 11+ to 18+ ; and the increase was almost all due to the

multiplication in variety of the less tolerant kinds of snails and midges,

(see Table below). Further evidence of improvement in the extra-

channel zones is seen as we go down stream (see Table on following

page) ; as also in the near to more than doubling of the species lists in

size, both in the Rome and the Spring Bay cross-section, as we move
outward from the channel into the wide waters (Table on p. 344).

Summary of Bottom Species Lists, Uppee Peoria Lake, Summer 1922

1. comparison with 1920. number of kixds takex



343

Summary of Bottom Si-ecies Lists, Upper Peoria Lake, Summer 1922

2. t'hanoes down stream. number of kinds taken



344

Summary of Bottom Spkcies Lists. Upper Peoeia Lake. Summer 1922

3. changes from mid-channel outward into wide waters

rrUMBER OF KINDS TAKEN



345

related family of free living worms known as Naididae was rejiresented

by small numbers of one or more undetermined species.

The species of the genera Tubifex and Limnodrilus live in tubes

or burrows in the soft top ooze of stream bottoms, from which they

protrude the posterior end, waving it constantly when imdisturbfd, as

an accessory act in respiration. When very abundant these worms
literally carpet the bottom with a living naji of reddish brown or deeii

red. This fact is the more easily visualized by those who have not

seen them when it is known that they occurred in luiinbers as high as

fiO.OOO per square yard in upper Peoria Lake in the summer of 1922.

Such numbers amount to nearly 'J.jO rows of 250 each in such a space,

and call for a separation between individuals amounting to less than

fifteen-hundredths of an inch in each direction.

The several times recorded occurrence of Tubifex tubifex in un-

usually septic situations in recent years by European writers, as about

the edges of septic tanks and very near the sources of the pollution

in sewage-fouled streams, seems to have led to the entire group being

referred to rather indiscriminately by local authors la ely as "slime

worms" or "sludge worms," with little or no reference at all to the

possible varying preferences or the identity of individual species. This

has been no doubt largely a result of the difficult and time-consuming

technique necessary in the determination of species in this group, and

the extreme rarity of specialists competent to render an opinion upon

them. Some of them occur quite frequently, however, in ordinary

clean bottom in our inland lakes and streams; and extensive carpets

of them have been observed near the edges of deep reservoirs thought

clean enough to be a part of the source of a city's water supply. Even

Tubifex tubifex has recently been reported by Muttkowski (1918)

from the bottom muds of Lake Mcndota; and was found, as repre-

sented by the American form as here understood, to be commonly

present in the comparatively clean nuids of thf Illinois River at and

near Havana in the early days of operations at the Illinois Biological

Station.

Of the Tubificidae taken in upper Peoria L:ike in 1!)22 far the

most abundant one was not T. tubifex as might have been ex])ectcd on

the basis of recent .American and European records, but Lintiiodrilus

Iwffmeistcri. This worm occurred at twenty-one out of twenty-three

of the collecting stations in the ui)per lake, including all cross-sections,

and like T. tubifex and the undescribed species of Limnodrilus was



346

most abundant in the two upper cross-sections, opposite Chillicothe

and Rome, at the latter of which the dissolved oxygen one foot above

bottom was under one part per million at stations embracing over a

mile of lake-width early in August. The species was also taken, how-

ever, at a large proportion of the stations in the upper part of the

middle lake and at a few in the lower.

The undescribed species of Limnodriliis had a distribution in the

summer of 1922 very much like that of L. hoffiiieisteri, be'ing taken at

nineteen out of the twenty-three upper lake stations, embracing three

cross-sections ; and was also taken in scattered hauls both In the middle

and the lower lake. Tuhifcx tubifex, on the other hand, was taken in

or just above the upper lake in 1922 only in the Chillicothe and Rome
cross-sections, where it occurred at only six out of twelve stations

;

was not recorded at all from the eleven stations in the Spring Bay

cross-section ; and was recorded only once each from the middle and

lower lakes.

The distinct tendency toward confinement of Tubifex tuhifcx, as

here understood, to the Chillicothe and Roman cross-sections may be

accepted as further confirmation of the value of that species as an indi-

cator of bad bottom ; though it is believed that the facts of outside

distribution before mentioned suggest that great caution be used before

basing conclusions as to the cleanness of muds upon mere occurrence,

either of this or other species.

When the totals of all Tubificidae are tabulated, it is suggested

that numbers may be quite as important as specific identity when we

are seeking an index of the condition of the bottom muds in the small

annelids. Averaging 22,400 at Chillicothe, and averaging 29,000 and

ranging as high as 69,000 opposite Rome in early August, 1922, the

total of all worms dropped to only 2,100 per square yard in the next

2.4 miles (cross-section 1.5 miles above Spring Bay) ; and to a figure

of only 420 per square yard in the first cross-section in the middle

lake, another 4.5 miles south. The sharp decline in the 2.4 miles be-

tween Rome and the next cross-section southward corresponded to a

rise of less than two parts per million in the bottom dissolved oxygen

on the round of August 9, 1922, and was proportionately more eni-

frtiatic than the oxygen figures in suggesting the rapidity of improve-

ment in the water and the muds after they spread out into the upper

lake wide-waters just above Rome.



347

Collections
averaged



348

The reasons for the iiiucli greater abundance of these worms in

the summer of 1922 than in the summer of 1920, when the average

oxygen supply was somewhat less at the lowest than in 1922 at upper

lake stations, are not clear unless we assume that the increase followed,

as it might quite naturally, the bringing in with the very unusual flood

of the winter and spring of 1922 of a new load of rich sediments, along

with a richer bottom bacterial flora, than were present in the summer
of 1920, following a more quiescent spring season. In fact, these

worms do not seem to be bound to their habitat so much by a quali-

tative as by a quantitative food relation, deriving their sustenance

as they do, without apparent selection, from the bacteria and other

living and dead organic matter in the soft bottom-sediments, which

they first swallow oi masse. So far as a low oxygen supply is con-

cerned, they seem merely able to tolerate it by virtue of their ability to

store haemoglobin and to effect a mechanical aeration of their imme-

diate surroundings, rather than to be in any true sense partial or obli-

gate to it.

LEECHES

Two species of leeches were taken in the upper lake in the summer
of 1922 : the first, Erpobdclla f<unctata (Leidy), in the channel opposite

Chillicothe; the second, Hclobdclla nephcloid'\i (Graf), in the wide

waters 3,600 feet eastward of mid-channel in the cross-section a mile

and a half above Spring Bay. The first species mentioned was taken

also in 1922 in the river at the P. P. U. Railway Bridge opposite the

lower part of the city of Peoria whei'e the pretty well aerated waters

of the lower lake are being mixed with the discharge from the main

sewers. ErpobdcUa punctata was noted by Baker (1922) as common
at stations in the Big Vermilion River in 1918-1920 where gas bubbling

was continuous in warm weather and where the mussels were dead

;

and by Weston and Turner (191T) as common at the upper and worst

polluted stations in the Covveeset below Brockton, Massachusetts.

Muttkovvski (1918), on the other hand, reported ErpobdcUa f'linctata

to be common along clean gravelly shores of Lake Mendota.

Hclobdclla ncphcloldca, in addition to its occurrence in the upper

lake above Spring Bay at stations where distinctly bad X)dors were re-

corded, was also taken in the wide waters of the middle lake opposite

Mossville ; in the steamboat channel and the wide waters of the lower

lake opposite Fulton Street, Peoria; and. in company with ErpobdcUa



349

punctata, below the outlet of the lower lake at the P. P. U. Railway

Bridge. We have found no definite outside records of habitats of this

species. The conclusion is evidently to be drawn, with respect both to

this and the other species named, that they are of rather indifferent

value as an index" of the condition of muds in the Illinois River.

MIDGE I,.\KVAE

Larvae of midges occurred in oin- 1933 dredge-hauls from upper

Peoria Lake at only eight out of the total of twenty-three stations, and

failed altogether to appear at any of the channel stations. The total

number of identified kinds was the same as in the summer of 1930,

but three of the more pollutional species of that year were not taken

at all in 1923, and the single 1932 species known to be unusually toler-

ant (C. plumosus Linn., var.) occurred only at three extra-channel

upper lake stations, one each in the Chillicothe, Rome, and Spring Bay
cross-sections. Undetermined species of Chironomus, Procladius, and

Tanypus were taken at a few open lake stations well eastward of the

channel opposite Rome and Spring Bay; and a few specimens of Tanv-

pus monilis Linn., in the past reported only from cleaner situations,

were taken toward the west side opposite Rome, in a haul in which

tubificid worms exceeded 7,000 per square yard and unusually foul

odors "were noted.

In the summer of 1930 all channel hauls contained midge larvae,

though the recognized more tolerant kinds then as in 1933 came from

the stations outside the channel. In the middle lake and in the lower

in 1922 larval Chironomidae occurred at a nuich larger projjortion of

all stations than in the upjjer lake, although no important increase in

numbers was noted at the stations southward.

With the exception of C. plumosus or its varieties, and of two

other pollutional species (C. dccorus Johannscn and Tanypus dyar't

Coquillett) taken rather frequently in the summer of 1930, neither in

1933 or 1930 did numbers of chironomid larvae attain importance in

Peoria Lake (Table, p. 317). The first-named species does, however,

seem to bear an unusually distinct relation to pollution ; as has been

noted since some years ago in studies of its sister forms in Europe,

where variation in the length of its ventral blood-gills has been ob-

served to coincide more or less definitely with diflferences in the oxygen

sui^ply. The recent Illinois River and Peoria Lake specimens which

we have referred to this species do not seem to differ very materially



350

except in that respect from the abundant larva formerly referred to

C. fcntans in our work of ten years or so ago at and above Havana—

-

a form which seems to have wholly disappeared from this section of

the Illinois River since some time before 1920. The practical confine-

ment of the more poUutional kinds of midge larvae recently to the lake

zones outside the channel, while to an extent perhaps a result of habitat

preference unconnected with pollution, places them conveniently in

those areas where the bottom receives the largest fresh supplies of rich

sediment as the gage recedes after floods.

UNUSUALLY TOLER.^NT SX.MLS

One of the most surprising facts that came out of the study of

the bottom dredgings from upper Peoria Lake was the enormous multi-

plication at Chillicothe and in the lake opposite Rome between 1920

and 1933 of the little sphaeriid snail, MuscuUum traiisz'crsiiiit Linsley.

Nuinbers of this small bivalve, familiar to local hunters and fishermen

under the name of "duck shell", reached a hundred thousand per square

yard in parts of the upper portion of the upper lake in the summer of

1923. Average numbers for all stations in cross-sections passed 51,000

at Chillicothe and 39,000 opposite Rome, these figures representing

equivalents of weight valuations between 19,000 and 25,000 pounds

per acre over limited areas, on the supposition' that all the yourfg and

half grown lived to become adult. The distribution of the largest

hauls of this little snail agreed closely with the location of the largest

catches of mud worms, and also an equally abrupt average decline in

the Musculium figures corresponded to the drop in worm figures al-

ready mentioned as having taken place in the two miles between the

Rome cross-section and the next one south. This decline was followed

by further decrease or showed little recovery in the areas sampled in

the middle and lower lakes. (Table, p. 347.)

The ability of this snail to withstand low oxygen is well supported

by previous evidence from the Illinois River, where it occurred in

small numbers near the banks as far north as Marseilles in the sum-

mers of 1911 and 1912. Its recent extremely rapid nuiltiplication in

the worst instead of the best portion of its old range in Peoria Lake.

amounting to from 50 to more than 2,000 times numbers as of the

summer of 1920, may be supposed, however, to reflect quite probably

some other factor than those involved in the original habitat preferences

of the species. Perhaps it is true that an important consideration has



351

been that this snail has recently met almost no hindrance to multipli-

cation from its greatest predatory enemy, the carp, in this poorly

aerated section of Peoria Lake. The supposition that its recent dis-

tribution and abundance has been in substance inverse to that of the

coarse bottom-feeding fishes is borne out by such information as we
have concerning the location of the most profitable seine hauls recently

above Peoria Narrows. It may also be the case that there has re-

cently been some increase in an already relatively strong innnunity in

this species to the ill efiects of low oxygen.

LESS TOLERANT SNAILS

It was in the group of less tolerant snails that the greatest increase

in variety of the small bottom fauna of the upper lake occurred in the

two years following 1920. The species included under this designa-

tion are all evidently less tolerant than MhschUuiii transvcrsnm, as

shown both by their greater rarity in upper Peoria Lake in 1922, and

by the fact that none of them occurred quite so far north in the Illi-

nois River in 1912 as that very tolerant species. Though less tolerant

than that unusually hardy form, they are all evidently considerably

more so than several other snail species (particularly Vhipara contec-

toidcs Binney, V. suhpnrpurca Say, Lioplax subcarinatus Say, and

Anmicola emarginata Kiister), all of which were common in Peoria

Lake up to 1915 but have not since appeared in collections from either

the upper, middle, or lower lake. Though no representative of this

group could be called abundant at any upper lake station in 1922, we

took then, in all, five species, all but one belonging to the Sphaeriidae,

compared with a single S])ecies in 1920. The channel collections con-

tributed two species, MusciiUkiii tnntcatum Linsley and Pisidiitni coiii-

prcssiim Prime, against none at all in 1920; and the collections from

the open lake five kinds, M. truticatum, P. compressum, P. paupcrcn-

liiw var. crystalcnse Sterki, a species of Pisidium near P. complanalitm

Sterki, and Caiiipcloimi subsolidiiui Anthony, as against the last species

alone in the summer of 1920.

Of these five snails, only one, the large viviparid, C. subsolidttin,

has been previously known through published records, so far as we

know, to be much more than ordinarily resistant to pollution or low

oxygen. This snail was taken by us in the Illinois River in 1912 as

far north as Starved Rock, or farther north than any other snail excejjt

Mitscniiiiiii transvcrstiiit ; and was recently reported by Miss Jewell



352

(1922) from the acid waters of the Big Muddy. The distribution of

Campeloma siibsoUdum in upper Peoria Lake in 1922, was confined

to two stations in the far east wide-waters a mile and a half above

Spring Bay. Bad odors and abundant bubbling were noted at both of

these stations, and the bottom dissolved oxygen was under three parts

per million in July, and considerably lower in August.

While MnscuUum trtmcatum did not appear at all in 1920 collec-

tions from any part of Peoria Lake, in August 1922 we found it at

seven out of the nine stations in the Rome cross-section, including the

channel, and at one station in the upper portion of the middle lake.

Numbers in the Rome cross-section ran as high as TOO per square

yard, and the species was associated with Tubificidae at stations where

they exceeded forty thousand. This species was found in the Illinois

River channel in 1919 as far north as De Pue and Spring Valley, and

seems to possess not far from as high a degree of tolerance as its

more prolific coingener, M. transversiim. It seems, in fact, to differ

from it mainly at the present time in Peoria Lake as it did in the past

in the cleaner waters of the Illinois, in a lesser aptitude for multiply-

ing and occupying the capacity of its range.

Of the three species of Pisidium taken in the upper lake in 1922,

P. compressum had much the widest distribution, occurring at six out

of the total of 23 stations, compared with no records at all in 1920.

It was present at three stations in the Rome cross-section, including

the mid-channel station, and was associated there with Tubificidae and

other annelid worms whose combined numbers exceeded 45.000. per

square yard. This little shell also occurred in the upper lake in 1922

at three stations toward the west end of the Spring Bay cross-section,

and extended southward into the middle lake and the upper jwrtion of

the lower. In 1912 it was taken in the channel of the Illinois at Spring

Valley, De Pue, Henr\-, and Chillicothe.

Pisidium paupcrculuni, var. crystalciisc Sterki occurred in the

upper lake in 1922 at only two stations, both west of the main channel

in the cross-section a mile and half above Spring Bay. At one of

these two hauls unvisually bad odors were noted and Tubificidae and

other small annelids passed 5,000 per square yard. ' The species was

not taken in the Illinois River above Henry in the summer of 1912,

and is apparently to be graded as somewhat less tolerant than P. com-

pressuni.



353

A third species of Pisidium, close to P. complanatiiin Sterki, was
taken twice in the summer of 1922 in the far east wide-waters of the

upper lake, once in the Rome and once in the Spring Bay cross-r.ection.

Tubificidae exceeded 6,000 per square yard at one of these stations

and especially bad odors were recorded at both.

It may be mentioned here that Miss Emmeline Moore (informa-

tion by correspondence) found Pisidium compressum and also an un-

named species near P. abditnin Haldcman in waters of the Skaneateles

outlet, New York, recently, under conditions that suggested a high

degree of tolerance. It is also of interest in the present connection

to recall that Juday (1908) took a species of this genus (P. idahoensc

Roper) in the deeper waters of the glacial lakes of Wisconsin, at

depths where for more than two months in the year there •\vas nearly

if not complete oxygen exhaustion. These specimens were found to

be quiescent under those conditions, but to revive upon being placed

in well-aerated water.

Belonging to a group of snails and other botlo.ni species still less

tolerant than the Pisidia, is the little Valvata tricarinala Say, which we
took in small numbers in August 1932 about a hundred feet from the

west bank opposite Spring Bay. Here there was somewhat solider

bottom than farther out in the lake, though no vegetation ; and no

especially bad odor was recorded. As this species is more frequently

than not a shore form and more than ordinarily partial to vegetation,

the question of the amount of tolerance possessed by it does not affect

any conclusions already or later drawn as to the condition of the bottom

nnids of the great portion of upper Peoria Lake.

Middle Peoria Lake, Mossville to Al Fresco Park
(Mile 154.9—159.3 below Lake Michigan)

Hydrography

The three bottom fauna cross-sections through the middle lake in

the summer of 1922 began at Mossville, 3.2 miles below the last sec-

tion in the upper lake, and were approximately two miles apart in all

cases. The one at Mossville was 8.4 miles below Chillicothe, the one

at the foot of Horshor Island 10.9 miles below, and the one opposite

Al Fresco Park 12.8 miles below the first cross-section taken in 1922.

The width of Peoria Lake at Mossville in August 1922 was around

4,500 feet ; but had rapidly expanded to al)out 7,000 opposite the foot



354

of Horshor Island ; and declined again to about 3,500 at Al Fresco

Park. Mid-channel depths in the first two cross-sections were not

over 13 feet, but were 18 feet opposite Al Fresco Park, where the Icike

is beginning to taper to the lower narrows and the current is notice-

ably stronger than farther northward. Extra-channel depths in the

middle lake cross-sections were nearly all over seven feet, and depths

of nine to ten feet were met in all three throughout a total width sweep

of 2,500 to 3,000 feet. Soft mud bottom was found everywhere ex-

cept in the last hundred feet next the west bank, where there was some

sand or gravel.

A more readily recognizable change for the better since 1 920 could

be perceived in the bottom sediments of the middle lake in the summer
of 1922 than was the case in the upper. Although bubbling was abun-

dant at nearly all stations, and mild bad odors at a majority of them,

no very foul odors such as were encountered in or near the channel

as far south as Al Fresco Park in 1920 were noticed anywhere in the

middle lake in the summer of 1922. Improvement between Mossville

and Al Fresco Park, a distance of about four and a half miles, was

clearly evidenced by the entire absence of foul odors and the fewness

of bubbles at a number of the wide-waters stations opposite the latter

place.

Replacement of vegetation does not seem to have progressed so

far in the two years since 1920 in the middle as in the upper lake, a

circumstance possibly having some connection with the fact that the

middle lake is regularly seined. Sparse patches of Potamogeton and

Vallisneria were visible near the west bank in late August and early

September 1922 in the lower half of the lake, but the great weed-beds

that formerly covered hundreds of acres in the upper half of the lake

were as absent from the landscape as they were in 1920.

Dissolved Oxygen

There was a plentiful supply of dissolved oxygen over the greater

part of the middle lake in July 1922, when on gages between 11.3

and 10.7 feet more than five parts per million were -found a foot from

the bottom a mile below Mossville, and nearly or more than six parts

per million opposite Al Fresco Park in mid-channel samples. But

before the end of the first two weeks of .\ugust, on a gage down to

10,3 feet, the mid-chnnncl tigure a mile below ^lossville had dropped



355

to 2.2 p. p. m., and was only 3.4 p. p. m. a mile and a half above the

foot of the lake. Similar mid-channel figures (2.8 p. p. ni. one foot

from bottom) were obtained a mile below Mossville late in August

(gage 9.8 feet) ; and on September 13, after a slight rise, when the

low figure for 1922, 1.7 p. p. m., was recorded. At Al Fresco Park

on the last two dates mid-channel bottom oxygen was 5.3 and 4 p. p. ni.

In the wide waters a mile below Mossville the bottom oxygen rose

rapidly toward the west bank in late July 1922, topping 10.2 p. p. m.,

or about a part and a half above saturation, about a hundred feet from

shore on July 28. But in the far east wide-waters on the same date

the figures obtained a foot from the bottom ranged between 3.1 and

3.4 p. p. m., or a part to more than that lower than the channel figures.

However, at this time, in the wide waters as in the channel, bottom

oxygen figures rose rapidly as we proceeded down the lake, ranging

between four and six parts per million opposite the foot of Horshor

Island and six to more than seven opposite Al Fresco Park. On
August 9, 1922, bottom figures were under 1 p. p. m. in the open lake

at three stations in the cross-section a mile below Mossville, and were

as high as 3 p. p. m. only at distances more than 3,000 feet east or

2,000 west of mid-channel (it will be noted that the lake is some 2,000

feet wider at low water here than directly opposite Mossville). (Jn

the same date open lake figures opposite Al Fresco Park were under

4 p. p. m. as far as 1,300 feet east of the mid-channel line, but had

risen to 6.7 p. p. m. within a total of 2,000 feet.

In August 1920 appreciably lower bottom dissolved oxygen figures

than any of those obtained in the summer of 1920 were recorded from

the middle lake, both in its upper portion in the vicinity of Mossville

and toward the lower end opposite Al Fresco Park. Then, as in 1922,

there was sometimes quite rapid improvement from the channel out-

ward into the wide waters, particularly in the lower portion. But in

the second week of August 1920, figures under 1 p. p. m. were found

more than 2,500 feet to the east of the mid-channel line at Al Fresco

Park. Neither in 1920 nor 1922 did these extreme low figures have a

very extended duration in the open lake, but were likely to be succeeded

within a week or two, coincidently with a sudden increase in the green

microplankton, by figures four to five parts per million higher. Even

bottom dissolved oxygen figures above saturation were recorded once

in 1920 from a middle lake wide-water station, late in August, though



356

this was in the lower part of the lake, and not above the middle as in

the latter part of July 1922.

Bottom Dissolved Oxygen, Mid-chaxnkl, Middle Peobia Lake. 1920-1922

Midsummer Figures, Parts per Million

Peoria



357

Compared with 1!)20, there was substantially a doubling in var-

iety of the 1922 lists, whether in channel, wide waters, or all zones

combined (Table 2, p. 358). The increases over 1!)20 were principally

due to multiplication of kinds of the less tolerant snails, which rose in

the two years from one to ten species ; and to the less tolerant kinds

of larval midges, which increased from two kinds to five. Both the

snails and the less tolerant midges showed the greatest gain in the

wide waters, at the same time that the more pollutional kinds of midges

fell off in representation in the extra-channel areas as compared with

1920.

The changes in the species lists of the middle lake from its upper

to its low-er end in 1922 were irregular in the channel, the Al Fresco

Park stations showing scarcely better than those opposite Mossville,

four and a half iiiiles above (Table on p. 359). The largest variety of

channel species was found in the intermediate cross-section, opposite

the foot of Horshor Island, and about half way between the head and

the foot of the lake. In the wide waters there was a more regular

showing of improvement southward from Mossville, both the Horshor

Island and the Al Fresco cross-sections yielding nearly or quite twice

as many of the less tolerant snails and from three to four times as

man}' of the less tolerant midges as were taken opposite the Mossville

station.

In all three of the middle lake cross-sections of 1922 there was

marked increase in variety of species as we proceeded outward into

the wide waters from the steamboat channel (Table on p. 360). This

improvement was mainly due in all three cross-sections to the increase

in number of kinds of less tolerant snails ; which rose in the Moss-

ville section from none in the channel to three kinds in the wide waters

;

in the Horshor Island section from three kinds in the channel to six

kinds in the wide waters ; and in the Al Fresco Park section from one

kind in the channel to five kinds at the extra-channel stations.



358

Summary of Bottom Species Lists, Middle Peoeia Lake, Summer of 1922

1. comparison with upper lake. number of kinds taken



359

Summary of Bottom Species Lists, Middle Peokia Lake, Simmeu of 1922

3. changes dowx stueam. number of kinds taken

o =3S

*



360

Summary of Bottom Species Lists. Middle Peoria Lake, Summer 1922

4. changes from muvchannel outward into wide waters

numbers of kinds taken



361

WORMS

Except for the irregular continuation of the decline in numbers

already noticed in the upper lake, and their failure to appear at all in

the collections opposite Al Fresco Park, the lubificid worms presented

little of interest in the middle lake in the summer of 1933. Substan-

tially the same list of species was found as in the upper lake, though

in all cases in much smaller average numbers and with more scattered

distribution. The various species of Limnodrilus, rather than Tuhifex

tubifcx, led as in the upper lake in frequency ; while the local form of

Tubifcx tubifex was found at only a single station in the channel oppo-

site the foot of Horshor Island.

The absence of small annelids from the Al Fresco Park hauls is

not to be taken as conclusive evidence that they were not there al-

though noticeably improved conditions on the bottom were visible also

in other respects. It is more probable that if we had increased the

fraction of the Petersen dredge sample sieved for them at least small

numbers of some of the species would have been found.

LEECHES

Leeches were represented in the 1923 middle lake hauls by two

species, the same number as in the upper lake. One of them, Heloh-

della ncphcloidca (Graf), occurred in the wide waters of the Mossville

cross-section, and was also recorded in 1923 from the wide waters of

the upper lake above Spring Bay. The second, HelobdcUa stacpialis

(Linnaeus), although it occurred in the middle lake in 1933 only in

the lower or Al Fresco Park cross-section, was one of the two com-

monest leeches at the more heavily polluted stations of the Coweeset

just below Brockton, Massachusetts, in 1914 (Weston and Turner

191?). ErpobdcUa punctata (Leidy), which was taken in the channel

at Chillicothe in 1923 and was the other common leech at the upper

Coweeset hauls in 1914, was not found in middle Peoria Lake collec-

tions in the season of 1922.

MIDGE L.\RVAE

While a total of six species of immature midges were recorded

from the middle lake in the summer of 1922, compared with five in

1920, the more distinctly tolerant or pollutional kinds were reduced

in 1922 in the middle as in the upper lake from three to only one. The



3G2

one, a variety of Chirouomus plutnosus Linnaeus or a species very

closely allied to it, occurred at fourteen of the thirty stations covered

in the middle lake in \'.)'2'2. It was, however, absent in all collections

in the upper or Mossville cross-section, and reached its highest aver-

age numbers in the cross-section opposite the foot of Horshor Island,

or through almost the exact center of the lake.

Chironomids of more uncertain status were represented in the

middle lake hauls of the summer of 1!)22 b)' not less than five species.

Of these, Chirouomus digitatus jMalloch has not before to our knowl-

edge been recorded from any but ordinarily clean bottom. The others

included a species very near C. matiiriis Johannsen, which was taken

in foul muds in the lower lake both in 1922 and 1920 ; and an uncertain

number of unidentified kinds of Chironomus, Tanypus, and Procladius.

UNUSUALLY TOLER.ANT SN'.MLS

While the snails were easily led in abundance in the middle lake

as in the upper in the summer of 1922 by the vmusually tolerant Miiscu-

liutn transvcrsum Say, the figures for that species were small compared

with the numbers reached by it the same season in the upper lake. The

largest all-station average of a single cross-section amounted only to

a little over 2,500 per square yard, or about a fifteenth of the average

of the nine 1922 stations in the best upper lake cross-section (opposite

Rome) ; and the smallest to only one sixtieth of the nine-station aver-

age of the same cross-section. Though so small compared with upper

lake figures, those of the middle lake represented valuation equivalents

between 200 and nearly 500 pounds per acre and made up the largest

single item by weight of the whole 1922 middle lake bottom fauna.

LESS toli:r.\nt sn.mls

Ten other kinds of snails, all presumed to be of lesser tolerance

than MuscitHum transvcrsum but more tolerant than several species

of the old fauna that have not appeared in any part of the open waters

of Peoria Lake since before 1920, and all but one belonging to the

Sphaeriidae, were taken in the middle lake in the summer of 1922.

Numbers were small in all cases, and all recorded occurrences were

at stations well away from the channel and toward the east or west

margins of the lake, or, if wiilely distributed, in its lower portion.

This number of species is just double that of the less tolerant groi^>

of snails listed from the ujiper lake in 1922, and compares with a



3C3

single snail species besides M. transvcrsum from the middle lake in

1920. Five of these species were the same as the five already listed

from the upper lake on a preceding page. This group, distinguished

from the other five by the fact of occurrence above the middle lake

in 1923, included one sphaeriid of the genus Musculium, one viviparid,

and three species of the sphaeriid genus Pisidium, sometimes called

pea-clams in the literature. The five new entrants in the 1923 li.sts,

embracing snails whose farthest northward occurrence in 1922 was

the middle lake, included three additional species of Pisidium not taken

in the upper lake in 1922 or in any part of either the upper, middle,

or lower lakes in 1920, and two species of Sphaeriuni, also not taken

in the upper lake in the summer of 1922, but one of them recorded

from the lower lake in 1930.

The distinction between these two groups of the less tolerant snails

and their relation, in the matter of tolerance to pollution, to the other

recent snail groups and to the Viviparidae and Amnicolidae apparently

exterminated between 1915 and 1920 is shown in the table that follows.



364

° S «

S '-3

C8 Sa> -^

o t2

O CO

CD o !;i

snsoqoi3qns
snaX3o}Biuos

BSOUin

Giooiurav

sin^niJBoqns
xBidoiT

Bajndjndqns
•BJBdiAlA

sapioiDejuoo
B-IBdlAJA

o ^
c a

a

<:

o
Ed

o

O a
o 43

0!

t-
_t. S-

g- a.

9 5

*-* -^ r5
u; o "

;3
a

J H

c ~
t3

go

suaosaAii
sisBqoiuoj)

HSIAiai UBA
uin}BAaia Bjaoojnaxd

asaaqsB3jfni 'Jba

'uinunBUjs 's

ranauiniBjs
ranijaBqds

sapads
uinipisij

sapads
ninipisitj

ran[no.iadnEd
lUHipiSIJ

mnpjiosqns
BiuopdatBO

UIIUBUBldlUOO jBau
•ds lunipisij

asnaiB^sX.io jba
'raninojadiiBd j
uinssajdiuoo

mnipisid

ninjBonnJi

rans.iaAsuBJ}
mniinosriK

6 c

*-* O <ll ?*
p. 03 O
3 t; i; j=

.5? S 3 s ^ _

c _ .2 rt

\
-

1



365

Lower Peoria Lake and Illinois River, Peoria Narrows
to Peoria and Pekin Union Railway Bridge

(Mile 161.0—166.4 below Lake Michigan)

HVDK0GKA^HY

In or adjacent to lower Peoria Lake in the summer of ]y"22 bottom

dredgings were made at eighteen stations in four cross-sections. Col-

lections began at the foot of Peoria Narrows, which is just above the

head of the lower lake wide-waters and is not far from a quarter of

a mile wide at recent low water, and ended at the P. P. U. Railway

Bridge across the Illinois River about a mile and a half below the

foot, which lies slightly below the center of the city of Peoria. The

two intermediate cross-sections through the lake proper were opposite

Workhouse Point, a little less than two miles below the Narrows ; and

opposite the foot of Fulton Street, a mile and a half below the first

open lake cross-section and less than a mile above the lake's foot. The
full width of the lake was somewhat more than a mile at the Point

and considerably less than a mile opposite Fulton Street, though a]i-

preciably wider in between, during the summer months of 1!)22.

Though a good deal smaller, as measured either by length or

width, than the upper or the middle lake, being only about three aiifl

a half miles long as compared with nearly six for the middle lake and

more than six for the upper, the lower lake with its immediately con-

tiguous areas, as here regarded, presents a visibly greater variety of

habitats than either of the others, and differs from them also in several

other main features. Its entire lower half is narrowed to an efYectual

width of much less than a mile by a long submerged but formerly

wooded island on the east side, whose outside edge is only about three

quarters of a mile from tlie Peoria water-front opposite. The effect

of this is that throughout the central and lower portion of the lower

lake, where our main cross-sections were made both in ]!)22 and 1!I20.

the great body of moving water passes through a relatively narrow

and deep prism, with depths between twelve and fourteen feet pre-

vailing over a total width of nearly half a mile, and with, as a conse-

quence, a greater average current everywhere in the open portion than

in corresponding sections of the upper or middle lake.

The west littoral of the lower lake receives the discharge from

most of the main sewers and industrial drains of a city of nearly

100,000 people, but although this is true, during the summer season



366

the prevailing direction of the winds and the current together seem to

keep this soiHng material largely confined between the channel and

the bank as far as the foot of the lake, where the first extensive mix-

ing of lake water and local sewage appears ordinarily to take place.

The general orientation of both the channel and the adjacent wide-

waters is such, however, that in the fall of the year and occasionally

during the summer season, north or slightly north of west winds may
cause much more mixing of the sewage with the lake water eastward.

Soft mud bottom was met at all stations in the lower lake proper.

Harder mud and shell bottom was found in midstream at the Narrows,

and nearly clean sand at the P. P. U. Bridge, where the current is

four to five times that in the channel opposite Workhouse Point and

six to seven times midstream current riieasured near the middle of

the middle lake in the summer of 1930.

Since the first cross-section in the lake proper was above most of

the main sewers, and we confined our collecting below that place to

the channel and the open lake eastward of it, no especial foul odors

were recorded at any of the lower lake stations in the 1922 summer
season. Bubbling was observed in abundance at most stations op-

posite Workhouse Point, as also at the farthest eastward stations op-

posite Fulton Street, but in the middle of the main channel and at

most open lake stations opposite Fulton Street neither bubbles nor

unusually bad odors were noted.

Little restoration of the killed-out vegetation in the southeastern

part of the lower lake had occurred in the two years since 1920, the

thin Potamogeton patcli on the east side facing Liberty Street looking

about as it did in the summer of 1920. Traces of Vallisneria were

brought up by the dredge at the station nearest the we.^t shore off

Workhouse Point, but no vegetation was encountered in any other

hauls.

Dissolved O.xvgen

Both in the summer of 1922 and of 1920 the supply of dissolved

oxygen a foot from the bottom in mid-channel at the foot of Peoria

Narrows ranged between 50 and 75 per cent of saturation, numerous

samples taken between the middle of July and the middle of Sep-

tember 1920 averaging 5.1 to 6.4 parts per million, and eight samples

taken in September 1922 averaging 4.8, with a range from 3.6 to 6.2

p. p, m.' Soon after the middle of July 1920 almost as high or higher



3Gr

figures than at the Narrows continued in mid-channel to and below

the foot of the lake. But in the first week of August 1920 the bottom

oxygen dropped sharply below the Narrows from a high figure for

the season of 6.4 p. p. m. to only 3.4 a mile below, and to 2.0 p. p. m.

opposite Green Street, which is a mile above the foot of the lake. On
the same dates a rapid rise in bottom oxygen figures from the channel

eastward into the wide waters was noted a mile below the Narrows

;

but opposite Green Street samples showed between three and two

parts per million for two fifths of a mile eastward into the open lake.

Bottom Dissolved O.xygen, Mio-C'HA.\Ntx, Loweu Peouia Lake, 1920-1922

Midsummer Figures, Parts per Million—Averages



368

number from ten kinds to only four kinds of the less tolerant snails,

at the same time with the first appearance below Chillicothe of seven

miscellaneous small botloni animals of presumably lesser tolerance

than any of the groups taken either in 1922 or 1920 in the middle or

the upper lake.

The comparison of 1922 collections from the lower lake with

those of 1920 (Table on p. 3?0) showed less dicerence than app>eared

either in the upper or middle lake, and suggests that this section of

the lake, with its greater average current, and its long histor)- of local

pollution, has at the present time a small bottom population somewhat

better adjusted to the prevailing conditions than has been the case

recently in the portions of the lake above Peoria Narrows.

As we would expect from the heavy local pollution adjacent to

the channel on the east side, there was a greater increase in variety

in the species lists from the channel outward into the wide waters

(from 2 kinds to 12 kinds in the Workhouse Point cross-section; and

from 8 kinds to 17 kinds in the Fulton Street section) than either in

the middle or the upper lake (Table on p. 372). This was despite the

fact that the corrective action of the more rapid current in and also

well outside of the channel here permits the existence of several cur-

rent-loving forms that have not been found since- 1015 above the lower

lake ; and that wind- or wave-carried local pollution has apparently

reduced the number of kinds of the less tolerant Sphaeriidae in the

wide waters.

The changes in the lower lake species lists down stream (Table

on p. 371) were irregular and of no special significance.



369

OQ (M

Ed «
»• Sm S
« M
O if

^ so <

(1. r-

o



370

Summary of Bottom Species Lists, Lower Peokia Lajce, Summer of 1922

2. comparison with 1920. number of kinds taken



371

Summary of Bottom Species Lists, Lower Peoria Lake, Summer 1922

, 3. changes down stream, number of kinds taken



372

Summary op Bottom Spbx:ibs Lists, Lower Peoria Lake, Simmer 1922

4. changes from mid-chan.nel outward ivto wide waters.

NUMBe'R OF KINDS TAKEN



373

and upper lake figures and with the lower lake figures for 1920, which

for unknown reasons averaged even less than those of 1928, is shown

in the table on page 3-l~ preceding.

LEECH F.S

Four species of leeches were taken in the lower lake in the sum-

mer of 1922, which was more than were found in either the middle

or upper lake in 1922 or in the lower in 1920. These four species in-

cluded Erpobdella punctata and Helohdclla stagnalis, both of which

have been recently listed from outside of Illinois in polluted bottom;

Helobdclla nephcloidca. which was taken in the upper lake above

Spring Bay in 1922 where odors were bad and bubbles were abundant;

and Dina parva, of which we have no local or outside records from

foul bottom. Erpobdella punctata was found only in the mixture of

local sewage and lake water at the P. P. U. Bridge, below the foot of

the lake, that and the occurrence in mid-channel at Chillicothe being

the only records obtained anywhere in the summer of 1922. With a

single exception, occurrences of iiie other three species were limited

to the Fulton Street cross-section, where leeches were especially com-

mon in the suminer of 1922 both in channel and extra-channel collec-

tions.

MIDGE LARVAE

Though average abundance of midge larvae did not go as high in

the lower lake as in the upper and middle lakes in the summer of

1922, both the total number of species identified and the number known

to be more than usually tolerant was greater. The three pollutional

forms included the common one from the upper and middle lakes,

Chironomns pUimosus, var. as well as also typical C. plumosus, which

was taken once opposite Fulton Street ; and C. nmtiirus Johannsen,

which was taken at two hauls in the cross-section opposite Workhouse

Point. In addition there were upwards of five or six kinds of Chiro-

nomidae of more or less doubtful position, two of them apparently less

tolerant than the three above mentioned. These two were Cliirono-

mtis digitatus Malloch, which was also taken in the middle cross-sec-

tion in the middle lake in 1922, and which occurred in clean iriuds in

Lake Mendota, studied by Muttkowski in 1918; and Tanypiis uioiiilis

Linnaeus, found once in the Fulton Street cross-section, well to the

eastward, and except for its occurrence not far from mid-channel

opposite Rome in August 1922, not known to us to favor bad bottom.



374

UNUSUALLY TOLERANT SXAILS

Musculium transversum, the leader of the water-breathing snails

in enduring low oxygen and other effects of pollution in upper Peoria

Lake, continued in the lower lake to still lower levels the decline begun

between Rome and Spring Bay in the summer of 1922 and showed no

increase worth mentioning over 1920 abundance (Table, p. 347).

The lower lake has recently had ordinarily a sufficient supply of oxy-

gen at levels well above the bottom for the coarser commercial fishes,

and is subject to little or no seining as a consequence of the almost

entire absence of good landing places. Perhaps the little-restricted

fish foraging may account in part for the small numbers recently found

not only of this species but also of others, including mud worms and

midge larvae, in the lower lake. A second circumstance that may
have bearing on the recent scarcity of this snail in lower Peoria Lake

is that in the period between 1913 and 1915, when bottom conditions

were more nearly normal in this part of the Illinois River, the upper

lake was, as in 1922, its principal stronghold. In those years the

lower lake snail fauna was largely made up of species of Viviparidae

and Pleuroceridae, though 71/. traiisz'crsiiin was also taken in some

hauls in moderate or small numbers.

LESS TOLERANT SNAILS

The less tolerant snails from lower lake hauls in the summer of

1928 were of only four kinds, as against ten kinds from the middle

lake the same season, but no more than three from the lower lake in

the summer of 1920. Three of these, Pmdinm coiiiprissuiii, P. pau-

perculum, var. crystalcnse, and Campcloma subsoliduni were present

both in upper and middle lake collections in 1932, while the fourth,

Spliacriiim staiuinciini. had its farthest northward 1922 occurrence in

the middle lake. All four of them were found in the Peoria Narrows

hauls, and three of them, or all excepting the variety of P. paupercu-

lum, were taken on the west beach side in the Workhouse Point cross-

section. Only the two of them least reputed previously for sensitive-

ness, P. coinprcssinn and Campcloin-a subsolidum, were found in the

channel or eastward of it below Peoria Narrows: and none of them

was taken at stations more than 500 feet to the eastward of the mid-

channel line or .south of the upper and cleaner third of the lower lake.

Numbers per collection or per unit of bottom area were small and

relatively unimportant in all cases.



375

While the comparison with variety and abundance in the same
group in the middle lake in 1922 was distinctly unfavorable, that with

the lower lake in the summer two years before, particularly in the

case of the Pisidia, was less so, and suggests moderate improvement

within the limited area of best conditions in the two years. Besides

taking in 1922 one more species than we did in 1920, one or the other

of the two species of that genus was found at five in all of the total

of eighteen stations visited in 1922; whereas in the summer of 1920

only a single species of the genus {P. comprcssuui) was taken, and it

was confined to a single station in the Peoria Narrows cross-section.

No explanation of the reduction in variety in this group between

the middle and lower lakes recently is furnished by the comparison

with our 1913 and 1915 data. In those years we took as many kinds

and as great average numbers of Pisidium in the lower as in the middle

lake, and more kinds of Sphaerium in the lower lake than in either

the middle or upper; and found as well species of both genera at the

wide-water stations in the lower half of the lower lake, where they

were not taken at all either in 1922 or 1920. In view of these facts,

though based in some cases on few collections, it is difficult to avoid

the conclusion that local pollution has been injurious to this group in

lower Peoria Lake recently.

LESS TOLERANT ASSOCIATED GROUP

A group of seven miscellaneous species having at first sight no

characteristics in common except the fact that none of them was taken

above the lower lake cither in 1922 or 1920 completes the list of lower

lake bottom animals taken by us in the season of 1922. Of this group

three appeared in 1922 that were not found in collections in 1920, and

three inl920 that were absent in 1922, giving us seven representatives

of the lot in each summer's collections. The list included, as taken

either in 1922 or 1920, the following species, embracing insects other

than Chironomidac
;
young mussels

;
pleurocerid snails ; sponges ; bry-

ozoans ; and Crustacea :

1922 only.

Corixa species.—Peoria Narrows, in strong current.

Lcptocerid (caddis) larva.—Peoria Narrows, in strong current.

Anodonta iiiibeeillis .Say.—Mid-channel, opposite l-'ulton Street,

Pforia. in current.



1922 and 1920.

Goniobasis livescens Menke.—P. P. U. Bridge, in strong current.

Sponge species.—Peoria Narrows, in strong current, 1920; op-

posite Fulton Street, Peoria, 1922, 600 feet east of mid-channel, in

current greater than that outside of channel in middle or upper lake.

Hyalella knickerbockeri (Bate).—In or near channel, several sta-

tions, both 1923 and 1920, in current; once in far wide-waters, 1920.

near edge of smartweed bed.

Plumatclla pr'mccps var. fniticosa Kraepelin.—Peoria Narrows

and P. P.. U. Bridge in strong curent, and just outside of channel op-

posite Liberty Street, 1920; mid-channel and 600 feet east, opposite

Fulton Street, 1922.

1920 only.

Quadrula plicata Say, young.—Peoria Narrows only, in strong

current.

Plcuroccra clcvatuiu var. Iczi'isii Lea.—Peoria Narrows and P. P.

U. Bridge, in strong current.

Hydropsyche species.—Peoria Narrows and P. P. U. Bridge, a

strong current.

Evidently an important consideration about this otherwise motley

group is that ail but one of them were confined both in 1922 and 1920

either to the swifter water at Peoria Narrows or the P. P. U. Rail-

way Bridge, slightly above and below the lake proper ; or were con-

fined if taken in open lake cross-sections to the first 600 feet eastward

of the mid-channel line, where also the current is appreciably greater

than in corresponding locations in the upper and middle lakes. Be-

sides this, the little fresh-water shrimp, Hyalella, which was found

once in the east wide-waters near the edge of a smartweed bed, as

also the species of Corixa, are really not bottom forms in the strict

sense, being both free swimmers to a considerable extent and. in the

case of the corixids, coming to the surface occasionally for air.

In favor, on the other hand, of a higher degree of tolerance in

all members of this group than that jiossessed b)- the recently extermi-

nated mussels, snails, and other bottom species of all three lakes is

the fact that they have survived in recent years where so many other

species have perished. Such a supposition receives support from our

records from the polluted waters of the upper Illinois River obtained

in the years 1911 and 1912 (Forbes and Richardson, 1913). At that

time the identical species in the case of five of the 1920-1922 list



(Quadrula plicata, Pleuroccra elevatum, var. lewisii, Goniobasis livcs-

ceiis, Hyalella knickerbockeri, Plumatella princeps, var. fniticosa*,

and species closely allied in three other cases) were taken at stations in

the polluted sections of the upper Illinois where surface dissolved

oxygen ranged between 1.4 and 2.7 parts per million, and where the

great bulk of the normal bottom population had already been destroyed.

One of the .snails, also, Pleuroccra elcvatum, was one of the only two

snails taken by Jewell in the acid waters of the Big Muddy River in

southern Illinois in 1919 (Jewell, 1922).

Comparison of the Recent Small Invertebrate Bottom
and Weed Fauna of Peoria Lake with that of

1913-1915.

GENERAL COMPARISON

Pre-] 930 records of the bottom fauna, including the mussels, from

the section of the Illinois River covered in the present paper were

made by us at Chillicothe in the autumn of 1911 and the sinnmer of

1912; and collections of the smaller bottom species only were made

in a series of cross-sections between Chillicothe and the foot of lower

Peoria Lake in the summers of 1913 and 1914 (Forbes and Richard-

son, 1913 : Richardson, 1921). In addition to this earlier work of our

own, the United States Bureau of Fisheries made a survey of the

mussel resources of Peoria Lake, in connection with one of the entire

Illinois River, during the years 1911 and 1912 (Danglade, 1914).

In making comparisons with these earlier records it is not possible

always to be as exact as one could wish, because determinations were

not carried out in as much detail in the earlier period as has been

the case with more recent collections. For this reason, and also be-

cause of the necessarily very small fraction of the total bottom area

covered by dredge hauls, neither our lists of the earlier nor the more

recent bottom species of the lake are assumed to be as complete as they

might have been with heavier programs of dredgings. Previous ex-

perience in dredging in the Illinois River and in other wa'.ers in Illi-

nois has shown, however, that the number of bottom species that may

be expected in single hauls is never very large, apparently as a con-

sequence of a general rule that one or two or at the best a few species

tend to iiredominate, usually with great distinctness, in a given range.

• At that time Incorrectly Identified.



378

In view of this fact, added to the generally rational and therefore

explicable nature of the results, it seems not unreasonable to suppose

that in the total of one hundred and fifty-two hauls in Peoria Lake

between 1913 and 1923 (46 in 1913-1915, as a part of a total of 387

for the entire river; and 106 in 1920-1922) we probably obtained in

both periods examples of at least most of the commoner species inso-

far as these are present during the summer season.

As all subdivisions of Peoria Lake were well supplied with coarse

aquatic vegetation over a large portion of their area up to 1915, in

order to obtain fair comparison with our 1920 and 1922 records, w-hich

were made after the old weed-beds had been destroyed, it has been

necessary to exclude a good many of the less distinctly bottom forms

of the pre-1920 lists. The exclusions cover a sizable assortment of

free-swimming, weed-dwelling, and air-breathing species, not belong-

ing in a proper sense to the bottom, which formerly entered in con-

siderable numbers into bottom collections made in the shallower areas

where there was more or less vegetation. Most of the excluded forms,

it may be noted, have also disappeared since nine or ten years ago,

along with the vegetation, over practically the entire area of Peoria

Lake.

Having regard at present, then, only to the more exclusively

bottom-species, both in the case of the earlier and the more recent

records, we find that we took as nearly as may be calculated a total

of 22 or more kinds in the upper lake in 1913-1915, of which at least

8 have since disappeared ; 26 or more species in the middle lake, of

which 12 have since dropped out ; 43 or more species from the lower

lake, of which 19 have disappeared ; and from the bottom muds of

all three lakes combined no less than 61 species, of which at least 23

are missing in recent collections, although recent hauls have been more

than double the number of the earlier ones.

In evident contrast with the reduction of representation in the

lists of more sensitive species, the tabulation (p. 383) indicates good-

sized additions in all three lakes to the totals of more tolerant kinds

since 1915. While a part of these apparent additions in the ix)llu-

tional or tolerant column have undoubtedly taken place, especially in

the Tubificidae and Chironomidae, it is probable that the more complete

identification of the more recent material accounts for a part of them.

It is, however, quite certain that there has been large increase in

numerical abundance since 1915 of some of the more pollutional forms.



379

Of interest also is the apparent indication of a larger variety of

bottom species in the lower lake than in the upper or middle lake be-

fore 1920, and a correspondingly greater loss of kinds in the lower

lake species lists between 1915 and 1922. It is quite posisble that the

upper and middle lakes may have been injured to a minor extent by

sanitary canal pollution before 1915 and in advance of serious injury

to the lower lake from the same or local causes. But this can not

now be proven, and the continued existence of a healthy and varied

mussel fauna (see page 3S.-)) between Peoria Narrows and Chilli-

cothe as late as 1!)15, is against assuming that there had by that time

been any very serious change, at least in the channel, in or quite near

to which the mussel beds have always been located.

The greater variety of habitats furnished by the lower lake and

its connections, already mentioned, may account for a good deal of

the difference shown
; and some of it may result from the greater num-

ber of lower lake bottom collections in the earlier jieriod, including

fuller special studies on the Chironomidae there than elsewhere, in

the course of short visits by Malloch to Peoria in liHli and 1914 ( Mal-

loch, 1915). But as si)ecial evidence suggesting earlier injury, par-

ticularly to the wide waters of both the upper and middle lakes, where

sedimentation after the spring floods is particularly heavy, may be

mentioned the noticeable absence or extreme rarity in the 191.3-1915

collections of several groups of insects; such as the commoner aquatic

Coleoptera ; various Odonata; and from the upper lake in particular,

the common May-fly nymph of the genus Hexagenia, as well as other

Ephemeridae. The limited amount of collecting in the vegetation

zones before 1920 also showed much poorer results than were easily

to be obtained at that time with the .same amount of effort in the lakes

possessing similar aquatic vegetation near Havana.

COMMONER SMALL BOTTOM ANIMALS THAT HAVE
nrSAPPEAKED SINCE 1915

While reviewing the missing members of the old fauna, it will be

recalled that the species obtained in Peoria Lake in 1922 and 1920

have already been arranged, in this and earlier ])apers in a descend-

ing order of tolerance without so far disclosing any that seem to have

a clear title as clean bottom species. The subjoined lists may be sup-

posed, on the contrary, to include a considerable number of kinds that

fall fairly under that designation, so far as they are applicable at all



380

to the inhabitants of the bottom muds of our larger streams under

present-day conditions.

PLANARIANS

Various unidentified species of planarians, attached to shells, bits

of bark, leaves, etc., were not uncommon in Peoria Lake bottom hauls

in years previous to 1930. These did not appear in any of our 1920

or 1922 bottom dredgings, or on any of a quite large number of dead

mussel shells examined in the summer of 1920, although a few were

noted in sediment samples caught in the relatively fast current at

Peoria Narrows in August 1923 by a machine set about eighteen inches

above the bottom.

BRYOZOA

While only a single species of bryozoan, Plutnatella prin-ceps, var.

fruticosa, was found in Peoria Lake bottom collections in 1920 or 1922,

two other species, Paludicella ehrcnhergii Van Beneden and Uniafclla

gracilis Leidy, were common on live or dead shells in the deeper water

everywhere below Chillicothe up to the summer of 1915. On many

of the mussel shells examined in the summer of 1920 there were marks

apparently left by the attachment of former colonies of these species.

SNAILS

The list of snails missing since 191.5 includes two conspicuous

cases of large and abundant kinds which were formerly so common
in collections nearly everywhere in the lake that they gave their char-

acter largely to the majority of hauls made between Chillicothe and

Peoria in 1913 and 1915. These were Vivipara contectoides W. G.

Binney and Lioplax subcarinatus Say.

Species of snails that occurred in smaller numbers, but which

seem to be of scarcely less importance as index organisms, include a

second large species of Vivipara, V. subpurpurca Say, which was taken

several times in the earlier collections, only in the middle and lower

lakes, and principally in the lower. Notable also, up to 1915, vvas the

little Amnicola cmarginata Kiister, which, although not widely dis-

tributed, occurred before 1930 in fairly large numbers over limited

areas in both the middle and lower lake.

Two species of Valvata, V. tricarinata Say and V. bicarinata Lea,

were formerly not far from equally common in the wide waters of

the first two of the lakes. The first one was taken in a single haul



381

also in the summer of 1932 within less than a hundred feet of the bank

at the lower end of the upper lake, but the other appeared in none of

our collections from anywhere between Chillicothe and Peoria in 1930

and 1922. These two species, while evidently partial to shallow weedy
waters, also habitually spread far from shore in our local bottomland

lakes; occurring in lakes near Havana in 1914 and 1915 in six to

nine feet of water on plain mud bottom, and in the four to seven foot

depth zone in upper Peoria Lake before 1930. A species of Ainnicola

near A. liiiwsa Say, partaking of the habit of the Vaivatas just de-

scribed, of becoming bottom or weed species at will, was taken in the

shallower areas of the upper and middle lakes before 1920.

Other bottom-dwelling snails taken in Peoria Lake in 1913 and
191.") collections but since then not seen, included one or"more species

of the little lini]X't-like .'Xncylus, which was formerly common on shells

and sticks in the deeper water near the channel; a species of Pleuro-

cera, P. sitbularc Lea, which occurred less commonly than its more

abundant congener, P. clcvatum lennsii, which latter species still per-

sists in small numbers in the more rapid current in the lower lake

;

and the comparatively large amnicolid Somatogyriis siibglobosus Say,

which was taken in small numbers only in the upper lake.

INSECTS

Among larvae and nymphs of insects which have recently disap-

peared entirely from open-water dredgings in all three lakes the most

important are members of the family Ephemeridae, or May-flics; of

several families of Odonata, or dragon-flies ; and of the commonest

of the midge families locally, the Chironomidae.

In 1913 and 1915 the common May-fly, Hexagenia variabilis

Eaton, was occasional in collections from both the middle and lower

lakes, but has not since been taken in the Illinois River above Havana.

Specimens of two other genera of May-flics that have since failed to

appear, Callibaetis and Caenis, were also taken several times in the

course of the dredging before 1980 in the two lower lakes.

The principal Chironomidae that have disajipearQd include Ciii-

ronomus tentans Fabricius, formerly one of the most generally dis-

tributed and abundant, and because of its large size most conspicuous

of the midge larvae of Peoria Lake and other middle Illinois River

situations during the summer season. Other larval midges definitely

missing recently, include Chironomus nigricans Johannscn ; one or more



382

species of the genus Cricotopus ; and a species of the genus Ortho-

cladius.

Several unidentified species of at least three families of dragon-

flies, whose nymphs have no green or other bright color*, are for the

present admitted to the list of bottom forms that have disappeared

from Peoria Lake' since eight or ten years ago although some members

of this group have recently been found to be unusually tolerant.

Stickney (1922) found Libellida pulchcUa Drury very tolerant to con-

ditions of low oxygen in recent experiments at Urbana ; and Baker

(1923) took the same species in the comparatively foul muds of the

Big Vermilion at St. Joseph, where all the mussels had been killed.

The writer took Chromagrion condittini Hagen and Platythcmls lydia

Drury in the; Kishwaukee River below De Kalb in February 1922 in

water polluted by acid wa.stes from steel mills to such an extent that

most of the normal bottom fauna had been driven out or destroyed.

The disappearance of nymphs of this group recently in the Peoria

district may have been more in the nature of an indirect effect of the

destruction of the vegetation, which served as headquarters for the

adults, than evidence in all cases of unusual sensitiveness.

* Some green nymphs of the family Airrionidae have been excluded, as weed

species, from the present comparison.



383

Number of Species of Small Bottom Animals Taken in Peokia Lake,
1913-1915 TO 1920-1922. All Zones Comhined; Accidental Wf:ed

and Surface Forms Excluded; no Duplications



384

ALMOST COMPLETE EXTINCTION OF AN ABUNDANT AND
VARIED MUSSEL FAUNA SINCE 1913-1915

If we add to the list of exterminated small bottom animals the

most of the mussels found by Danglade (1914) in Peoria Lake in 1911

and 1912, and now apparently all gone but an inconsequential number

of the hardier species in the lower lake, this addition raises the total

of missing bottom species from more than twenty to more than sixty

kinds. Danglade listed in all, from the three lakes, a total of forty-

one species, of which twenty came from Chillicothe and thirty from

the middle lake. The number of kinds taken in the lower lake was

not stated. The location of the most important commercial mussel

beds as described by Danglade as they existed in 1911-1912, included

beds above and below Rome : a mile above' Spring Bay and in Spring

Bay Narrows ; below Mossville ; and between Al Fresco Park and

Peoria Narrows. The continued existence in good condition of the

Mossville and Al Fresco Park beds, and of a vast bed of bluepoints.

(Ouadnda plicata) more than two miles long in the lower lake, extend-

ing from the center of the channel eastward, was verified by sketch

maps furnished us as late as November 1915 by Havana pearl-hunters

who spent the summer and fall of 1915 in Peoria Lake.

In the summer of 1930 and of 1922 we took with the Petersen

dredge a single specimen each in the lower lake of two species, but no

trace of live mussels of any kind in the waters above Peoria Narrows.

We also, in July 1920, went carefully over a small boatload of mussel

shells taken with a dip-net the same day by a Peoria musseler who we

thought must have a market for dead shells to justify the otherwise

unproductive work that he was doing. The number of shells we

found alive was extremely few and all belonged to one or the other of

two species, the bluepoint, Ouadrnla plicata; or the warty-back, Quad-

rtiki pHsltilosa. It is significant that both of these species were taken

by us farther north in the polluted upper Illinois River in the summer

of 1912 than any other mussels with the exception of one species

{Sympltyiiota cuinplanata) ; the first having been taken at Starved

Rock in company with 5". complanata; and the second at Spring Valley.

The list of Peoria Lake mussels as of 1911-1913 that follows is

as presented by Danglade (191-i), except for the starring of the two

unusually tolerant species of Quadrula above noted, and of theappar-

ently hardy dwarf species of Anodonta which wc took with the Peter-



385

sen dredge in the lower lake in the summer of 1922. The fact that the

full Danglade list for Peoria Lake, inclusive of Chillicothe, of forty-

one species, was only eight short of his complete list of forty-nine

kinds for the entire Illinois River in 1911-1912 does not suggest that

the channel areas of Peoria Lake had been seriously injured up to

that time, although the Chillicothe list had already apparently suffered

some reduction.

Mussels Reported by Danglade (1914) from Peoria Lake, Inclusive

OF Chillicothe, in 1911-1912, but wmcii Appear to ha\-b Since

BEEN C0>IPLETELY EXTERMINATED ABOVE PeORIA NaUBOVPS, AND
TO HAVE Nearly All Perished in the Lower Lake

The three species of which we obtained records in the lower lake in 1920

and 1922 are starred; those taken or seen by Danglade both at Chillicothe

and in the lake below there, or at Chillicothe only, are marked with a C.

No. 16 was taken at Chillicothe only.

1. Quadrula granifera. C
2. Quadrula ebena. C.

3. Quadrula plena

4. Quadrula solida

5. Quadrula coccinea

6. Quadrula obliqua

7. Quadrula trigona.

8. Quadrula rubiginosa

*9. Quadrula pusiulosa. C
10. Quadrula fragosa

11. Quadrula lachrymosa. C

12. Quadrula metanevra

13. Quadrula heros. C
14. Quadrula undulata. C

•15. Quadrula plicata. C
16. Unio crassidens. C
17. Unio gibbosus. C
18. Symphynota complanata

19. Arcidens confragosus. C

20. Anodonta corpulenta

21. Anodonta suborbiculata

*22. Anodonta imbecilis

23. Strophitus edentulus

24. Obliquaria reflexa. C
25. Tritigonia tiiberculata

26. Plagiola donacitormis

27. Plagiola elegans

28. Plagiola securis. C
29. Obovaria ellipsis

30. Lampsilis laevissima

31. Lanip.silis gracilis. C
32. Lampsilis alata

33. Lampsilis parva

34. Lampsilis recta, C
35. Lampsilis fallaciosa.

36. Lampsilis anodontoides

37. Lampsilis higginsi. C
38. Lampsilis orbiculata. C
39. Lampsilis ligamentina. i

40. Lampsilis luteola. C
41. Lampsilis ventricosa



BIBLIOGRAPHY
Baker, P. C.

'22. The niolluscan fauna of the Big Vermilion River. Illinois, With
special reference to its modification as a result of pollution by
sewage and manufacturing wastes. 111. Biol. Monographs, VII, No.

2, p. 1-127.

Danglade, Ernest

'14. The mussel resources of the Illiuois River. Report U. S. Commis-
sioner of Fisheries for 1913, Appendix VI. p. 1-4S and plates.

Forbes, Stephen A., and Richardson, R. E.

'13. Studies on the biology of the upper Illinois River. Bui. 111. State

Lab. Nat. Hist., 9 (Art. X) : 481-574 and plates.

Jewell, Minna E.

'22. The fauna of an acid stream. Ecology, III, No. 1, Jan., 1922, p.

22-28.

Juday, Chancey
'08. Some aquatic invertebrates living under anaerobic conditions.

Trans. Wis. Acad. Sci. Arts and Letters, 16 (Pt. I): 10-16.

Malloch. John R.

'15. The Chironomidae. or midges, of Illinois, with particular reference

to the species occurring in the Illinois River. Bui. 111. State

Lab. Nat. Hist., 10. (Art. VI) : 275-543 and plates.

Muttkowski, R. A.

'18. The fauna of Lake Mendota: a qualitative and quantitative survey,

with special reference to the insects. Trans. Wis. Acad. Sci. Arts

and Letters. 19 (Pt. I): 374-482.

Richardson, R. E.

'21. The small bottom and shore fauna of the middle and lower Illi-

nois River and its coniiectin.g lakes, Chillicothe to Grafton: its

valuation; its sources of food supply; and its relation to the

fishery. Bui. 111. Nat. Hist. Survey, 13 (Art. XV): 363-522 and

charts.

'21a. Changes in the bottom and shore fauna of the middle Illinois River

and its connecting lakes since 1913-1915 as a result of the in-

crease, southward, of sewage pollution. Bui. 111. Nat. Hist. Survey,

14 (Art. IV): 33-75.

Stlckney, Fenner
'22. The relation of the nymphs of a dragon fly {LibeVnla puU-hrUn

Drury) to acid and temperature. H^cology, III. No. 3, July, 1922,

p. 250-254.



388

Suter, Russell, and Moore, Emmeline
'22. Stream pollution studies. State of New York, Conservation Com-

mission, p. 1-34.

Weston, Robert Spurr, and Turner, C. E.

'17. Studies on the digestion of a sewage-filter effluent ty a small and

otherwise unpolluted stream. Contrib. from the Sanitary Research

Laboratory and Sewage Experiment Station, Massachusetts In-

stitute of Technology, 10: 1-96, and plates.



COMPARISON OF 1922 AND 1920

SPECIES LISTS, DETAIL





axAa Aifloas naqiu -.grvsu aai')::

.tlrt D'.'iiiin'

I'i'tDl a\)bint ) I

««i»>v* uo

.qqe lo .r, .qqa 10

Xsa muBiovanjjiJ mtiiiu- i-'-

btixuAt'ion J»')rtJtu\ ,3/

T.noiDnA

.»««o^«l«,».^ -.^.^

PRINTED BY AUTHORITY OF THE STATE OF ILUNOIS

URBANA. ILLINOIS

October. 1925



Ati, Zonks

1932; 2S stations
ssaectlons

POLLOTIONAI, MORE TOLEKANT, OR DOUBTFUI.

Wormi (,Tuhifici<!ac and Xaididae)

Limnodrilus hoftmeistori Claparfide

Umnocirilus n. sp.*

Tubitex tubif« {JluUer) ? or var.

Limnoiirilus sp. like L. claparede-

iauus Ratzel

Naidiiiae. iinidentifleil

5

At least 3 or 4 spp., unldpntlfled

3+

Erpobdella punctata (Leidy)

Helobdella nepheloidea (Grat)

Leeches

One unidentified species

PolUitional or more tolerant midge larvae

Cliironomus plumosus Linnaeus, var. Chironomus plumosus Linnaeus

Chironomus decorus Johannsen
Tanypus dyari Coquillett

3

Midge larvae of doubtful status

Chironomus sp. or spp.

Procladius sp. or spp.

Tanypus sp. or spp.

Tanypus monilis Linnaeus

4+

Chironomus sp. or spp.

Tsmypus sp. or spp.

2+

Vnusually tolerant snails

Musculium transversum Say
{
Musculium transversum Say

1
!

1

LESS TOLERANT GEOHP (SNAILS ONLY)

Less tolerant stuiils, first group, (upper lake, farthest northward
occurrence, 19B2)

Musculium truncatum Linsley I Campeloma subsolidum Anthony
Pisidium compressum Prime
Pisidium pauperculum, var. crystal-

,

ense Sterk;

Pisidium sp. near complanatum
Sterki

Campeloma subsolidum Anthony
6

CLEANEB WATEE OR LESS TOLEEANT ASSOCLATED GEOUP
Mussels



ajiAj Aifloaa mjuuim

q(7H [i=.t1li I Or.il .ir!;-il,,^il,.i. I

solMqs bsBt

aiuJj;

f1inr>>

)« Bllabdol^a

aaacnaiJ auRotaulq buu:

JJe!

.%• .auMOfliJ airaotnuiq 8i<

.qq» 10 .Q':

.qqa ie

(88 fnu<!i9

(tjvio k .

xnodlaA luuhilucuJui) fiuioUq.;

PRINTED BY AUTHORITY OF THE STATE OF ILUNOIS

URBANA. ILLINOIS

October, 1925



COMPARISON OF SPEt'IKS LISTS; MIDDLE PEORIA LAKE

Whmc WATiuia

1 ; . I osasGCtions 1920: 8 stations; 2 cross-sections

I'OM.ITIONAL, MOKK TOIJatAST, OR DOUBTFUL

lVor»is {TubificUItie and Naididae)

Limnodrilus hoffmeisteri Claparfide

Limnortrilus n. sp.

Tubifcx tubifex (Miiller)? or var.

Naididae. unidentified

Other uuidentitled, immature

4+

At least 3 or 4 spp., unidentified

3+

Helobdella nepheloidea (Graf)

Helobdella stagnalis (Linnaeus)

Leeches

Unidentified species

PoUutional or more tolerant midpe larvae

Chironomus plumosus Linnaeus, var. Chironomus plumosus Linnaeus

Chironomus plumosus Linnaeus, var.

Tanypus dyari Coquillett

3

Midge larvae of douitful status

Chironomus sp. near C. maturus

Johannsen

Chironomus digitacus Malloch

Chironomus sp. or spp.

Procladius sp. or spp.

Tanypus sp, or spp.

5+

Chironomus sp. or spp.

Tanypus sp. or spp.

2+

Unusually tolerant snails

Musculium transversum Say Musculium transcersum Say
1

I

1

LESS TOLERANT GEOITP (SNAILS ONLY)

Less tolerant snails, first group, (upper lake, farthest northward
occurrence, 1922)

Campeloma subsolidum AnthonyMusculium truncatum Linsley

nsiiirum e<-/rapT"<???inrrTTTTTT^

Pisidium pauperculum, var. crj'stal-

ense Sterkl

Pisidium sp. near P. complanatum
Sterki

Campeloma subsolidum Anthony
5

Less tolerant snails, second group, (middle lake, farthest north-

ward occurrence, 1022)

Pisidium pauperculum Sterki

Pisidium sp. like P. sp. from L.

Winnebago, Sterki

Pisidium sp. unidentified. Sterki

Sphaerium stamineum Conrad
Sphaerium striatinum, var. lilycash-

ense Baker

5

MusieU

HnaiU

Bryozoa

Sponges

Crustacea

CLEANER WATER OR LESS TOLERANT ASSOCIATED GROUP

Mussels

Snails

Bryozoa

Sponges

Crustacea

Other insects than midges

Total 23+

Other insects than midges

Total 11+

1922: 27 stations; 3 cross-sections 1920: 6 stations; 2 croBS-sections

POLLUTIONAL, MORE TOLERANT, OR DOURTFTJL

Worms (Tuhiflcidae and Naididae)

Limnodrilus hoffmeisteri ClaparSde

Limnodrilus n. sp.

Naididae. unidentified

Other unidentified, immature
3+

At least 3 unidentified spp.

Helobdella nepheloidea (Graf)

Helobdella stagnalis (Linnaeus)

Leeches

Unidentified species

PoUutional or more tolerant midge larvae

Chironomus plumosus Linnaeus, var.

Midge larvae of

Chironomus sp. near C. maturus
Johannsen

Chironomus digitatus Malloch

Chironomus sp. or spp.

Procladius sp. or spp.

Tanypus sp. or spp.

5+

Chironomus plumosus Linnaeus
Chironomus plumosus Linnaeus, var.

Tanypus dyari Coquillett

3

doubtful status

Chironomus sp. or spp.

Tanypus sp. or spp.

2+

Unusually tolerant snails

Musculium transversum Say I Musculium transversum Say
1

I

1

LESS TOLERANT GROUP ( SNAILS ONLY)

Less tolerant snails, first group, (upper lake, farthest northtvard

occurrence, 1022)

Musculium truncatum Linsley Campeloma subsolidum Anthony

Pisidium compressum Prime
FibHliuin ijauporculum, var ory^rtnl-

ense Sterki

Pisidium sp. near P. complanatum

Starki

Campeloma subsolidum Anthony

5

Less tolerant snails, second group, (middle lake, farthest north-

ivard occun-ence, 1022)

Pisidium pauperculum Sterki

Pisidium sp. unidentified, Sterki

Sphaerium stamineum Conrad

Sphaerium striatinum, var. lilycash-

ense Baker

4

Mussels

Snails

Bryozoa

Sponges

Crustacea

LESS TOLEItANT ASSOCIATED GROUP

Mussels

Snails

Other insects than midges

Total 21+

Bryozoa

Sponges

Crustacea

Other insects tha7i midges

Total 11+

1922: 3 stations; 3 cross-sectlonB 1920: 2 stations; 2 cross-sections

POIXUTIONAI,, MORR TOLERANT, OR DOUBTTUL

Worms (Tubificidae and Naididae)

Limnodrilus hoffmeisteri Claparfede
Limnodrilus n. sp.

Tubifex tubifex (Miiller) or var.?

Naididae. unidentified

4

At lea«t 3 unidentified spp.

Leeches

3

Leeches

I

Leeches

PoUutional or more tolerant midge larvae

Chironomus plumosus Linnaeus, var.
|
Tanypus dyari Coquillett

1
1

1

Midge larvae of doubtful status

Chironomus sp. or spp.

1

Chironomus sp. or spp.

1

Unusually tolerant snails

Musculium transversum Say i

1

LESS I-OLERANT GROUP (SNAILS ONLV)

Less tolerant snails, first group, (upper lake, farthest northward
occurrence, 1022)

Pisidium compressum Prime
Pisidium sp. near P. complanatum

Sterki

Less tolerant snails, sec07id group, (middle lake, farthest nortJi-

ward occurrence, 1022)

Pisidium sp. like P. sp. from L. Win-
nebago, Sterki

Sphaerium striatinum. var. lilycash-

CLEANEa WATER Oil LESS TOLEILiST ASSOCIATED GROUP

Mussels



•IMAJ AI>f"'"l ' !}/>< I t-IVII >M|-.'J<1^

.qqa bsBliii

( /!;!'(. I "l ';ij;i-.i111tl li\l'>h'

(-11

f villi.! I !;ll»l^iiJllll :ill iliil,.ii iM

I ll.iV>) ii-Jl'MU

3trTnf:i.T ti 1/(1 "irnrTfinmiri'

>litl,\v \uH.\,i,,\, ^,, ,l,'i->i,\ 'i..\,i\f

i\,r. !ri(ir.'i^v<;iniT ) iiiiiii ii'>-im/. IIUJ'^ I'.' /run. I 1 in W I I li 'II

PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS

URBANA. ILLINOIS

October. 1925



All Zonks

COMl'AUIHON OK yPEc:iIi:s LISTS; LOWKR PEORIA LAKE

WUTE WaTEBS

1922: IS Btatious: 3 cross-sections 1920: 19 atatlons; 6 cross-sectiona 1922: 14 stations; 4 cross-sections 1920: 14 stations; B croas-sectlons

rOia.l)T10NAI^ MOKE TOLKKANT, OR DOUllTFUL

Worms (Tuhificidac and Naididae)

Linmodrilus hoffmeistori ClaiiarSde

Limnodrilus n. sp.

Tubifex (ubifex (Miiller) or var.?

New genus

Other unidentified, Immaturo

4+

At least 3 unidentified spp.

3

Erpolidella punctata (Leidy)

Helobdella staEnalis (Linnaeus)

Helobdella nepheloidea (Graf)

Dina parva Moore

4

Leeches

Erpobilella punctata (Leidy)

Helobdella stagnalls (Linnaeus)

Pollutional or more tolerant midge larvae

Chironomus plumosus Linnaeus

Chironomus plumosus Linnaeus, var.

Cbironomus maturus Jobannsen

Chironomus plumosus Linnaeus
Chironomus plumosus Linnaeus, var.

Chironomus maturus Johannsen
Chironomus frequens Johannsen
4

Midue larvae of doubtful status

Chironomus digitatus Malloch

Tanypus monilis Linnaeus

Chironomus sp. or spp.

Procladius sp. or spp.

Tanypus sp. or spp.

Chironomus crasslcaudatus Malloch
Palpomyia longipennis Loew?
Chironomus sp. or spp.

Tanypus sp. or spp.

4+

Unusually tolerant snails

Musculium transversum Say i MuscuHum transversum Say
1

I
1

LESS TOLEltANT GROUP ( SNAILS ONLY)

Less tolerant snails, first group, (upper lake, farthest northward
occurrence, 1922)

Pisidmm compressum Prime
Pisidium pauperculum, var. crystal-

ense Sterki

Campeloma subsolidum Anthony

Pisidi

Camp'
:'m f'ninr

uiiini Anihdiiy

Less tolerajit snails, second group, (middle lake, farthest north-
ward occurrenee, 1922)

Sphaerium stamineum Conrad
I Sphaerium slaminsum Conrad

^
I

1

CIJIAXER WATKB OK LESS TOLERANT ASSOCL\TED GROUP

Mussels

Anodonta imbeeiUis Say
j

Quadrula plicata Say

Goniobasis livescens Menke

1

Snails

Goniobasis livescens Menke
Pleurocera elevatum, var. lewisii Lea
2

Plumatella princep.s. var. fruticosa
Kraepelln

1

Bryozoa

Plumatella princeps, var. fruLicosa
Kraepelin

1

l-'nidentified species

1

Sponges

I

Unidentified species

1

Crustaeea
Hyalella knickerbockerl (Bate)

I Hyalella knickerbockeri (Bate)

I
1

Other inseets than midges
Caddis larva (Leptoceridae)
Corlxld nymph
2

Total 28+

Hydropsyche sp.

1

Total 24+

POLLUTIONAL, MORK TOLERANT, OR DOUBTFUL

M'orms [Tubificidae and Naididae)
Limnodrilus hoffmeiateri Clapar^de
Limnodrilus n. sp.

Tubifex tubifex (Muller) or var.?

New genus

Other unidentified, Immature
4+

At least two unidentified spp.

Erpobdella punctata (Leidy)

Helobdella stagnalls (Linnaeus)
Helobdella nepheloidea (Graf)

Dina parva Moore
4

Leeches

Erpobdella punctata (Leidy)
Helobdella stagnalis (Linnaeus)

Pollutional or more tolerajit midges

Chironomus plumosus Linnaeus, var.

Chironomus maturus Johannsen
Chironomus plumosus Linnaeus

Chironomus plumosus Linnaeus
Chironomus plumosus Linnaeus, var.

Chironomus maturus Johannsen
Chironomus frequens Johannsen
4

Chironomus digitatus Malloch

Tanypus monilis Linnaeus
Chironomus sp. or spp.

Procladius sp. or spp.

Tanypus sp. or spp.

5+

Midge larvae of doubtful status

Chironomus crasslcaudatus Malloch
Palpomyia longipennis Loew?
Chironomus sp. or spp.

3+

Unusually tolerant snails

Musculium transversum Say i Musculium transversum Say
1

I

1

LESH TOLRRANT GROUP (SNAILS ONLY)

Lrs.-i tulrrtijit stiails, first group, (upper lake, farthest northward
oeCMrrewce, 1922)

r i' -.-nin Prime
b^iilidum Anthony

Pisitliuni compressum Prime

Pisidium pauperculum, var. crystal- C...

ense Sterki

Campeloma subsolidum Anthony

3

Less tolerant snails, second group, (middle lake, farthest north-

ward oecurrence, 1922)

Sphaerium stamineum Conrad I Sphaerium stamineum Conrad

1 I
1

CUOANER WATER OR LESS TOLERANT ASSOCIATED GROUP

Mussels

I Quadrula plicata Say

1

Goniobasis livescens Menke

1

Snails

Goniobasis livescens Menke
Pleurocera elevatum, var. lewisii Lea

2

Bryozoa

Plumatella priuceps, var. fruticosa

Kraepelin

1

Plumatella princeps, var. fruticosa

Kraepelin

1

Unidentified species

1

Sponges

I

Unidentified species

I
1

Orustacea

Hyalella knickerbockeri (Bate) Hyalella knickerbockerl (Bate)

1 I 1

Other insects than midges

Caddis larva (Leptoceridae) Hydropsyche sp.

Corlxid nymph
2 1

Total 27+

ClIASNEt^

1922: 4 stations; 4 cross-flections 1920: 5 stations; 6 crowMwctUnui

POIiUTIONAL, MORi; TOLERANT, OB DOUItTFXJI.

Worms {Tubificidae and Naididae)

Limnodrilus hoffmeiateri ClaparMe
Limnodrilus n. sp.

Unidentified

3

At IcaHt 3 unidentified spp.

3

Leeches

Helobdella stagnalis (Linnaeus)

Helobdella nepheloidea (Graf)

Dina parva Moore

Pollutional or more tolerant midges

j
Chironomus plumosus Linnaeus
Chironomus plumosus Linnaeus, var,

Chironomus maturus Johannsen
Chironomus frequens Johannsen
4

Millar Inrviic nf thtuhfful xinlus

Chironomus sp. or spp.

1

Chironomus sp. or spp.

Tanypus sp. or spp,

Chironomus crasslcaudatus Malloch

3+

Unusually tolerant snails

Musculium transversum Say [ Musculium transversum Say
1

!

1

LESS TOLERANT GROUP (SNAILS ONLY)

Less tolerant snails, first group, (upper lake, farthest 7iorthward

occurrenee, 1022)

Pisidium compressum Prime
|
Campeloma subsolidum Anthony

Campeloma subsolidum Anthony
2

I

1

Less tolerant snails, second group, (rniddle lake, farthest north-

ward occurrence, l[i~^)

— --

j

Sphaerium stamineum Conrad

I
1

CLEANER WATER OR LESS TOLERANT ASSOC'LiTED GROUP

Mussels

Anodonta imbecillis Say

1