Bulletin


STATE OF ILLINOIS

DEPARTMENT OF REGISTRATION AND EDUCATION

DIVISION OF THE

NATURAL HISTORY SURVEY
STEPHEN A. FORBES. Chwr

Vol. XV] I. BULLETIN Article IV.

The Plankton of Lake Michigan

BY

SAMUEL EDDY

PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS

URBANA, ILLINOIS

November. 1927



STATE OF ILLINOIS

DEPARTMENT OP REGISTRATION AND EDUCATION

A. M. Shelton. Director

BOARD OF

NATURAL RESOURCES AND CONSERVATION

A. M. Sheltox, Chairman

WnxrAjr Tuei.kase. Biology John W. Alvoiid. Engineering

Henry C. Cowles, Forestry Charles M. Thompson, Representing

Edsok S. Bastik. Geology the President of the University oj

Wir.i,iA:\r A. Noyes. Chemistry Illinois

THE NATURAL HISTORY SURVEY DIVISION

Stephen A. Forbes. Chiel

SCHNEPP & BaRN'ES. PrIXTERS
Sprixgfield. III.

1927

734S4—1200



^
Illinois State Xfitural History Survey Bulletin Vol XVTT Art. TV.

k ERRATA "j

Ses 208, 211, 214, 219—for Bacellariaceae read Bacillariaceae,

;e 209, middle of table^for oligactus read oligactis,
I

!e 211, fifth line in table—for Aphanotheca read Aphanothece.
,

;e 213, first line in table—for oligactus read oligactis. A

:e 21.5, fourth line in table—for acuminata Ehr. read acuminatum (Kutz,) CI.

;e 218, sixth paragraph—for Aphanotheca read Aphanothece.

:e 220, fifth paragraph—for acuminata read acuminatum.

e 224, fourth line fi-om bottom—for Pandorin read Pandorina.

Omit last line and read Traverse Bay region.
j

e 228, fifth line from bottom—for Antario read Ontario.



VoLUMK XVII. Article IV.

THE PLANKTON OF LAKP] MICHIGAN

SAMUEL EDDY

Tlie niimite organisms coiistitutiiiij the plankton of the (jreat Lakes
have been stinHed previously more in connection with investigations of

their inter-biotic relations rather than from the primary aspect of the

])lankton. Perhaps the largest amount of work has been done by inves-

tigators who were interested chiefly in the relation of the plankton to the

white-fish industry. This is one of the most important phases of plank-

ton work, because the white-fish as well as other fishes of the Great Lakes
is dependent upon the plankton for food in its early life (Forbes, 1883)—
a fact which has made the study of plankton and plankton production

most valuable. Other investigators have made fragmentary studies of the

plankton of the Great Lakes for taxonomic purposes: Kellicott. Jennings,

and o;hers, for example, devoted their attention to the occurrence of

certain groujis of organisms and to the number and description of species

in those groups as found in the Great Lakes.

The chief purposes of this paper are: (1) to present a general pic-

ture of the plankton of Lake ^lichigan, (2) to determine the relative

abundance of its constituent organisms, and (3) to incorporate and sum-
marize the facts now known relating to the plankton of the Great Lakes.

\'ery little work of a quantitative nature has been published on this

subject within the last twenty years. Previous to this period a number
of qualitative investigations were made on the plankton of Lake Erie. Lake

St. Clair, Lake Michigan, and Lake Superior: and a very important work
of both quantitative and qualitative character was done on Lake Michigan

in the Traverse Bay region by the Michigan Fish Commission (Ward,
18!)6). In the latter investigations, which covered both bottom and plank-

ton organisms, the gross quantity of the plankton was estimated from
silk-net tows, and some idea of the general character of the plankton was
obtained from the relative abundance of the constituent organisms.

Methods and ^L\TERI.\LS

The data for the present paper were oljtained from two series of col-

lections made from Lake Michigan in 1887-1888 and 1!)26-192T. Fifty

silk-net tows (Table I) were made by the Illinois State Laboratory of

Natural History from November, 1887 to November, 1888 from the break-

water at Chicago. Quantitative silk-net and filter-paper collections (Table

II) were made October 16-17, 192G at Indiana State Dunes Park and
Michigan City, Indiana, and near Sawyer, Michigan. Quantitative collec-



204 Illinois Nati-kal Histoisy Sirvey Billetin

tions (Table III) were also made May 14-15, l'J2T at Dunes Park and

Gary, Indiana, and July 10, li)2T at Chicago, Illinois. All of these were

surface tows near the shore, so that the material in this paper relates

only to surface and in-shore conditions. No investigation has been re-

ported on the plankton or the conditions in the central area of the lake.

The material of the older series of collections, which had been ])re-

served in formalin and glycerin, was found to be in excellent condition.

Unfortunately, the accession numbers on some of these collections had be-

come illegible, so that it was imjiossible to secure definite information in

regard to the months of January, February, and March of the year 18.S8.

The collections which were assumed to cover these months showed very

little variation in the constituent organisms from those of the other

months.

Physical Conditions

Lake Michigan offers a very stable habitat for the production of

plankton. Because of its large size and the lack of strong currents, the

physical conditions of the water vary but slightly from year to year

;

therefore, the same constituent organisms may be expected in the plankton

over a long period of time. Forbes (1883) found that the conditions

of life in Lake Michigan were remarkably uniform throughout the sea-

sons and from year to year and that both plant and animal life exhibited

there a regularity and stability in remarkable contrast to their fluctuations

in smaller bodies of water and on the surrounding land. There was little

change, he found, in the relative number of individuals of the various

species or in the absolute number of each. Shelford (Ward and Whipple,

1918) pointed out that Lake Michigan, being a large and deep lake, had

none of the seasonal temperature changes extending to the deeper parts.

Consequently, as only the surface temperature fluctuates, one would ex-

pect the deeper portions to exert a more stabilizing influence on the sur-

face waters than would be found in the waters of more shallow lakes.

The stability of the lake as a biotic factor is strikingly demonstrated by

our comparisons of data covering a period of forty years, for little or no

change has occurred in the composition of the plankton over this long

period. Many of the constituent species, though showing slight seasonal

variations, are rather constantly abundant throughout the year.

The south end of Lake Michigan is composed of gently-sloping sand

beaches exposed to considerable wave action. In the northern portion of

the lake there is some rocky shore line. Areas of mud flats and aquatic

vegetation are rare. All these conditions are characteristic of a primitive

lake. There is little variation in water level or shore line from year to

year, and 'overflow conditions are practically unknown. Cooley (1913)

gives the following figures covering the water level for the years 1860-

1913:
Greatest yearly range of Lake Michigan 1.94 ft.

Least
" " " " '' 59 ft.

Average " " " " " LSI ft.



The Plankton of Lake Mechioan 205

At the south end the sandy character i)f the beaches and the strong
wave action prevent the growth of vegetation with its conse(|uent influ-

ence on the contHlions and Hte of the water. Practically all the plankton,
therefore, must originate within the limnetic area. Shallow breeding
areas such as Kofoid (1!)08) found in the backwaters of Illinois River
are practically unknown. Adventitious species so common in the [)Iank-

ton of the shore and bottom areas of rivers and shallow lakes are rare.

Stable conditions are insured still further by the extremely slow re-

moval and renewal of the water in the lake. Speaking generally. Ward
( Ward and Whipple, 11)18) stated that great dejith in a body of water and
a large inflow in proportion are unfavorable to the abundant production of

plankton, and Ward ( ISDti) computed that there is a change of about one-
eiph'ielh uf (be entire volume of Lake Alichigan in one year. In other

words, there are no extensive outflows to upset the conditions of life in

th.is lake.

The suspended organic matter and silt so common during overflows

in rivers and other plankton-bearing waters—and so detrimental to the

production of jilankton organisms—seem to be at a minimtuii in Lake
Michigan. (The turbidity was not recorded when the collections were
made, but it never seemed to be very high.) All things considered, the

conditions for plankton production in Lake Alichigan apjiroacb those

of the sea as near as do those of any body oi freshwater.

General C'ii.\i<.\ct1':r

The gross bulk of tlie plankton in the water, determined from the

collections made in 1926-1927, is c|uite large. Ward (1896) reported

that the plankton in the upper two meters in the Traverse Bay region

ranged from S.'.) to I 1.12 c. c. per cubic meter, and that the abundance of

the plankton gradually diminished in the lower levels. His data were ob-

tained by allowing the silk-net collections to settle in a graduated cylinder

and computing the volume of the plankton ])er cubic meter. The same
method when used on the recent collections showed an even greater bulk

for the surface plankton. The collections of October, ll)2(i, averaged
1(( c. c, and those of May, 1927, 40 c. c. per cubic meter. Some differ-

ences in bulk may be due to time, locality, and seasonal variations. The
heavy bulk of the May, 1927, plankton may be due to a spring condition,

as Ward's collections were made in summer.

In general, the plankton of Lake Michigan is that which character-

izes large and deep lakes. Its specific character consists principally of

diatoms of the genera AstcrioncUa, StriatcJla I Tabcllaria), and Fragilaria.

Limnetic algae are not very conspicuous. Zooplanktonts are generally

scarce in numbers, but always present to some extent. In the 1887-1888

collections the zooplanktonts, particularly those of the larger sort, were
much more abundant than in the recent collections and sometimes com-
prised nearlv half the total number of organisms present. The absence

of the smaller organisms in the older series makes it reasonable to as-



206 Illinois Natural History Si'RVEy Bulletin'

sume that a coarser net must have been used, which would account for

the loss of many of the smaller organisms and for the relative abundance

of the larger forms.

As quantitative methods were not used in making the 1887-1888 col-

lections, it was impossible to calculate the total volume of plankton at any

time during that period. Qualitatively, however, the older series was
very similar to the recent series.

At all times in the silk-net collections, the phytoplanktonts greatly

outnumbered the zooplanktonts ; the latter, however, made up for their

smallness in numbers by their much larger individual size. Because of

their spines and other peculiarities of shape, the plant species actually oc-

cupied a great deal less space than they seemed to at first glance, or than

their numbers would indicate. Careful measurements, with an ocular

micrometer, of the average actual bulk of the various silk-net organisms

showed that the zooplanktonts, although present in much smaller numbers

than the plant species, often comprised nearly one-half the total bulk.

Considerable variation of this ratio between the animal and plant con-

stituents was shown in different collections, depending on seasonal and

other factors. This ratio would not apply to the total plankton of the

lake, because not enough data were obtained in regard to the smaller

organisms ( nannoplankton ) , some of which escaped through the net but

"were found in the few filter-paper collections.

In all, 119 species were found, most of which were typical plank-

ton species. More data on the nannoplankton would undoubtedly

greatly increase this number. Sixty of these species were phyto-

])lanktcnts and fifty-nine were zooplanktonts. This is only about one-

fifth of the total number of the species listed in the various reports

of previous investigators as r>ccurring in the waters of the Great Lakes.

Of the 66 species occurring in our 1887-1888 collections, 17 (at least

three of which were adventitious) did not occur in our recent collec-

tions ; most of these were never abundant and could have been easily

lost in the later collections. Of the 102 species occurring in our 1926-

1927 collections, 53 were not observed in the earlier collections; these

were either rare or, as previously mentioned, were so small as to escape

through the meshes of the net. Many species of algae which were not

noted in the earlier series showed up in the recent series, though none of

them were abundant. There is no evidence that any of the missing species

did not exist in both periods. Anyone familiar with the methods of

plankton study can easily understand how some of the smaller organisms

by their scanty distribution can easily escape collection and observation.

The 49 species which were common to both periods were usually the larger

and most abundant organisms.

A rich diatom flora predominated in all the collections, the same

species occurring in both periods with few exceptions. Those species

which were most abundant in the recent series appeared in the same pro-

portions in the earlier series.



The PLA^KTo^' of Lake Michigan 207

The same species of copepods (jccurred in both periods with the not-

able exception of Epischura lacustris Forbes, which was abundant in the
early collections but did not appear at all in the recent ones. The same
species of cladocerans were scattered throughout both series. The Pro-
tozoa and Rotifera, never abundant, were limited to a few common species

occurring in most of the collections, and as they are hard to preserve for

identification not enough good deterniinatinns could be made of most of
them to establish their distribution.

Seasonal AsrECT

The data are not extensive enough to justify any definite statement
of seasonal variations in the bulk of the plankton, although the fall col-

lections of 1926 showed only one-fourth the bulk of the spring collec-

tions of 1927. Seasonal variations in constituent species were noticeably
lacking, the dominant diatoms running almost uniformly through the col-

lections of ]8S7-1<SS,S. Astrriomila gracillima, reported as a spring species

in the Illinois River by Kofoid (1908), was abundant throughout the dif-

ferent months, as also were Lysigonium ( Mclosira), Striatclla (Tabcl-
laria). Syncdra. and Fragilaria. Other less abundant diatoms generally

appeared irregularly in the collections. Forbes (l88;i) concluded, from
his own observations and those of B. W. Thomas over a ]»eriod of six-

teen years, that there was little change in the constituent organisms in

Lake Michigan from one season to another, although he noted a sight
increase in number of species in the spring and summer months. In the

1887-1888 collections, the zooplanktonts showed a decided decrease in the

colder months, being almost entirely absent in the collections of Decem-
ber ,'md in those attributed to January. February, and March.

General Distkihution

A fairly uniform distribution of the plankton of Lake Michigan is

to be expected, and very little difference has been noticed in the specific

character of the plankton at different ]>oints. The off-shore waters of

Lake Michigan are fairly well mixed by circulation ; currents sweep south-

ward on the west side, turn at the south end, and flow northward on the

east side (Harrington, 1895), so that the water bearing the plankton at

Chicago is, a few days later, off Michigan City, Indiana.

In all the collections examined, the exact number of organisms was
never the same, and absolute uniformity has never been reported in plank-
ton investigations. A tendency to swarm is indicated by the variations in

abundance in all collections. Reighard (1894) found evidence of plankton
swarming in Lake St. Clair. Forbes (1883) found that the plankton was
not equally distributed throughout the water and was more dense off the
mouths of rivers. These variations, however, were not usually as great

as those between dift'erent habitats or seasons.



208 Il.IJ.NOIS NaTIRAI, HiMTOltY SUHVEY BlLLETIX

Oh

<
a
!s

a
<
>

w

o

3
>-3

3

<1

o o

U '.-4

. £ C8 O s °
CO ZJ

u o u TS
o o u ^
o o o cd

l^rt S !^
; S
. o

« S

" E

OoiooniOnJocScflaSOOt-

a B B B
•2 o o o
cfl o o o 1°

o

00
* C3

d
oi

5 3

to c; 3
>s 3 ii

M S
3

oj -r,

o o<

-5 ci T3 o u

, O ni O O

. -a

oS£oT3g':3oo'a'a
OoS°aioa!OOtCcS CS O

J3

ni ho "

o M as

m i5 2

tiJti;,

sti;

H^6
«S '3

ns ties
^- — ^
ho cS cS

.2'S

d. 2

a

B B

3=3

II
: O

T3

KlXl ^
ci 3 u
e >, m
<! J'-J

o ^ •;

•

(D
>. Z) x:
O CC M I

^ti,3-

-s
3 B "^
«'^S ?>

; 2 .h 5 cs
"=

J .2 .2
*^ 3

't^
"

aj M 3
d ci i. t. O

'

^3 :;: •c a v
J tj) M I' 2 <u

; tS tS 3 3 ^j
3 •„ i, >, >) m
J fa fc M a3<!

j3

B
J3 3
H^
nS .S

3B
3g

A a 3
=" S

"^ 3
iS'S O
3 3 J3000,
> o is
oj o ozoo

N
3

m be

N

• ^ 3

ca

X3 .0 S
m ;3 oj
o
^ (B M
3f^ Z!
^ m M
g >, >,
3 O CJ

OJ o o

° s s

3 3, a
H COM

P» ho 3

a Q 3

CD ^
:-^ S ^
;
u 3 g

3 cii

B " ^
3-S o

t; P. i: t.

ho O M m

.i: -5 3 '-S

WQO&H



The Plankton ok Lake Michigan 209



210 Illinois Natural Histoisy Survey Bi llktix



The Plankton of Lake Michigan 211

o
S

^



212 Illinois N.\tur.\l History Sikvey Bi'llktin

aS 9" .2

S ^ M o

a ^O CD *J 03

rH CO !->

^ ft.2

a
•a
3

o

<
H

Q "

1=1

o oo oo o
o oo oo 10

00000O O T^ O C5
cq LC M irq in

000000o ec o

000000M O T-H

0000
LC o o oW O U3 lO

<o o O O O O
Oi O C5 O O o
(M o o o_ o cq

CD -tj^' 10 ^'"

CO

<0 LO
in t—
t- CO

ti ^ o

.So
0.

cs g 3

,
C3

I J3 >.

QJ M O

s as
S OJ rH

:=; 1-4 2
t- tc u

3 S o

rt O (P^ o -r-

a o ^.
M w ^
o o i^^

>; >>^

000
(M iH

C^ O o>
00 LC O
tH CO O

000000O i-H rH

000000O O rH

i

U cd

° i: j= -s o •-

00 w Q m tiJ o o

M 13 M
C8 01 «
.^ a; 'a
CD u 3J

H CC Ph

T3 ^3



The Planktox of Lake Michigan 213

o o
CD oO 1-t

o o oo o o
in r-H M

o O O ^ ^^ '—

'

o O O "^ '^ ^
C<I (M Tr o ^-H

o oo o
1-t O'

o o o oO O lO o
lO in o

o
O

Be

d

a
CO o QMo

\£, g
•2 ca.a
52 rt w
as .rH p,
OJ Pi OJ

3 ".£:
o bo T3

a " o ts

^ o
3 ^

C 3

3 «•

cd cfi ^-1

•a

s



214 Illinois Natural Hlstory Survey Bult,eti.n

J

^



The Plankton ok Lake Michigan 215

o oo oo o
O <=» 1/3O O 00o o

o o oo o oo o o

o o oo o o
o_ o o
o o cTO lO oO (M O

o oo oo o
o oo o o oo oo o

o o o oo o o oO =; LS O

o o o o o
<^ O c: O OO O :r> C: O

o o t.-: t-t

to ITS C^l M
Tj« -^if C^ M
OO CO Tj^ ^

I. t- _ -

j^ 5 ^' ^

5 5—^

S i2

u c ^ '-r- =i .2 ^

^ S .2
=" c

n a) — ^ =
cs =" x 3 2;

V " ^ -3

; — Q) Bi a= C ~ •"
5 .- ^ aj ^ o ^ ^ w '^^

^ S; C

. > 5 t. p c c ^
1 ,-3 O >. C O >i C

a s -<

M E

S E S n

C3=:

w 3
a> p.

'si
3 E ^ 5

-) « t- CJ

J= =- £- 3 S
c
si

rS M « c
= ? 5 >

-'• CJ — — — -*
>. -S S S n .S
j< C - K K -

fc- "3 !u ^ a; ^
T 3"- ? 'H M -2

•j; X ::; J= J= t.

!. G 3
1 cQ w ;oiffii J3 o c ^c; z

3 5
72 < w 33 X :j cu



216 Illinois Natural Histohy Survey Bulletin

4 t-
- W- IM " M

C^ 9 O

cc th ::: o
« >, m <u

f^
.. ^

=" fe.2

a ^ tc ^

ni •—
- r?

S S

oa

o
O t- >, w <i>

ca

o c o o o c> oO CD <=> O O O C)
<s o o o tra ^ o
w" Iff irt o y5 o o
i-H CO C^ CO i-H i-H o

i-H (ra CO -HO

o o o o o
c> o lo <rj o
CO CO tH (?Q c^

lg-

0.

o oo oO CM

o o oo o o
ITS O O

o o o
i^ o o
US CO li3

o o o
Ci o oO CO (X"

^•s J3
m

Cfi

I ~ M IS

"3 O S fe ^ g
X M

: 3 3

.2 n-r

'^ "S !r!^ a a

o t.

C a 2

^ -,, - „ 3 JJ J3

5f § J3

- H . • O .

CS t- ^ 3

> = Sr
2 S^ S
g ^ CD CS

2 S tt cS .

3 >> 3 3 '

D. O O W)
>> 3 ^ p
OOHP

CD lO O c=> O
CO * ^ ira 05
Ol CO T-H ^ CD

I

i3 C

=3

-:3H

cS cs cd3 S
3 hO^S

2SI
cS

tS

o Z
-a ;-

o o

g, i! MCms

0^ o.=S

cc a, W

_ 0.2
oi .3 3
^ O '-^



The Plankton of Lake Michigan 217

o o o o oo o o ^ o
c: ^D c:_ O o
M 1-H M CO Tl^

o o o -o oo o o o o
CQ CO C<I ITS N

o o oo o o
CO CC M

ifS lC o o ic
-rj* C<3 ur O C^
QC M to d oa

be

J o

a

r, C

o c3 ::j;-^iS t-

• =2 5
K — X 5 2 3
E'^ e 3 'x r- -e

X u: —

oca
. c. 2 £
cd o o
•- >. >,
O o o

c i:
3 O



218 Illinois Natural Hlstohy Survey Bulu;tin

NOTES ON CONSTITUENT ORGANISMS
CYANOPHYCEAE (BLUE-GREEN ALGAE)

The blue-green algae, never very abundant in plankton collections of

Lake Michigan, were represented by a few species which were usually

present in small numbers in most of our collections. Fourteen species

were noted in all. Snow (1902) listed thirty-four species from Lake Erie.

Ward (1896) noted several species from the Traverse Bay region. Whip-
ple ( Leighton, 190T) found three genera of blue-green algae in Lake
Michigan at Chicago.

Merismopedia: Merismopedia fllauca (Ehr.) Nag. appeared in small quan-
tities in the collections of June, 1888. Fragments of the plate-like colonies

occurred in the plankton Oct. 17-18, 1926 at Dunes Park, Michigan City, and
Sawyer, and May 15, 1927 at Dunes Park. The colonies were never very abund-
ant, averaging about 200 per c. m.. although 3,750 per c. m. were counted in

the 1926 collection trom Dunes Park. Snow found this species in Lake Erie.

Ward recorded ill. convoluta Breb. at Traverse Bay.

Coelosphaerium: Coelosphaerium kulzingianum Nag. occurred in small
numbers in the collections of Nov. 1887, Aug. and Sept. 1888, and Oct. 1928.

The colonies reached a count of 90,000 per c. m. at Michigan City, Oct. 17, 1926.

The absence of this species in all the spring collections suggests that it is not

a spring form. Because of its small size and relative scarcity, it appeared to

be of no great importance. Colonies of C nacgclianum Unger were common
(112,000 per c. m.) in the plankton July 10, 1927 at Chicago. Snow recorded

C. Kutzingianuw, Nag. and C. roscum Snow from Lake Erie.

Gomphosphaeria: Colonies of Gomphosphaeria aponina Kutz. occurred only
sparingly (4,000 per c. m.) July 10, 1927 at Chicago. This species was reported

from Lake Erie by Snow.

Aphanocapsa: Floating colonies of Aphanocapsa elacliista W. & G. S. Weit
appeared only in the collections made in the fall of 1926, when they were
quite common. Colonies of much smaller cells, A. delicatissima W. & G. S.

West, occurred at the same time but were never as abundant.

Aphanotheca: Colonies of an undetermined species belonging to this

genus were quite common in the plankton collections in the tall of 1926.

Chroococcus: Three species of Chroococnis occurred in the recent collec-

tions. Probably because of the small size of the colonies, none of this genus
were found in the earlier collections. Colonies of C. dispcrsiis (V. Keiss.)

Lemm. were found occasionally in the 1926-1927 collections. C. minutus (Kutz.)

Nag. and C. limnrticus Lemm. occurred sparingly in the 1926 collections. Snow
reported the latter species and also C. pallidus Ehr. and C. purpureiis Snow from
Lake Erie.

Anabaena: Filaments of a very small undetermined species of Anabaena
occurred sparingly In some of the collections of Dec. 1887, Sept. 1888, Oct.

1888, Oct. 1926, and May 1927. It was never abundant and was probably lost

through the meshes of the net in many of the collections. A. circinalis (Kutz.)

Rab. was common (300,000 per c. m.) in the silk-net collections July 10, 1927

at Cbicago. Snow reported this species from Lake Erie. Ward recorded A.

flos-aquae Kg. from the Traverse Bay region.

Lyngbia: An undetermined species of I^yngbia occurred abundantly in a'l

the 1927 collections. This form was found sparingly in the collections of Oct.

1888. Snow found L. woUei Farlow in Lake Erie.



The Plankton of Lake Mkrkian 219

Oscillatoria: A few strands of Oscillatoria princc/js Vaucher occurred in the
collections of Oct. 1S8S. Snow recorded a number of species from Lalie Erie
but not this same species.

BACELLARIACEAE (DIATOMS)

Diatoms are the most abtindant organisms in the plankton of Lake
Michigan, ru'ery collection contained them in large numbers. Twenty-
six species, chiefly of four genera, were noted in all. Thomas and Chase
(18.SG) collected 215 si)ecies of diatoms during a period of sixteen years
from the water supply of Chicago, many of which undoubtedly were
not plankton diatoms. Thompson (Ward. 18i)(j) found diatoms very
abundant at Traverse Bay and listed fourteen species. Whipple ( Leigh-
ton, 1907) gave eight genera as being common in Lake Michigan at Chi-
cago.

Lysigonium (Melosira): Ly.iifloniiim various Ag. was common in all the
collections examined. L. (iranulata (Ehr.) Raits, occurred occasionally, and a
species of this genus resembling L. arotaria Moore was abundant in the Oc-
tober 1926 collections. Snow reported Melosira arcnaria Moore, M. (jrunulata
(Ehr.) Ralfs., and M. variaiia Ag. from Lake Erie; but neither Whipple nor
Ward reported any species of this genus.

Cyclotella: A species of Cyclotrlhi resembling C. mrncf/hiniana Rabh. was
common (2,500-1,760.000 per c. ra.) in the collections of 1926 and 1927. This
small diatom occurred sparingly in the 18S7-1S88 collections. Snow reported
four species of CyclotcUa. from Lake Erie. Ward listed C. operculata K. from
the Traverse Bay region. Whipple found this genus abundant at Chicago.

Stephanodiscus: Stephanodiscus niagarae Ehr. occurred occasionally in

most of the collections and was abundant in the 1927 collections, reaching a

maximum of 500,000 per c. m. in a filter-paper collection May 14, 1927 at

Dunes Park. Snow found ^'. niagarae in Lake Erie. Ward reported this species
from Traverse Bay, but Whipple listed it as absent from Lake Michigan at
Chicago.

Striatella (Tabellaria) : l<triatrVa fcncstrata (Kutz.) Kuntze was one of

the most abundant organisms in the plankton, reaching a maximum of

143,000,000 per c. m. May 14, 1927 at Dunes Park. Every collection throughout
the year of 1887-1888 was filled with the zigzag chains of this diatom. S.

flocullosa (Roth.) Kuntze was plentiful in most of the collections but never as
abundant as S. fcncstrata. Thompson found both species abundant in the Tra-
verse Bay region. Snow reported them from Lake Erie, and Thomas and Chase
found them in the Chicago water supply. Whipple listed this genus as
abundant in Lake Michigan at Chicago.

Fragilaria: Fragilaria vircscns Ralfs. and f\ croloncnsis (Etiw.) Kitton
were abundant at all times. The ribbon-like strands of these diatoms, together
with StriutcIIa. It^yncdra. and AstcrioncUa. composed most of the plankton. The
most abundant of all the organisms in the plankton was F. crotoncnsis. which
reached a maximum of 384,000,000 iier c. m. in a silk-net collection July 10,

1927 at Chicago. Thompson reported F. capucina Desm. as very common in

Travel se Bay. Snow listed F. crotoncnsis and F. vircsccns from Lake Erie.

Whipple found this genus only occasionally in Lake Michigan at Chicago.
Chase and Thomas reported six species of this genus. Including F. virescens

but not F. crotoncnsis, from the Chicago water supply.



220 Illinois Nati'kal Histouy Survey Billetin

Synedra: Synrdra ulna (Nitzsch.) Ehr. and Syiirdra tcnuissima Elir. were
abundant in all collections. S. ulna, one of the most abundant, reached a maxi-
mum of 176,000,000 per c. m. May 14, 1927 at Dunes Park, while S. tenuinsima.
although never so abundant, reached a maximum of 24,000,000 on the same
date. Both species appeared to flourish more abundantly in the spring and
late fall than in other seasons. Thompson reported 8. ulna and S. afflnis Kutz.
In Traverse Bay, Snow reported S. ulna, and S. oxyrhynchus Kg. from Lake
Erie. Thomas and Chase listed fourteen species of this genus including S.

ulna but not iS. tenuissima from the Chicago water supply.

Asterionella: Astcrionella graclllima (Hantzsch.) Heib., one of the most
common diatoms, occurred in all collections except those of June and July,

188S. Its occurrence throughout the rest of the year suggests that it has a

longer season of growth in Lake Michigan than in other nearby waters, pos-

sibly because of the lower temperatures of Lake Michigan. Kofoid (1908)

reported this species as a spring form In Illinois River with a maximum
abundance of 891,000,000 per c. m. The greatest abundance observed in Lake
Michigan was 100,000,000 May 14, 1927 in a filter-paper collection at Dunes
Park. Thompson reported A. Jormosa Hass. from Traverse Bay. Snow also

listed A. formosa from Lake Erie. Whipple found Astcrionella to be the most
abundant genus at Chicago. Chase and Thomas listed A. jormosa from the

Chicago water supply.

Navicula: Several undetermined species of Navicula occurred very spar-

ingly in the collections of 1927. Diatoms of this genus never appeared in any
quantity in any of the collections. Ward listed three species of Navicula from
Traverse Bay, and Whipple found Navicula to be common at Chicago. Snow
recorded three species from Lake Erie. Forty-nine species of this genus were
listed by Thomas and Chase from the Chicago water supply, but many of them
undoubtedly were not plankton species.

Cocconeisf Cocconeis placentula Ehr, was found rather sparingly May 18S8

at Chicago and May 1927 at Dunes Park. This species reached a maximum
abundance of 100,000 per c. m. in the filter-paper collections. Snow recorded

this species from Lake Erie. Ward found P.. transversalis Greg, in Traverse
Bay. Thompson reported C. placentula as being dredged from the bottom of

Trave-se Bay. Thomas and Cliase listed C. lineata K. and C. pedicuhis Ehr.

from the Chicago water supply.

Gyrosigma (Pleurosigma) : Gyrosigrna acuminata (Kutz.) CI. was found

sparingly at Dunes Park, May 14, 1927, but was not observed in any other

collections. G. attcnuatum Sm. was reported by Snow from Lake Erie but

was not among the six species of this genus listed by Thomas and Chase from
the Chicago water supply.

Amphiprora: Amphiprora ornata Bailey occurred (300,000 per cm.) in

the filter-paper collections May 15, 1927 at Dunes Park and also (48,000) in

the silk-net collections July 10, 1927 at Chicago. A. alata (Ehr.) Kutz. was
found sparingly in the collections made Oct. 17-18, 1926. These species have

not been reported by other workers in any of the Great Lakes except by
Thomas and Chase who reported A. calumetica Thomas and A. ornata from
the Chicago water supply.

Gomphonema: Gomphoncma acuminatum Ehr., which occurred very spar-

ingly in the silk-net collections at Dunes Park May 14, 1927, was quite com-
mon in the 1887-1888 collections except during the months of June, July, and
December. It usually appeared in swarms attached to floating debris. Snow
reported this species and three others from Lake Brie. ' Thomas and Chase
listed eighteen species including G. acuminatum from the Chicago water supply.



The Pi.axktox of Lake Michiiiax 221

Cymbella: CiimhiUn hniccolata lEhr.) Kirchn. occurred sparingly in the
silk-net collections May 14-15, 1927 at Dunes Park but did not appear in any
of the other collections. Snow reported C. miiciilata Kg. and C. rotundrita
H. H. C. from Lake Erie. Thompson found C. gastroUUs to be common in the
Traverse Bay region, Thomas and Chase reported twelve species including
C. Icmceolata from the Chicago water supply,

Encyonema: Encyonema prostratum (Berk,) Kutz, occurred in the tilter-

paper collections (1.400,000 per c, m. May 14, 1927) at Dunes Park. This
species appeared in collections of Nov. 1SS7 and Oct, 1888. apparently having
Thomas and Chase found it and three others of this genus in the Chicago
a fall and spring distribution. Snow reported this species from Lake Erie,
water supply.

Cystopleura: Viistoiilrurn turgiila (Ehr.) Kuntze occurred frequently in

the collections May 14-15, 1927 from Dunes Park. An undetermined species
of this genus also occurred rather sparingly in the same collections. No species
of this genus were observed in any other collections. Snow reported Ci/sto-

plenra (EpitlH-mia) turtiida and three other sjiecies of this genus from Lake
Erie, Thomas and Chase listed six species of this genus including C. turnida
from the Chicago water supply.

Homoeocladia: Ho-mococladia sigmoidea (Nitz. ) Elmore was found spar-
ingly in some of the collections May 14, 1927 from Dunes Park, hut did not ap-
pear in any of the other collections. Snow reported this species as ydzschia
sigmoidea (Nitzsch,) Sm, and another species. .Y, linrari.i Sm., from Lake Erie.
Thompson recorded A', sigmoidea from Traverse Bay, Whipple listed diatoms
belonging to yflzscliia as being very abundant at Chicago. Thomas and Chase
found eleven species of this genus including X. sigmoidea in the Chicago water
supply.

.^,,„. .^„ ^., , . .„ „, , eliptica Sm, and S.

solea Breb, from Lake Erie. Thomas and Chase listed five species of Ciima-
topleura. including C. elipliea but not C. UhriV.s. from the Chicago water supply,

Surirella: tiiiriicUa robusia Ehr. occurred very sparingly (85 per c, m.)
July lu, 1927 at Chicago. Snow recorded three species of this genus but not this

species from Lake Erie, Thomas and Chase listed 10 species of this genus but
not robitsta from Lake Michigan at Chicago,

Campylodiscus: Campi/Iodiseiis hibeniieus Ehr, was found in very small
numbers in one silk-net collection from Dunes Park, May 14, 1927, Snow re-

ported C. cribrosus Sm. from Lake Erie. Thomas and Chase listed (', hihrniieus
and C. norieus Ehr, from the Chicago water supply.

CHLOROPHYCEAE (GREEN ALGAE)

The green algae were never abundant in the plankton of Lake Michi-
gan, Twenty species, some of which were very rare, occurred in the col-

lections, Alany of the smaller species which occurred rarely in the recent

series did not appear in the earlier series ; this may have been due to the

use of a coarser net through which most of the smaller forms were lost.

Snow (1902) recorded liti species from Lake Erie. Thompson (Ward,



222 Illinois Natural History Survey Bulij;tin

18!)6) reported that the green algae were almost entirely absent from the
Traverse Bay region, as he found only a few species there. Whipple
(Leighton, 190?) listed seven genera as common in Lake Michigan at

Chicago.

Closterium: Closteriuvi gracUc Breb., which occurred sparingly in most
of the recent collections, was not observed in any of the 1SS7-1SS8 collections.

C. moniUfrrum (Bory) Ehr. occurred only in the July 1927 collections (80 per
c. m.). Snow noted six species of this genus from Lake Erie but did not include
gracile and monolifcruvi. Whipple reported Closterium as occurring occasion-
ally in Lake Michigan at Chicago.

Spirogyra: Fragments of Spiroc/yra (several unidentified species) were
found occasionally in the 1927 collections and in the collections of April and
June 1888. This genus was not reported by Snow or Thompson, although it was
noted by Whipple as "occasional" at Chicago especially around the water sup-

ply crib.

Cosmarium: An undetermined species of Cosmarium. was found only in

the filter-paper col'eetions May 14, 1927 at Dunes Park (27,000 per c. m.). This
species may have been lost through the meshes in the silk-net collections. Snow
listed eleven species of Cosmarium from Lake Erie.

Chrysophaerella: Some colonies of green algae agreeing with Chrysophae-
rella longispina Lauterborn were quite common in the collections Oct. 17-18,

1926 at Michigan City and Sawyer and July 10, 1927 at Chicago. This species

did not appear in any of the other collections and was not reported from the

Great Lakes by any of the previous investigators.

Dictyosphaerium: Colonies of Dictyosphaerium jmchellum. Wood were quite

common in all of the 1926-1927 collections. The greatest abundance recorded

was 112,000 colonies per c. m. in a silk-net collection July 10, 1927 at Chicago.
This species occurred in small numbers in the collections of August 1888. Snow
reported D. puchellum and D. chrenhergianum Nag. from Lake Erie.

Botryococcus: Colonies of Botryococcus sudetinis Lemm. occurred in

small numbers in the collections of Oct. 17-18, 1926. Snow listed only B. braunii

Kg. from Lake Erie.

Kirchneriella: A few species of Kirchneriella ohcsa Schmidle occurred
sparingly (200 per c. m. ) in the collections Oct. 15, 1926 from Michigan City.

Snow reported this species and K. lunaris (Kirch.) Mob. from Lake Erie.

Oocystis; An undetermined species of Oocystis occurred rarely in the

collections, 200 per c. m. Oct. 18, 1926 at Sawyer and 30,000 per c. m. May 14,

1927 at Dunes Park. Snow reported three species of this genus from Lake Erie.

Sphaerocystis: A few colonies (845 per c. m.) of Sphaerocystis schroetcri

Chodat were found in a silk-net collection May 14, 1927 at Gary and also

(7,000 per c. m.) July 10, 1927 at Chicago. This species has not been reported

for the Great Lakes by any of the other investigators.

Ankistrodesmus: Ankistrodesmus falcatus (Corda.) Raits, was found only

in the collections of May 14-15, 1927 from Dunes Park and July 10, 1927 from
Chicago. Clusters of the crescent-shaped cells were quite abundant (1,350,000

per c. m.) in the filter-paper collections, showing that most of the cells passed

through the silk net. This species was not mentioned by any of the previous

investigators.



Thk Plankton of Lakk Muhigan 223

Coelastrum: Two species of Coelatitruw- were found in several of the col-

lections. ('. rcticulatum (Dangeard.) Senn. was found occasionally In the col-

lections of Oct. 17-18, 1926 and rarely in the collections of Sept. 18S8. C. micro-
porum Nag. was found in two silk-net collections. May 14. 1927 at Gary and
July 10, 1927 at Chicago, and in a filter-paper collection. May 14, 1927 at Dunes
Park. Snow reported four species of this genus, including these two, from Lake
Brie.

Tetrastrum: An undetermined species of Tetrastrum occurred in small
numbers (200 per c. m.) in silk-net collections Oct. 18, 1926 at Sawyer. Species
of this genus were not observed in any of the other collections. This genus
has not been reported from the Great Lakes by any of the previous investigators.

Scenedesmus: Two species of Scenedesmus, which is a very common genus
in small lakes and ponds, were found in the 1926-1927 collections. Because
of their minute size, these species were probalily lost in the earlier collections,

and only a few were retained in the recent collections. M. hijuya (Turpin) Lag.
occurred (8450 per c. m.) May 14, 1927 at Gary and (16,500 per c. m.) in filter-

paper collections of the same date at Dunes Park. ^'. quadricauda (Turpin)
Breb. occurred in rather small numbers (600-33,000 per c. m.) May 14, 1927 at

Gary and Dunes Park and Oct. 18, 1926 at Sawyer. Snow reported ten species
of this genus, including these two species, from Lake Erie. Whipple found this

genus rather abundant at Chicago.

Crucigenia: A very small undetermined species of this genus occurred
(1,000-4,225 per c. m.) in the silk-net collections from Gary and Chicago. This
form did not appear in any of the other collections, nor was it mentioned by any
of the earlier investigators.

Pediastrum: Although Pcdiustrum is quite a common plankton genus, it

was never abundant in our collections. P. bori/anum (Turpin) Menegh. occurred
rarely in the Dec. 1887 and Aug. 18S8 collections and appeared in small numbers
(100-7,000 per c. m.) Oct. 17-18, 1926 and May 14. 1927 at Dunes Park and July
10, 1927 at Chicago. P. simiilcx var. duodcnarium (Bail.) Rab. occurred only
in the silk-net collections Oct, 17, 1926 from Dunes Park and Michigan City. P.

duplex Meyen. was present (40-2,500 per c. m.) in the collections of Oct. 17-18,

1926. Thompson reported only P. bori/anum from Traverse Bay. Snow listed

six species of this genus including these three in Lake Erie. Whipple found
this genus to be common in the Chicago area.

PROTOZOA

Protozoa, because of their .small size and relatively small abundance,
were of little importance in the plankton, even in the warmer seasons when
they were most numerous. The collections contained at least twenty-one
species of protozoans, eleven of which seemed to be typical plankton

forms. The others ]irobably were washed up from the bottom or from
the vegetation growing on piles and floating timbers. Smith (1S!)4)

fotind ten species in the surface ])lankton of Lake St. Clair and a number
of others from the vegetation and bottom. Kofoid (Ward, IS!)!!) report-

ed eighteeti species from the plankton of the Traverse Bay region, but no
littoral species. Jennings (1900) listed twenty-two species as limnetic

in Lake Erie. Whipiile (Leighton, 1907) listed nine genera as present

in the waters of Lake Michigan at Chicago.



224 ILLINOIS Natural History Survey Bi'lij;tix

Centropyxis: Crntroi)yxi!i acuhata Stein occurred sparingly in the July
1888 collections and appeared in small numbers (200 per c, m.) Oct. 17, 1926 at
Sawyer and May 15, 1927 at Dunes Park. This species was never abundant
enough to form an important element of the plankton. Kotoid reported it from
bottom tows in Traverse Bay.

Difflugia: Pour species of Diffliigia were found. D. s/lobosa Duj., the most
abundant of all the rhizopods, reached a maximum of 25,000 per c. m. in the
autumn of 1926 but was rather rare (300 per c. m.) in the spring of 1927.

This species was listed as abundant in Traverse Bay by Kofoid and in Lake
St. Clair by Smith. D. lobes Penard appeared in small numbers in the Sept.
and Oct. collections of 1888. D. corona Wallich occurred only sparingly (150-600
per c. m.) May 14-15 at Dunes Park. Smith found this species in the shallow
waters of Lake St. Clair. D. pi/riformis Perty was found in very small numbers
(200 per c. m.) May 15. 1927 at Dunes Park. Kofoid reported this species as
rare in the plankton of Traverse Bay.

Actinophrys: Actinophrys sol Bhr. appeared in small numbers (200 per
c. m.) May 15, 1927 at Dunes Park. Kofoid reported this species as adventitious
in the plankton of Illinois River. Smith found this species in small numbers
in the surface tows from Lake St. Clair.

Trachelomonas: Trachelomonas hispida Perty was found abundantly
(165,000 per c. m.) in the filter-paper collections May 14, 1927 from Dunes Park.
This species and others of this genus may have been abundant in the plankton
when the older series of collections were made, but because of their size they
probably escaped or were impossible to identify in the preserved material.
Landacre (1908) reported this species from Sandusky Bay.

Euglena: Euglena oxyiiris Schmarda occurred frequently May 14, 1927 at

Dunes Park, reaching a maximum of 275,000 per c. m. in the filter-paper collec-

tions. E. viridis. which was reported by both Jennings and Landacre from Lake
Erie, was not identified in any of the collections examined.

Chlamydomonas: An undetermined species of CtUamydomonas was found
abundantly (330,000 per c. m.) in the filter-paper collections May 14. 1927. This
form did not appear in any of the other collections, probably escaping through
the meshes of the silk net. Snow (1902) listed three species of this genus from
Lake Erie.

Phacus: Phacjis triqueter Ehr. occurred occasionally (16,500 per c. m.) in

the filter-paper collections May 14, 1927. This species was not found in any of

the silk-net collections. In Lake Erie Jennings reported it from East Harbor,

and Landacre listed it from Sandusky Bay.

Cryptomonas: Cryptomonas ovata Ehr. was found in the filter-paper collec-

tions (110,000 per c. m.) May 14, 1927 at Dunes Park. This form was observed
only in fresh living material, and probably because of its minute size it did not
appear in the silk-net collections. Whipple reported this genus as present at

Chicago.

Eudorina: Eudorina elegans Ehr. was found in small numbers (200-1200

per c. m.) in 1926 and 1927. This colonial flagellate has not been reported by
previous investigators from the Great Lakes. Kofoid found the closely related

form Pandorin moriim Bory de. St. Vincent in Traverse Bay.

Uroglena: Colonies of Vroglena americana Calkins occurred occasionally

in two recent collections. Kofoid reported ['. volvox Ehr. as common in the
form Pandorin morum Bory de St. Vincent in Traverse Bay.



TiiK Plankton of Lakf; MumiiAN 225

Dinobryon: DiiKihrijon srrtularia Ehr. was the most abundant protozoan
in the plankton. This species seemed to have a swarming tendency, for it was
found abundantly in some collections only to be almost absent from others of the
same date and place. It was present also in small numbers in the Sept. 1888
collections. In those of Oct. 1926 it reached an abundance of 900,000 per c. m.,

and in the filter-paper collections of May 14, 1927 it reached an abundance of

7.000,000 per c. m. Kofoid found this species to be abundant in the Traverse
Bay region. Smith reported it as abundant in Lake St. Clair, and Whipple
listed it as plentiful in Lake Michigan at Chicago.

Ceratium: Ccrdtiiim hirunrlinrJla Miill. was common in the collections of
Oct. 1926. and occurred in mall numbers in those of Aug. and Sept. 18SS. Kofoid
found this species abundant in the Traverse Bay region, and Smith also found
it numerous in the surface tows of Lake St. Clair.

Peridinium: PcriiUnium tabulatum Ehr. occurred occasionally in the col-

lections of Aug. 18SS but did not appear in any of the others. As this is a
common species in other waters, its apparent scarcity in our collections may be
due to its small size and consequent loss through the meshes of the silk net.

Kofoid found P. tabulntum common in the summer at Traverse Bay, Smith listed

it as scarce in Lake St. Clair, and Jennings recorded it from several parts
of Lake Erie. Whipple listed this genus as fairly common in July at Chicago.

Codonella: Cotlonella crulrra Leidy occurred in small numbers in the col-

lections of July. Aug. and Sept. 1888 and in some of the 1926-1927 collections
reaching a maximum abundance of 32,000 per c. m. in a silk-net collection

July 10, 1927 from Chicago. This small-shelled ciliate was reported by Kofoid
as abundant in the Traverse Bay region. Smith found it abundant in the
plankton of Lake St. Clair and Jennings listed it from Lake Erie.

Vorticella: One or more undetermined species of VorticcUa occurred occa-
sionally in the collections of Sept. and Oct. 1888. They were found in consider-
able numbers (220,000 per c. m.) attached to Hoating debris and diatoms in the
filter-paper collections May 14, 1927 at Dunes Park. Kofoid found Vorticella in

the plankton of the Traverse Bay region. Smith recorded this genus as
abundant on diatoms in Lake St. Clair. Jennings found V. rhabdoatyloidcs Kelli-

cott common in Lake Erie. Whipple listed this genus as common in Lake Michl-
igan at Chicago.

Thuricola: A few specimens of an undetermined species of Thiiricola were
found attached to floating debris in a collection of Sept. ISSS. This form
was adventitious in the plankton, belonging more properly to the shore and bot-

tom. Smith found closely related forms to be scarce among the algae in the
shallow waters of Lake St. Clair.

Podophrya: An undetermined species of this genus occurred attached to

floafing debris in a Sept. ISSS collection. Smith reported P. inicloimm C. & L.

on algae in Lake St. Clair. The same species was found rarely by Kofoid at-

tached to Etiisthiira lacii.itris Forbes in the Traverse Bay region.

Acineta: Several undetermined species of Acineta were found attached to

algae in the collections of Sept. 1888. Jennings reported finding A. mystacina
Ehr. attached to floating material in Lake Erie.

COELENTERATA

Several species of Hydra are the only coelenterates known to occur
in the Great Lakes. Hydra olii/actiis Pallas was found sparingly ( 100

per cm.) in a silk-net collection Oct. 17, 1926 from Michigan City. It



226 Illinois Natural History Sirvev BrLij;Tix

occurred in small numbers in the December 188T and the September 1888

collections. Welch and Loomis ( VJ24} reported the occurrence of Hydra
in great abundance in Lake Erie and in Lake Alichigan near Michigan

City, Indiana.

NEMATHELIMINTHES

Free-living nematodes are predominately bottom forms in Lake
Michigan. A few undetermined nematodes were found in the collections

May 14, 1927 from Dunes Park. These were probably bottom forms

washed up from the shallow waters by wave action.

ROTATORIA

Sixteen species of rotifers were found in the plankton of Lake Mich-

igan, although none of them were ever very abundant. These species

were all typical plankton forms, several of them being distributed through

most of the collections. The rotifers of the Great Lakes as a group have

been thoroughly studied by several investigators. Kellicott ( 18!IG, 1897)

published a long list of the rotifers of Lake Erie in the region of Sandusky

Bay, including both bottom, shore, and limnetic forms. Jennings (1891)

reported twenty-four limnetic species occurring in Lake St. Clair and re-

ferred to the distribution of many species in Lake Erie. In a later and
more complete survey covering most of the rotifers of the United States.

Jennings (1900, 1902) gave a list of twelve species as occurring in the

plankton of Lake Erie and listed seven other species as occurring in the

plankton of others of the Great Lakes. Jennings (Ward 1896) found the

rotifers less abundant in the Traverse Bay region than in Lake St. Clair;

he reported the limnetic forms in the Traverse Bay region to be well

represented and listed fourteen limnetic and eight bottom species.

Synchaeta: Two species of Synchaeta occurred in our collections, S. stylata

Wierzejski on Oct. 17-lS, 1926 and S. trcmula Mull, on May 14-15, 1927. No spe-

cies of this genus were found in the earlier collections; they may have been

present but overlooked, as this genus is sometimes very hard to identify in

ordinarily preserved collections. S. trcmtila was doubtfully reported by Kelli-

cott from a marsh near Lake Erie. Kellicott found S. stylata and S. pi'ctinaia

Ehr. abundantly in Sandusky Bay. Jennings reported S. stylata as present in

Traverse Bay, rare in Lake Erie, and one of the most abundant species in

Lake St. Clair. Whipple listed this genus as present in Lake Michigan at

Chicago.

Polyarthra: Polyarthra trigla Ehr, (P. platyptcra Ehr.) was found in

small numbers in the May, July, and Sept. collections of 1888. This species

also occurred in the collections of Oct. 1926 and May and July 1927, ranging

from 100 to 16,000 per c. m. Jennings found this species abundant in Lake Erie

and reported it for the Traverse Bay region. Whipple listed it as present in

Lake Michigan at Chicago.

Diurella: Small numbers (400 per c. m.) of an undetermined species of

DiurrUa were found Oct. 17, 1926 at Michigan City. Jennings found many
species of this genus in Lake Erie.



The Plankton of Lakk Mi< hi(;an 227

Trichocerca: A few specimens of Trichorrrca ci/liiirlrica (Imhof) (Ratln-

lus ci/lindricd Imhof) occurred in one of tlie September ISSS collections. Jen-

nings fountl many species of this genus including Riitlulus culindriciis Jennings
present in Lake Erie.

Lepadella: [.cixiilrlla ohlonga (Ehr.) (ilctoi>U>ia IrpadcUti Levander) was
found rarely only in the July ISSS collections. This is not a typical limnetic
species but probably a migrant from the bottom. Kellicott reported this

species from Sandusky Bay. Jennings found it in Lake St. Clair and also in

swamps about Lake Erie.

Trichotria: Trichotria trtractis (Ehr.) { Diiiocharis tctractis Ehr.) was
found sparingly in one of the July ISSS collections. This species is probably a
migrant from the bottom, as Jennings listed it from the bottom vegetation of

Lake Erie and Lake St. Clair.

Keratella: KeratcUa (Atiurara ) corhlraris (Gosse) which was found occa-

sionally in the May. July. Aug.. Sept.. and Oct. collections of ISSS was relatively

abundant in all the 1926-1927 collections, reaching a maximum of 17,000 per
c. m. in the filter-paper collections of May 14, 1927 from Dunes Park. K. qunil-

rata (Miill.) (A. aciiUdta Ehr.) was found (oOO-S.4.50 per c. m. ) i:i several of the
1927 collections and more rarely in the July ISSS collections. Jennings found
A', cochlcaris and A', qnadrata abundant in Lake Erie, Lake Michigan, and
Lake St. Clair. A", cochlcaris was reported by Vorce (18S1) from Lake Erie
and by Kellicott from Sandusky Bay. as also was A. fitiiritata Ehr. Jennings
reported A. siirrukitd Ehr. from Lake St. Clair. Whipple listed this genus as
common at Chicago.

Nothoica: Notholca londispina Kellicott was characteristic of most of the
plankton collections, appearing in all except those of Dec. 1887, April 188S, and
May and July 1927. Jennings found it in Lake St. Clair and in Lake Michigan.
N. strliita Miill. (1\. ii< uiniiiata H. & G.) occurred sparingly in our collections of

July 1888 and May and July 1927. Forbes (1883) mentioned this species as
occurring in the plankton of Lake Michigan at Chicago.

Brachionus: Only a single species of this common plankton genus was
found in our collections, a single specimen of Brachionnit capsiiiiflorus Pallas

occurring in an Aug. ISSS collection. Kellicott reported two species of this

genus, but not including this species, from Sandusky Bay. Jetinings found this

species and Brachinous militaris Ehr. abundant in the shallow parts of Lake
Erie.

Schizocerca: A very few (50 per c. m.) specimens of tichizoccrca divcrsi-

cornis Daday were found Oct. 17, 1926 at Alichigan City. This species, which
is more typical of small sha'low lakes, has not been reported from the Great
Lakes by previous investigators.

Asplanchna: Asi)lanchna i;rio(Ioiita Gosse was found occasionally in the

Aug. collections of ISSS. Kellicott found this species abundant and .1. hcrrickii

de Guerne rare in Sandusky Bay. Jennings reported A. priodonta from the
plankton of Lake Michigan and Lake Erie.

Filinia: Filinia (Triarthra) longixcta (Ehr.) occurred sparingly (800 per

c. m.) at Chicago, July 10, 1927. Kellicott found this species abundant in San-
dusky Bay.

Conochiloides: Conochiloidcs doasiiari.s (Hudson) was found in small
numbers in the Aug. ISSS collections. This species was reported from Lake Erie
by Kellicott, but not in any other of the Great Lakes by other workers. The



228 Illinois Natir^vl Hihtouv Survey Billetix

closely related form C. Mppocrcpis (Schrank) (C. volvox Ehr.) has been re-

ported from Lake St. Clair by Jennings and from Lake Erie by Kellicott. An-
other similar form P. unicornis Rousselet was common in tows from Lake Erie
(Jennings) (Kellicott) and from Lake St. Clair (Jennings).

CLADOCERA

Eleven species of cladocerans occurred in our collections. Their rela-

tive abundance was greater in the older series than in the recent series,

undoubtedly because of the type of net used for collecting. Two species,

Daphnia rctrocurva Forbes and Bosmina longispina Leydig, seemed to be

generally typical of the plankton, as they occurred in most of the collec-

tions. Smith (1871) reported two species from Lake Superior. Birge

(Reighard, 1894) found four species in the plankton of Lake St. Clair.

Ward (1896) stated that the Cladocera formed an important element of

the fauna of Lake Michigan in the Traverse Bay region ; he found 25

or 30 species in this region but did not state how many of them belonged

to the plankton. Whipple reported finding only one genus in the plank-

ton of Lake Michigan at Chicago. Nine species of Cladocera were listed

by Birge (1881) from the Chicago Water Supply, nine species by Sars

(1916) from the Georgian Bay region, and twenty-seven species by Bige-

low (1923) from Lake Ontario, Lake Erie, and Georgian Bay.

Sida: Sida crystallina (Miill.) occurred rarely in the Sept. 1888 collections

and also (370 per c. m.) Oct. 17, 1926 at Dunes Park. Forbes found this species

occasionally in Lai e Superior. Birge found it abundant in Lake St. Clair. Sars

and Bigelow both reported it from Georgian Bay. Bigelow found it fairly com-

mon in the shallow parts of Lake Erie,

Diaphanosoma: Diaphanosoma Icuchtenbergiatium Fischer was occasional

in the Sept. 1888 collections, but was common in the Oct. 1S88 collections. Bige-

low found D. brachpiimm (Lieven) fairly common in Georgian Bay and Lake
Erie. He reported that D. Icuchtenhergiamim was not as common in the waters

of Georgian Bay.

Daphnia: Daphnia rctrocurva Forbes occurred in nearly all the collections

except those of 1927, running nearly throughout the year in the 1887-1888 collec-

tions. Because of its large size, it seemed to be quite common (100-300 per c. m.)

D. longispina (Leydig) occurred in small numbers in the collections of Nov.

1887 and July and Sept. 1888 The species of Daphnia reported from the Great

Lakes by the early investigators are rather confused, because of the use of

synonyms and European specific names. Smith reported D. galeata Sars and
D. pcllucida Miill. from Lake Superior. Forbes (1881) reported D. longispina

var. hyallna Leydig from Lake Michigan, and later (1887) he reported D.

retrocurva from Lake Superior. Birge listed D. kahlbergicnsis var. intcxla

Forbes and D. retrocurva from Lake St. Clair. "Whipple reported this genus as

occurring in Lake Michigan at Chicago. Sars found D. rctrocurva in Georgian

Bay. Bigelow reported D. pulex (de Geer), D. rctrocurva. and D. longispina

from Lake Erie and Lake Antario.

Ceriodaphnia: Ceriodaphnia laciistris Birge occurred in small numbers
(100 per c. m.) in the Sawyer collections only. Sars found 0. scitula Forbes in

the plankton of Georgian Bay. Bigelow reported four species of this genus from

Georgian Bay, including C. lacustris as "uncommon."



The Plankton ok Lake Michigan 229

Bosmina: Bosmina longispiiia Leydig. the most abundaut cladoceran oS
Lake Michigan, was one of the conspicuous organisms of the plankton. It was
common in nearly all the collections, being entirely absent only from those of
Dec. ISSS. and reached a maximum of 120,000 per c. m. July 10. 1927 at Chicago.
Birge reported this species as abundant in Lake St. Clair. B. obtu.'iirostris Sars,
which has not been reported previously from the Great Lakes, occurred (100
per c. m.) Oct. 17, 1926 at Dunes Park. B. longirosth.i (Miill. i occurred rarely
from April until Nov. in the ISSS collections. This species was found occa-
sionally by Forbes in the plankton of Lake Superior. Sars and Bigelow both
reported this species from Georgian Bay, and Bigelow also found it in Lake Erie.

Alona: An undetermined species of Alona was found once in a collection
of Aug. ISSS. Forbes reported an undetermined species of this genus from
Lake Superior. Birge found four species of Alona in Lake St. Clair. Bigelow
found .4. affinis (Leydig) abundantly in the plankton from shallow waters of
Georgian Bay.

Chydorus: Chydorus splHnriciis (Miill.) occurred occasionally July ISSS
and rarely Sept. ISSS but was not found in any of the 1926-1927 collections.
Forbes found C. sphaericu.i and C. gihbus Lillj to be common in Lake Superior.
Birge reported C. sphaericiis and C. (ilobosus Baird in Lake St. Clair. Bigelow
found three species of this genus, including C. sphaericus. in Georgian Bay.

Leptodora: Lrptodora kindtii (Focke) occurred occasionally in the collec-

tions of Oct. ISSS and July 1927. This large form was reported by Forbes as
occasional in Lake Superior and in Lake Michigan, by Birge as occasional in

Lake Michigan and in Lake St. Clair, by Sars as common in Georgian Bay, and
by Bigelow as common in Georgian Bay and in Lake Erie.

COPEPODA

Xine species of copepods, all ty])ic:il limnetic tonus, were tot.int!. three

of them occurring in a majority of the collections. Like the cladocerans.

they weie more abundant in the earlier collections than in the recent.

Smith (1.S71) mentioned the occurrence of several species of copepods
in Lake Superior but did not designate the species or indicate their abund-
ance. Forbes (1882) found four species abundant in Lake Michigan, and
in Lake Superior (1887) he found nine species, most of which were com-
mon, (^larsh (189-5) found nine species of copepods in the plankton of
the Traverse Bay region which were the same as those of the other Great
Lakes ; he reported six species from Lake Erie, nine species from Lake
Michigan, and si.xteen species from the plankton of Lake St. Clair.

Epischura: Epischura lacustris Forbes occurred quite abundantly in all

the early collections except those of Dec. 1SS7 and July ISSS. For some un-
known reason this species, which because of its abundance and large size was
very prominent iu the earlier series, did not appear at all in the recent series.

Forbes found this species abundant in Lake Michigan at Chicago and Traverse
Bay and also in Lake Superior. Marsh reported it as common in Lake St. Clair,

Lake Erie, and Lake Michigan.

Diaptomus: Three species of Diaplomiia were found in our collections. D.
minutus Lillj. was common in the collections of Nov.. July. Aug., Sept.. and Oct.

1SS7-1SSS, and in those of 1926-1927. This species was quite conspicuous, rang-
ing in abundance from 300 to 1600 per c. m. D. ashlniidl Marsh was found (200-

2.000 per c. m.) in 1926-1927. Marsh found both species in Lake Michigan and



230 Illinois Natural Histohy Siirvev Btlletix

Lake St. Clair and reported C ?ni)!M/M« as the most common copepod in the Great
Lakes. D. sicilis Forbes occurred occasionally in the June, Aug., and Sept.
collections of 18S8. Forbes found this species abundant in Lake Michigan and
In Lake Superior. Marsh found it common in both Lake Michigan and Lake
St. Clair. Marsh also reported D. oregonensis Lillj. as occurring occasionally in
Lake Michigan and in Lake Erie.

Limnocalanus: Limnocalanus macrurus Sars was found occasionally in the
collections of Sept. 1888. Forbes found this species abundant in Lake Michigan
at Chicago and also in Lake Superior. Marsh reported it from Lake Michigan
and Lake St. Clair.

Cyclops: Three species of Ci/cloi).i occurred in our collections from Lake
Michigan. C. bicuspidatiis Claus was the most abundant, occurring in all the
collections except those of Dec. 1887 and June 1888. This species was reported
by Forbes as abundant in Lake Michigan and Lake Superior. Marsh mentioned
it as the common Cyclops of the Great Lakes occurring in Lake Michigan. Lake
St. Clair, and in Lake Erie. C. prasimis Fischer was abundant in the 1926-1927
collections and was fairly common in all the 1887-1888 collections except those
of Dec, June, and July. Marsh (Ward and Whipple, 1918) stated that this

species was common in the Great Lakes. C. flmbriaius Fischer was found occa-

sionally in the July, Aug., Sept., and Oct. collections of 1888. This species was
not mentioned, at least not under this name, by any of the previous investi-

gators. A total of fourteen species have been reported from the Great Lakes
tjy previous investigators, but many of these are synonyms.

Canthocamptus: An undetermined species of Canthocamptus occurred
(4,225 per c. m.) in the collections of May 14, 1927 from Gary. Forbes found
this genus to be rare in Lake Superior and Lake Michigan.

Summary

The uniformity of the plankton from year to year and from season

to season strikingly demonstrates the stability of Lake Michigan as a

fresh-water habitat. Comparisons of recent collections with those made
forty years ago show that very little change has occurred in the general

composition of the plankton and justify the inference that there have

been no changes in temperature, currents, depth, and chemical composi-

tion of the water sufficient to influence the production of plankton. Of
the species which were abundant in the 1887-1888 collections, only one,

Episeh lira lacustris Forbes, was absent in the recent series. From the

examination of the seasonal collections, there appeared to be a fairly con-

stant and uniform phytoplankton throughout the year, although the zoo-

plankton showed some response to seasonal conditions. Diatoms pre-

dominate at all times and constitute the majority of the organisms of the

plankton, the same species being conspicuous in all the collections ex •

amined.

Acknowledgment

The writer wishes to thank Mr. R. E. Richardson and Mr. H. C.

Oesterling, both of the Illinois State Natural History Survey, for much
valuable criticism and assistance in preparing this paper.



The Pi.ankto-N of Lake Michigan 231

Bibliography
BiGEi,()\v, N. K.

1922. Representative Cladocera of South-Western Ontario. Vniv. Toronto
Biol. Scries 20; 111-125.

BiHGE, E. A.

1S81. Notes on Crustacea iu Chicago water supply. Medical Jour, and
Examiner 14: 5S4-590.

BKIGG.'i. S. A.

1S72. Tlie Diatomaeeae of Lake Michigan. The Lens. CM(;ago. 1: 41.

COOLEY, L. E.

1913. The diversion of the waters of the Great Lakes by way of the
sanitary and ship canal of Chicago. Pub. by The Sanitary District
of Chicago. 216 pp.

Forbes, S. A.

1882. On some Entomostraca of Lake Michigan and adjacent waters. Am.
Xat. 16: 537-542. 640-650.

1883. The iirst food of the common white-fish. Bull. III. istate Lab. Xat.
Hist. 1: 88-99.

1887. On some Lake Superior Entomostraca. Rci)t. U. S. Comm. Fish and
Fisheries. 1SS7. pp. 701-718.

Jennings, H. S.

1894. A list of the Rotatoria of the Great Lakes. Bull. Mieh. Fish Comm.
3. 34 pp.

1900. A report of work on the Protozoa of Lake Erie with especial refer-

ence to the laws of their movements. Bull. V. S. Fish Comm.
19: 105-114.

1900. Rotatoria of the United States with especial reference to those of

the Great Lakes. Bull. V. S. Fish Conhm. 19: 67-104.

1902. Rotatoria of the United States. II. A monograph of the Rattulidae.
Bull. r. S. Fi.<:h Comm-. 22: 275-349.

Kelliiott, D. S.

1S96. The Rotifera of Sandusky Bay. Proc. Am. Micr. Soc. 18: 155-164.

1897. The Rotifera of Sandusky Bay (Second Paper). Proc. Am. ilicr.

HOC. 19: 43-54.

KoFoii). C. A.

1908. The Plankton of the Illinois River, 1S94-1S99. Part II. Constituent
Organisms and their Seasonal Distribution. Bull. III. State Lab.
Xat. Hist. 8. 360 pp.

Landacre, F. L.

190S. The Protozoa of Sandusky Bay and vicinity. Proe. Ohio Acad.
Sci. 4, Part 10.

Leigiiton, M. 0.

1907. Pollution of the Illinois and Mississippi Rivers by Chicago sewage.
V. S. Geol. Surv. Water Supply Paper 194. 369 pp.

Marsh, C. D.

1894. On the Cyclopidae and Calanidae of Lake St. Clair Bull. Mich.
Fish Comm. 5. 24 pp.



232 Illinois Natural Histoky Survey Bulixtin

PlETERS, A. J.

1901. The plants of western Lake Erie. Bull. U. S. Fish Comm. 21: 57-79.

Reighard, J. E.

1S94. A biological examination of Lake St. Clair. Bull. Mich. Fish. Comm.
4. 60 pp.

Sars, G. 0.

1916. Entomostraca of Georgian Bay. In Contr. Canad. Biol. lUll-lSl.'i.

Suppl. 47th Ann. Rept. Dept Marine and Fisheries, Fisheries
Branch, Ottawa, p. 221.

Smith, S. I.

1874. Sketch of the invertebrate fauna of Lake Superior. Repl. V. S.

Fish Comvi. 1872-1873, pp. 690-707.

Snow, J. W.
1902. The plankton algae of Lake Erie with special reference to the

Chlorophyceae. Bull. U. S. Fish Comm. 22: 371-394.

Thomas, B. W. and Chase, H. H.

1887. Diatomaceae of Lake Michigan as collected during the last sixteen
years from the water supply of the City of Chicago. Notar. Ann.
2: 328.

VORCE, C. M.

1880. Some Observations on the minute Forms of Life in the Waters
of the Lakes. Cleveland, 0.

1881. Forms observed in water of Lake Erie. Proc. Am. Micr. Soc. 4th
Ann. Meeting, pp. 50-60.

1882. Microscopical forms observed in the waters of Lake Erie. Proc. Am,.

Micr. Soc. 5th Ann. Meeting, pp. 187-196.

Walton, L. B.

1915. A review of described species of the order Euglenoidina Bloch. Ohio
State Univ. Bull. 19: 343-459.

Ward, H. B.

1896. A biological examination of Lake Michigan in the Traverse Bay
region. Bull. Mich. Fish Comm. 6. 100 pp.

Ward, H. B. and Whipple, G. C.

1918. Fresh water biology. John Wiley and Sons, New York. 1111 pp.

Welch, P. S. and Loomis, H. A.

1924. Hydra oligactis in Douglas Lake, Michigan. Trans. Am. Micr. Soc.

43: 203-235.