OPCE-STR.vp Acta Bot. Croat. 68 (2), 401–419, 2009 CODEN: ABCRA 25 ISSN 0365–0588 Morphotype variations in subfossil diatom species of Aulacoseira in 24 Michigan Lakes, USA KALINA M. MANOYLOV1*, NADJA OGNJANOVA-RUMENOVA2, ROBERT JAN STEVENSON3 1 Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, GA 31061 USA 2 Institute of Geology, Bulgarian Academy of Sciences, Acad. G. Bonchev str. 24, 1113 Sofia, Bulgaria 3 Department of Zoology, Michigan State University, East Lansing, MI 48824 USA Diatom assemblages preserved in lake sediment records can provide proxy data of past environmental changes in biological conditions. In order to investigate past changes in the environment of north-central Michigan, diatom assemblages were studied in sediment cores retrieved from 24 lakes. Diatoms were analyzed from the 'top' and 'bottom' of each core to reconstruct land-use changes in this area. Aulacoseira taxa were identified and evaluated with light and scanning electron microscopy. Results of these observations showed the presence of some variability of the morphological features within North American species populations. Diatom species composition in surface sediments and dif- ferences between tops and bottoms corresponded to changes in land use surrounding the lakes, ranging from predominantly forest and rangeland to urban and agriculturally im- pacted. Diatom-inferred past conditions revealed that the observed morphotypes probably represent taxa with different ecological preferences. The main factors influencing the variability of these morphotypes are changes in the trophic status of the lakes. Key words: diatom, Aulacoseira, ultrastructure, sediment, distribution, morphotype, Michigan lakes Introduction In the last few decades, lakes within large watersheds adjacent to the Great Lakes have been of considerable interest (WOLIN and STOERMER 2005). Information on changes due to human activities is imprinted in the lacustrine sediment composition (STOERMER et al. 1985, FRITZ et al. 1993, BRADBURY et al. 2002) and inferences of past conditions are possi- ble (STOERMER and SMOL 1999). Following changes in diatom assemblages allows the dis- tinguishing of natural disturbances from those caused by the development of the many coastal areas of the Great Lakes (ENACHE and PRAIRIE 2002). ACTA BOT. CROAT. 68 (2), 2009 401 * Corresponding author: kalina.manoylov@gcsu.edu U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:41 Color profile: Disabled Composite 150 lpi at 45 degrees Species within aquatic ecosystems change with the surrounding environment. Algae go through such changes faster than other organisms (BARINOVA et al. 2008) and are consid- ered sensitive indicators of past and current changes. Studies of past environmental condi- tions are limited to inorganic biological remnants such as diatom frustules and other pre- served proxies of past conditions. In sediments, diatoms are abundant and well preserved (STOERMER and SMOL 1999), and diatom species respond sensitively to anthropogenic alterations in land use and cover and resulting changes in nutrient concentration and conductivity (DIXIT et al. 2001). Many reconstructions of lake history based on sub-fossil diatoms have used changes in ratios of centric and pennate diatoms in sediments (e.g. WOLIN and DUTHIE 1999, STONE and FRITZ 2004). Centric diatoms dominate lacustrine sediments (STOERMER and SMOL 1999) and the genus Aulacoseira has been reported in most lakes (ZOHARY 2004, WOLIN and STOERMER 2005). Changes in Aulacoseira species can bring region-specific understanding in freshwa- ter habitats (USOLTSEVA and LIKHOSHWAY 2007). Closely related species have been lumped in many studies because fine level distinctions in taxonomy are too challenging without ex- tensive taxonomic experience. The goals of this study were first to trace coarse changes in centric and pennate diatom species composition between 'top' and 'bottom' sediments and second to compare the domi- nant Aulacoseira species and diatoms were analyzed from the 'top' and 'bottom' of each core. The 'top/bottom' comparison approach has been used in palaeolimnological recon- struction of recent climate change and extensive catchment land-use changes in different locations (DIXIT et al. 1999, MESSERLI et al. 2000, YANG et al. 2002, 2008). Materials and methods Sediment cores were retrieved from 24 lakes in the Muskegon River watershed, Michi- gan (STEVENSON et al. 2007). The Muskegon River watershed drains approximately 2,723 square miles of land and is located in north-central Michigan. The river is approximately 219 miles long from its source at Houghton and Higgins Lakes down to its mouth at Muskegon Lake and, eventually, Lake Michigan. The Muskegon River watershed is one of the largest watersheds in the State of Michigan (http://www.cevl.msu.edu/mrweap/mRiver Map.html). Lakes were sampled at their deepest point, in the deepest basin (GLEW et al. 2001). Glew Corer was used for sediment retrieval. Lake metrics were measured and sum- marized as part of the Muskegon Watershed project. In this study, tops were the surface sediment, bottoms were the deepest intact sediment retrieved by the corer. Using a knife, tops and bottoms were sliced and represented 1cm of sediment (V. LOUGHEED personal communication). Preparation of diatom samples fol- lowed standard methods (BATTARBEE 1986). Diatom relative abundances were determined by subsampling and acid-cleaning a subsample of the sediment algal sample. Subsamples of cleaned diatoms were mounted on microscope slides using NAPHRAX® as mounting medium. A minimum of 600 diatom valves were identified and counted at 1000 times magnification using a Leica DMLB mi- croscope and differential interference contrast optics. Samples were scanned for Aula- coseira species after enumeration of 600 valves. SEM observations were made with acid-cleaned, gold-coated specimens and a scanning electron microscope (SEM, JEOL, Ja- 402 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:41 Color profile: Disabled Composite 150 lpi at 45 degrees pan Electron Optics Laboratories) 6400V with a LaB6 emitter (Noran EDS) at the Center for Advanced Microscopy at Michigan State University. Diatoms were identified primarily with the use of HUSTEDT (1927–1966), KRAMMER and LANGE-BERTALOT (1986, 1988, 1991a, b), PATRICK and REIMER (1966, 1975), as well as more recent or more specific references such as the PIRLA Diatom Iconograph (CAMBURN et al. 1986, KRAMMER 1991a, b, SIVER and KLING 1997, CRAWFORD and LIKHOSHWAY 1998, LIKHOSHWAY and CRAWFORD 2001, HOUK and KLEE 2007) and Diatoms of North America (SIVER et al. 2005). Aulacoseira species have been identified by the following characters: frustule dimen- sions (ranges in valve diameter and pervalvar axis length); areolar rows on the mantle in 10 µm; form and ultrastructure of the areola-type and vola-covered occlusions; form and structure of the linking spines; form and structure of the separation spines; structure of the ringleist – shallow or deep; thick, thin or hollow; number, position and form of the rimoportula; type of the external opening of the rimoportula; other species features – pres- ence of spines; granulae, etc. The following community characteristics were calculated for each sample: richness (to- tal number of taxa observed in a site); Shannon-Weaver diversity index H= –S(i–s)pilog(pi), where pi is the proportion of the total count arising from the i th species (SHANNON and WEAVER 1949); evenness (equitability)=H’/ln(richness) (PIELOU 1969) and Simpson’s dominance index (SIMPSON 1949), which measures the likelihood of two randomly chosen individuals in a sample being the same species. The correlation coefficients (r2) were used to identify relationships between physic- ochemical variables in top and bottom-reference sites. Significant correlations of more than 50% were discussed. All statistical analyses were performed with SYSTAT ® 10 (WILKINSON 1989). Results Lakes varied in depth from Sapphire Lake with 2.2 m to Fremont and Ryerson Lakes with more than 20 m. Total anthropogenic land use varied from less than 4% for 3 lakes to more than 80% in Fremont Lake. Diatom species composition in surface sediments and dif- ferences between tops and bottoms corresponded to the current land use surrounding the lakes, which ranged from predominantly forest (Goose and Long Lakes, Missauke county) and rangeland to urban and agriculturally impacted (Cadillac Lake, Wexford county). Par- ticular combinations of size, depth and human impact conditions allowed the classification of 13 lakes with good conditions, 8 lakes with fair and 3 lakes with poor conditions. For ex- ample, the shallow and eutrophic Brooks Lake with only 23% total land use had the highest cultural eutrophication index and was classified as poor (Tab. 1). We identified 153 diatom species. Centric diatoms were dominant in 55% of the 'top' sediment counts and in 92% of the 'bottom' sediment counts. Aulacoseira species were present in all lakes and dominant in top and bottom counts. No community diversity attrib- utes were significantly different in 'top' and 'bottom' counts. Mean Shannon diversity was close to 1 in both 'top' and 'bottom' counts. Shannon diversity was highest in the 'top' sedi- ment count for Goose Lake (a good quality lake) and the 'bottom' sediment count of Round Lake (a fair quality lake). In the three lakes with poor quality, diversity significantly de- ACTA BOT. CROAT. 68 (2), 2009 403 AULACOSEIRA SPECIES IN SEDIMENTS U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:42 Color profile: Disabled Composite 150 lpi at 45 degrees 404 A C T A B O T .C R O A T .68 (2),2009 M A N O Y L O V K .M .,O G N JA N O V A -R U M E N O V A N .,S T E V E N S O N R .J. Tab. 1. Lake Identity and characteristics. Number abbreviations correspond to numbers in map 1. T_LAND – total land use, where 0% land use means no human alteration or 100 % forest; depth in m; S_CTP – sum of total P in ppb; CEI – Cultural eutrophication; A_OLIGo – Algae as percent oligotrophic taxa ac- cording to Stevenson’s Mid Atlantic trophic index; Lake_IBI – Lake index of biological indicator and Lake condition (Muskegon watershed web). N Lake County T_LAND Depth S_CTP Secchi CEI A_Oligo Lake_IBI Lake Condition 1 Baptist Lake Newaygo 0.53 14.33 14.31 5.77 –0.42 0.06 52.02 Good 2 Brooks Lake Newaygo 0.22 4.13 16.30 0.93 1.03 0.00 8.91 Poor 3 Cadillac Lake Wexford 0.76 3.75 24.60 1.58 0.71 0.01 14.68 Poor 4 Doc and Tom Lake Clare 0.34 6.33 16.59 2.50 0.04 0.04 62.78 Good 5 Fremont Lake Newaygo 0.83 20.67 19.75 3.82 0.62 0.03 29.45 Fair 6 Goose Lake Missauke 0.03 3.50 13.44 1.91 0.06 0.13 72.83 Good 7 Haymarsh Lake Mecosta 0.07 8.67 16.33 3.08 0.05 0.02 36.99 Fair 8 Hess Lake Newaygo 0.42 3.80 13.70 0.60 1.42 0.00 8.47 Poor 9 Hillsview Lake Mecosta 0.13 10.30 14.40 2.00 0.77 0.12 38.01 Fair 10 Horsehead Lake Mecosta 0.34 13.33 14.20 3.50 –0.18 0.04 42.70 Good 11 Little Whitefish Lake Newaygo 0.20 12.00 22.90 3.62 –0.30 0.01 47.24 Good 12 Long Lake C Clare 0.31 17.70 10.10 5.10 –0.50 – 49.35 Good 13 Long Lake M Missauke 0.04 5.00 12.89 2.83 –0.01 0.02 59.65 Good 14 McCoy Lake Osceola 0.61 8.33 33.01 2.58 0.07 0.08 53.75 Good 15 Pickerel Lake Newaygo 0.34 19.25 21.10 4.13 –0.02 0.00 29.29 Fair 16 Rogers Dam Pond Mecosta 0.48 4.40 34.36 1.53 0.64 0.06 33.38 Fair 17 Round Lake Mecosta 0.41 12.50 23.83 2.67 0.40 0.03 33.71 Fair 18 Ryerson Lake Newaygo 0.48 24.17 22.79 5.17 –0.16 0.03 40.80 Good 19 Sapphire Lake Missauke 0.21 2.20 15.00 1.50 –0.11 0.07 57.78 Good 20 School Section Lake Mecosta 0.40 7.00 20.94 3.57 –0.23 0.06 54.82 Good 21 Second Lake Newaygo 0.65 12.33 13.76 3.37 0.26 0.04 36.13 Fair 22 Silver Lake Clare 0.27 14.92 13.76 4.67 –0.34 0.33 64.77 Good 23 Townline Lake Mecosta 0.46 11.43 14.20 2.90 0.32 0.07 43.45 Good 24 Winfield Lake Newaygo 0.64 14.33 33.67 1.95 0.90 0.03 19.67 Fair U : \ A C T A B O T A N I C A \ A c t a - B o t a n 2 - 0 9 \ M a n o y l o v . v p 6 . l i s t o p a d 2 0 0 9 1 2 : 3 8 : 4 2 C o l o r p r o f i l e : D i s a b l e d C o m p o s i t e 1 5 0 l p i a t 4 5 d e g r e e s creased with an increase in human influence 1.01 (± 0.00001 SE 'bottom') to 0.89 (± 0.001 SE 'top'). Baptist Lake had the lowest diversity in both 'top' and 'bottom' counts, so lake quality alone was not a good predictor of diatom sediment diversity. Simpson’s index did not differ between top and bottom (mean 0.74 for both) even though the dominant taxa changed. In 'bottom' sediment samples, taxa observed in counts varied from 21 to 69 taxa (evenness 0.14 to 0.34), while in the 'top' 1 cm sediment species ranged from 17 to 63 dia- tom taxa (evenness 0.06 to 0.34, Tab. 2). A fairly diverse Aulacoseira bottom community reduced to A. subarctica and A. ambigua in the top samples. The main factors influencing the variability of these morphotypes were changes in the trophic status of the lakes (Tab. 3). Aulacoseira taxa from the 'bottom' sediment counts were negatively correlated with depth, cultural eutrophication, and increase in total phosphorus where pennate diatoms dominated the community. In the 'top' diatom community Aulacoseira taxa were positively correlated with depth and oligotrophic conditions (Tab. 4). ACTA BOT. CROAT. 68 (2), 2009 405 AULACOSEIRA SPECIES IN SEDIMENTS Tab. 2. Community attributes in top and bottom sediment sites. SE – standard error; p – significance level. Attributes Bottom Top p mean ±SE min max mean ±SE min max Diversity 1.01 0.045 0.42 1.4 1 0.059 0.19 1.4 ns Richness 46 2.55 21 69 43 2.36 17 63 ns Evennes 0.26 0.009 0.14 0.337 0.26 0.013 0.07 0.341 ns Simpson’s dominance 0.736 0.009 0.663 0.863 0.737 0.013 0.659 0.934 ns Tab. 3. Relative abundance (RA) of Aulacoseira species in top and bottom sediment samples of the 24 Michigan lakes. Taxon RA top, mean (range) RA bottom, mean (range) Aulacoseira ambigua (Grunow) Simonsen 0.22 (0.006–0.54) 0.11 (0.003–0.29) Aulacoseira granulata (Ehrenberg) Simonsen 0.02 (0.002–0.13) 0.02 (0.001–0.08) Aulacoseira granulata morphotype curvata 0,003 Aulacoseira italica (Ehrenberg) Simonsen 0,003 0,003 Aulacoseira nygaardii (Camburn) Camburn et Charles 0,003 Aulacoseira perglabra (Østrup) Haworth 0,08 Aulacoseira pseudoamericana (Camburn) Siver et Kling 0,08 Aulacoseira subarctica (Müller) Haworth 0.19 (0.003–0.52) 0.11 (0.002–0.68) Aulacoseira valida (Grunow) Krammer 0,003 U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:42 Color profile: Disabled Composite 150 lpi at 45 degrees 406 A C T A B O T .C R O A T .68 (2),2009 M A N O Y L O V K .M .,O G N JA N O V A -R U M E N O V A N .,S T E V E N S O N R .J. Tab. 4. Correlations between algal groups and lake dimensions. Percent Aulacoseira in 'top' and 'bottom' samples, other Centric and Pennate diatoms and factors as abbreviated in table 1. DEPTH S_CTP SECCHI CEI A_Oligo LAKE_IBI Au_T Centr-T Pen_T Au_B Centr-B Pen_B DEPTH 1.00 SUMCTPPPB (S_CTP) 0.23 1.00 SECCHI –0.48 0.51 1.00 CULTURALEUT (CEI) 0.11 0.99 0.65 1.00 (A_Oligo) 0.91 –0.18 –0.67 –0.29 1.00 LAKE_IBI 0.57 –0.12 –0.91 –0.29 0.59 1.00 Aulacoseira -top (Au_T) 1.00 0.26 –0.47 0.14 0.90 0.58 1.00 Other centrics-top (Centr-T) 0.42 0.98 0.41 0.95 0.01 –0.04 0.44 1.00 Pennate-top 0.50 –0.56 –0.38 –0.56 0.76 0.06 0.47 –0.39 1.00 Aulacoseira -bottom (Au_B) –0.83 –0.73 0.02 –0.64 –0.54 –0.30 –0.85 –0.85 –0.06 1.00 Other centrics-bottom (Centr-B) 0.33 0.24 0.45 0.35 –0.45 –0.01 0.35 0.04 0.19 0.19 1.00 Pennate-bottom 0.73 0.68 0.24 0.65 0.48 –0.06 0.74 0.80 0.23 –0.92 –0.41 1.00 U : \ A C T A B O T A N I C A \ A c t a - B o t a n 2 - 0 9 \ M a n o y l o v . v p 6 . l i s t o p a d 2 0 0 9 1 2 : 3 8 : 4 2 C o l o r p r o f i l e : D i s a b l e d C o m p o s i t e 1 5 0 l p i a t 4 5 d e g r e e s Aulacoseira species descriptions Aulacoseira ambigua (Grunow) Simonsen (SIMONSEN 1979; Pl. 1, Figs. 1–10) Basionym: Melosira crenulata var. ambigua Grunow (VAN HEURCK, H., 1880–1885) Melosira ambigua (Grunow) O. Müller Aulacoseira ambigua (Grunow) Simonsen (KOBAYASI and NOZAWA 1981: Figs. 1–22) Melosira ambigua (Grunow) O. Müller var. ambigua (CAMBURN and KINGSTON 1986: 20, Pl. I, Figs. 1–5) Aulacoseira ambigua (Grunow) Simonsen (SIVER and KLING 1997: 1808, Figs. 1–12) Aulacoseira ambigua (Grunow) Simonsen (CAMBURN and CHARLES 2000; 13, Pl. 1, Figs. 18–22) Aulacoseira ambigua (Grunow) Simonsen; (SIVER et al. 2005: 33, Pl. 1, Figs. 22, 25–27, Pl. 3, Fig. 3) Valve diameter ranges of 4–14 µm; the height of valve mantle 5.50–14 µm; the areolae on the mantle are in spiral rows 16–20 in 10 µm. The areolae have circular form with deep-seated vela. The linking spines are notched bifid, and terminate each mantle costa. The ringleist is hollow (Pl. 1, Fig. 10). The rimoportulae are two per valve, without stalk. They are located on the ringleist (LIKHOSHWAY and CRAWFORD 2001). Their external open- ings are large, visible in LM (Pl. 2, Fig.5). The separating spines are longer, pointed (LE COHU 1991). Ecology: known from mesotrophic to eutrophic environments, dominant in shallow lakes (VAN DAM et al. 1994, TRIFONOVA and GENKAL 2001, BARINOVA et al. 2008). This taxon disappeared from the top of Cadillac Lake (being with 29% RA) in the bottom sedi- ment, and remained in low abundance in Doc and Tom Lake (both lakes with poor condi- tions). A 15-fold increase from bottom to top was observed in Fremont Lake. This taxon was not observed in any lake classified as 'Good' (Tab. 1). Aulacoseira granulata (Ehrenberg) Simonsen (SIMONSEN 1979; Pl. 2, Figs. 1–6) Basionym: Gallionella granulata Ehrenberg 1841 Melosira granulata (Ehrenberg.) Ralfs (PRITCHARD 1861: 820) Melosira granulata (Ehrenberg.) Ralfs (STOERMER et al. 1981: 348, Pl. 2, Figs. 21–33) Aulacoseira granulata (Ehrenberg) Simonsen (SIVER and KLING 1997: 1813, Figs. 23–28) Valve diameter ranges of 3–11.50 µm; the height of valve mantle 10–17 µm; the areolae on the mantle are in straight or spiral rows 10–15 in 10 µm. The areolae are coarse, round to square, covered with velar complex (CRAWFORD and LIKHOSHWAY 1998). The velar plate occurs on the outside. The linking spines are notched triangular. The rimoportulae are found on the valve face/mantle junction, near the ringleist (Pl. 1, Fig. 5). The external open- ing is large, visible in LM (LIKHOSHWAY and CRAWFORD 2001). Internally, the rimoportula has tightly curved stalks lying close to the mantle surface (LIKHOSHWAY and CRAWFORD 2001). The separating spines are conical with varying length, from short to almost the length of the valve mantle. Ecology: known from mesotrophic to highly eutrophic environments, dominant in shal- low lakes (VAN DAM et al. 1994, SIVER and KLING 1997, TRIFONOVA and GENKAL 2001, BARINOVA et al. 2008). ACTA BOT. CROAT. 68 (2), 2009 407 AULACOSEIRA SPECIES IN SEDIMENTS U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:30 Color profile: Disabled Composite 150 lpi at 45 degrees 408 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. Pl. 1. Aulacoseira ambigua (Grun.) Simonsen Fig. 1 – girdle view – LM, Round Lake, top sedi- ments; Figs. 2, 3 – girdle view with cross-section focus – LM, Silver Lake, bottom sediments; Figs. 4 a, b – girdle view with cross-section focus – LM, Cadillac Lake, top sediments; Fig. 5 – sibling valves, showing spiral rows of areolae with external openings of the rimoportulae, SEM, Round Lake, top sediments; Figs. 6, 7 – sibling valves, SEM, Cadillac Lake, top sedi- ments; Fig. 8 – detail of linking spines – triangular with bicuspid ends, SEM, Cadillac Lake, top sediments; Fig. 9 – sibling valves with dissolution, see the prominent form of the linking spines – the ends are clavate, SEM, McCoy Lake, bottom sediments; Fig. 10 – inner surface of the girdle, the Ringleist is hollow, SEM, Cadillac Lake, top sediments. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:32 Color profile: Disabled Composite 150 lpi at 45 degrees ACTA BOT. CROAT. 68 (2), 2009 409 AULACOSEIRA SPECIES IN SEDIMENTS Pl. 2. Aulacoseira granulata (Ehrenber) Simonsen. Fig. 1 – girdle view – LM, Ryerson Lake, top sediments; Fig. 2 – girdle view – LM, Second Lake, top sediments; Figs. 3a, b – girdle view with cross-section focus – LM, Ryerson Lake, bottom sediments; Fig. 4 – girdle view – LM, Haymarsh Lake, bottom sediments; Fig. 5 – Aulacoseira ambigua (above) and A. granulata (below) with long pointed separating spines, SEM, Cadillac Lake, top sediments; Fig. 6 – A. granulata, external opening of the rimoportula arrowed, SEM, Cadillac Lake, top sediments; Fig. 7 – A. italica (Ehrenberg) Simonsen, LM, Horsehead Lake, top sediments; Figs. 8 a, b – A. nygaardii (Camburn) Camburn and Charles, girdle view with cross section focus, LM, Mc- Coy Lake, bottom sediments; Fig. 9 – A. nygaardii (Camburn) Camburn and Charles, sibling valves with T-shaped tips of the spines, SEM, McCoy Lake, bottom sediments. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:33 Color profile: Disabled Composite 150 lpi at 45 degrees Aulacoseira granulata mophotype curvata (Hustedt) Krammer Basionym: Melosira granulata var. curvata Grunow (VAN HEURCK, H., 1880–1885) Aulacoseira granulata mophotype curvata (Hustedt) Krammer (KRAMMER 1991a: Figs. 6–8, 19) Valve diameter ranges 5–7.50 µm; the height of valve mantle 12.50–16.50 µm; the areolae on the mantle are in straight or spiral rows 12 in 10 µm. Ecology: known from mesotrophic to eutrophic environments as A. granulata (VAN DAM et al. 1994) typical of shallow lakes (TRIFONOVA and GENKAL 2001). In Muskegon lakes we found it in Townline Lake, which has good conditions. Aulacoseira italica (Ehrenberg) Simonsen (SIMONSEN 1979; Pl. 2, Fig. 7) Basionym: Gallionella italica Ehrenberg 1838 Melosira italica (Ehrenberg) Kützing (KÜTZING 1884: 55, Pl. 2, Fig. 4) Aulacoseira italica (Ehrenberg) Simonsen (KOBAYASI and NOZAWA 1981: Figs. 1–11) Aulacoseira italica (Ehrenberg) Simonsen (KRAMER 1991b: Fig. 44) Aulacoseira italica (Ehrenberg) Simonsen emend. Crawford, Likhoshway et Jahn (CRAWFORD et al. 2003: 17, Figs. 2–14) Valve diameter ranges of 8–11 µm; the height of valve mantle 9–14 µm; the areolae on the mantle are in straight or sinistrorse spiral rows 16–18 in 10 µm. The areolae are subcircular, or, more usually, elongated to fine slits (CRAWFORD et al. 2003). The velum, a spongiform plate, occurs on the inner aperture. The rimoportulae are usually two per valve and positioned 4–5 areolae distant from the ringleist. Ringleist is solid, narrow and shallow (CRAWFORD et al. 2003). The linking spines are large and T-shaped. The separation spines are the same length as linking spines, but are pointed and are rarely found on each valve. Ecology: Known from mesotrophic to eutrophic environments, dominant in shallow lakes (VAN DAM et al. 1994, TRIFONOVA and GENKAL 2001). Aulacoseira nygaardii (Camburn) Camburn et Charles (CAMBURN and CHARLES 2000; Pl. 2, Figs. 8–9) Basionym: Melosira nygaardii Camburn 1986 Aulacoseira nygaardii (Camburn) Camburn et Charles (CAMBURN and CHARLES 2000: 14, Pl. 3, Figs. 9, 16–22) Aulacoseira nygaardii (Camburn) Camburn et Charles (SIVER and HAMILTON 2005: 258, Figs. 1–16) Aulacoseira nygaardii (Camburn) Camburn et Charles (SIVER et al. 2005: 35, Pl. 1, Figs. 11–16, Pl. 2, Figs. 6–8) Valve diameter 10 µm; the height of valve mantle 6 µm; the areolae on the mantle are in straight rows 22 in 10 µm. The areolae are circular to rectangular; the position of the velum (type 'rotae’) is attached down into the base of areola (SIVER and HAMILTON 2005). The ringleist is very shallow. The linking spines are short, with equal length and T-shaped end- ings. Ecology: known from acidic, nutrient-poor waters (SIVER and HAMILTON 2005, SIVER et al. 2005) this taxon was rare in our study and appeared in the 'bottom' sediment of McCoy Lake. 410 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:33 Color profile: Disabled Composite 150 lpi at 45 degrees ACTA BOT. CROAT. 68 (2), 2009 411 AULACOSEIRA SPECIES IN SEDIMENTS Pl. 3. Aulacoseira perglabra (Østrup) Haworth. Fig. 1 – valve view, LM, McCoy Lake, bottom sed- iments; Figs. 2, 3, 4, 5 – girdle view – LM, McCoy Lake, bottom sediments; Fig. 6 – girdle view, see the long and narrow linking spines, SEM, McCoy Lake, bottom sediments; Fig. 7 – valve view with peripheral ring of elongated areolae, the second (inner) ring is partial with smaller and cruciate areolae with vela, SEM, McCoy Lake, bottom sediments; Fig. 8 – valve view with more regular second peripheral areolar ring, SEM, McCoy Lake, bottom sediments; Fig. 9 – The velum of the areola, SEM, McCoy Lake, bottom sediments. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:35 Color profile: Disabled Composite 150 lpi at 45 degrees Aulacoseira perglabra (Østrup) Haworth (HAWORTH 1988; Pl. 3, Figs. 1–9) Basionym: Melosira perglabra Østrup 1910 Melosira perglabra Østrup (CAMBURN and KINGSTON 1986: 28, Pl. 4, Figs. 59–65, Pl. 5, Figs. 77–78) Aulacoseira perglabra (Østrup) Haworth (SIVER and KLING 1997: 1818, Figs. 48–53, 60–63) Aulacoseira perglabra (Østrup) Haworth (CAMBURN and CHARLES 2000: 14, Pl. 4, Figs. 1–8) Aulacoseira perglabra (Østrup) Haworth (SIVER et al. 2005: 1, Figs. 7–10, 23–24: 2, Figs. 3–5) Valve diameter ranges 5.50–13.50 µm; the height of valve mantle 1.50–4.00 µm; the areolae on the mantle are in very short rows (12–21 in 10 µm) and are normally obscured by the overlapping spines of the sibling valve. The areolae are covered by vela. The rimo- portula is single, small, and sits in a narrow band as in LIKHOSHWAY and CRAWFORD (2001). There is a lack of any noticeable ringleist (SIVER and KLING 1997). The linking spines are long and narrow, with flat ending as shown in CRAWFORD and LIKHOSHWAY (1998, Fig. 11). They are carried on buttresses spanning the margin of the face and mantle. On the valve face there is one peripheral ring of elongated areolae that extends onto the mantle, but sometimes smaller crucial areolae form second (inner) partial ring. Ecology: known from oligotrophic conditions (SIVER and KLING 1997, TRIFONOVA and GENKAL 2001) this taxon was not observed in 'top' sediment samples. We found it in 'bot- tom' sediments of McCoy Lake. Aulacoseira pseudoamericana (Camburn) Siver et Kling (SIVER and KLING 1997; Pl. 4, Figs. 1–9) Basionym: Melosira pseudoamericana Camburn 1986 Valve diameter ranges 8.50–13.00 µm; the height of valve mantle 3.00–6.00 µm; the mantle is unornamented. The valve face is ornamented with two, sometimes three, periph- eral rings of small and irregularly arranged areolae. The single rimoportula is positioned near the junction of the valve face and mantle (SIVER and KLING 1997). The ringleist is very shallow. The linking spines are spatulate with apiculate tips (Pl. 4, Fig. 5), or long and nar- row – similar to Aulacoseira perglabra (Østrup) Haworth (Pl. 3, Fig. 6). Ecology: this taxon was rare and appeared in bottom sediments of McCoy Lake, where trophic conditions are good. Previously this taxon was reported together with A. perglabra in oligotrophic environments (SIVER and KLING 1997). Aulacoseira subarctica (O. Müller) Haworth (HAWORTH 1988; Pl. 5, Figs. 1–11) Basionym: Melosira italica ssp. subarctica O. Müller 1906 Melosira italica ssp. subarctica O. Müller (CAMBURN and KINGSTON 1986: 24, Pl. 2, Figs. 34–35, 37–40) Aulacoseira subarctica (O. Müller) Haworth (SIVER and KLING 1997: 1811, Figs. 13–22) Aulacoseira subarctica (O. Müller) Haworth (CAMBURN and CHARLES 2000: 15, Pl. 4, Figs. 23–31) 412 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 9. listopad 2009 13:41:35 Color profile: Disabled Composite 150 lpi at 45 degrees ACTA BOT. CROAT. 68 (2), 2009 413 AULACOSEIRA SPECIES IN SEDIMENTS Pl. 4. Aulacoseira pseudoamericana (Camburn) Siver et Kling. Figs. 1–4 – girdle view – LM, Mc- Coy Lake, bottom sediments; Figs. 5, 6 – sibling valves, unornamented mantle and spatulate spines with apiculate tips, SEM, McCoy Lake, bottom sediments; Fig. 7 – valve view with pe- ripheral, irregularly arranged areolae, SEM, McCoy Lake, bottom sediments; Fig. 8 – valve inside view with internal projections of the rimoportulae, very shallow ringleist, SEM, Mc- Coy Lake, bottom sediments; Fig. 9 – valve inside view, detail with the peripheral rings of areolae, SEM, McCoy Lake, bottom sediments. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:49 Color profile: Disabled Composite 150 lpi at 45 degrees 414 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. Pl. 5. Aulacoseira subarctica (O. Müller) Haworth. Fig. 1 – girdle view – LM, Second Lake, top sediments; Figs. 2, 3, 4 – girdle view – LM, Ryerson Lake, top sediments; Fig. 3 – girdle view – LM, Ryerson Lake, bottom sediments; Fig. 5 – girdle view – LM, Hillsview Lake, bottom sediments; Fig. 6 – valves of A. ambigua and A. subarctica – on the valve face of A. subarctica there are a few areolae, located close to the margin, SEM, Pickerel Lake, bottom sediments; Fig. 7 – sibling valves with clearly overlapping cingulae, SEM, Pickerel Lake, bottom sediments; Figs. 8, 9, 10 – girdle view, the isomorphic spines are of equal length; see, arrowed, the external opening of the rimoportula (with curved stalk), located near the well developed ringleist, SEM, Pickerel Lake, bottom sediments; Fig. 11 – girdle view – a long narrow valve, left – ligula shaped cingulum, SEM, Ryerson Lake, top sediments. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:51 Color profile: Disabled Composite 150 lpi at 45 degrees Valve diameter ranges 4–22.5 µm; the height of valve mantle 6–15 µm; the areolae on the mantle (14–25 in 10 µm) are in spiral pervalvar rows. The areolae are small with deep-set vela (CRAWFORD and LIKHOSHWAY 1998). The rimoportulae are two per valve, without stalk. They are found near the ringleist (Fig. 9) and their external openings are large and visible in LM (LIKHOSHWAY and CRAWFORD 2001). The ringleist is well developed. To our knowledge only isomorphic spines have been described for this taxon (GIBSON et al. 2003, WOLFE and EDLUND 2005). All spines are pointed and of equal length. Ecology: similarly to literature findings of abundance in oligotrophic conditions (VAN DAM et al. 1994, SIVER and KLING 1997, TRIFONOVA and GENKAL 2001, TUJI and HOUKI 2004, BARINOVA et al. 2008), this taxon was abundant in both top and bottom sediment in lakes of good and fair trophic conditions, but appeared only in the bottom sediment of Brooks and Hess Lakes, classified as lakes with poor conditions. Aulacoseira valida (Grunow) Krammer 1991 Basionym: Melosira crenulata var. valida Grunow (VAN HEURCK 1880–1885) Melosira italica var. valida (Grunow) Hustedt 1927 Melosira italica var. valida (Grunow) Hustedt (CAMBURN and KINGSTON 1986: 25, Pl. 2, Fig. 36) Aulacoseira valida (Grunow) Krammer (KRAMMER 1991b: Figs. 23–29, 31, 36–39) Aulacoseira valida (Grunow) Krammer specimens conspecific with Aulacoseira ita- lica (Ehrenberg) Simonsen (SIVER and KLING 1997: 1815, Figs. 42–45) Aulacoseira valida (Grunow) Krammer (CAMBURN and CHARLES 2000: 15, Pl. 5, Figs. 1–4). Aulacoseira valida (Grunow) Krammer (SIVER et al. 2005: 40, Pl. 3, Figs. 1–2). Valve diameter 8 µm; the height of valve mantle 10 µm; the areolae on the mantle are 12 in 10 µm, formed dextrorse spirals. Areolae become enlarged longitudinally towards the valve mantle (HOUK and KLEE 2007). The rimoportula is located in the inner side of the ringleist (LIKHOSHWAY and CRAWFORD 2001). The linking spines are long, relatively thick, with T-shaped enlarged distal edge. Ecology: This taxon, reported from neutral to mesotrophic conditions (SIVER et al. 2005) was rare and appeared in bottom sediments of McCoy Lake. Discussion Within diatom communities from Michigan lake sediment cores we saw a 44% de- crease in Aulacoseira species diversity from bottom to top sediment layers. No other dia- tom group, such as centric diatoms or pennate diatoms, experienced such a decrease. Dia- tom species composition between tops and bottoms corresponded to the current land use surrounding the lakes, which ranged from predominantly forest and rangeland to urban and agriculturally impacted. Inferred past conditions revealed that the observed morphotypes probably represent taxa with different ecological preferences. 'Bottom' Aulacoseiras like A. granulata and A. italica did not change with human influence, while A. subarctica and A. ambigua increased in abundance. Aulacoseira granulata morphotype curvata, A. nyga- ardii, A. perglabra and A. pseudoamericana were absent in the 'top' sediment and were re- placed with A. ambigua and A. subarctica. The main factors influencing the variability of these morphotypes were changes in the trophic status of the lakes. ACTA BOT. CROAT. 68 (2), 2009 415 AULACOSEIRA SPECIES IN SEDIMENTS U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:51 Color profile: Disabled Composite 150 lpi at 45 degrees Diatom-inferred indices for changes in lake water levels and trophic status have been based on species presence or absence (WOLIN 1996). In this study we linked Aulacoseira species with the trophic status of lakes in Michigan, where good quality lakes are abundant. Species such as A. nygaardii, A. perglabra and A. pseudoamericana that occurred fre- quently in bottom sediments were absent in the top sediment and were replaced predomi- nantly with A. ambigua. In poor quality lakes, A. subarctica disappeared in the top sedi- ment. We concentrated on centric diatoms and Aulcoseira, but changes in pennate diatoms remain unclear. Acknowledgement We are very grateful to the field crew led by V. Lougheed for collecting the samples. The authors are grateful to two anonymous reviewers for constructive suggestions that im- proved the manuscript significantly. This research was supported by a grant to Dr. R. J. Stevenson from the Great Lakes Fisheries Trust. References BARINOVA, S. S., MEDVEDEVA, L. A., ANISIMOVA, O. V., 2008: Diversity of algal indicators in environmental assessment (in Russian). Pilies Studio, Jerusalem, Israel. BATTARBEE, R. W., 1986: Diatom analysis. In: BERGLUND, B. E. (ed.), Handbook of Holo- cene palaeoecology and palaeohydrology, 527–570. John Wiley and Sons, Chichester. BRADBURY, P., CUMMING, B., LAIRD, K., 2002: A 1500-year record of climatic and environ- mental change in Elk Lake, Minnesota, 3: Measures of past primary productivity. Jour- nal of Paleolimnology 27, 321–340. CAMBURN, K. E., KINGSTON, J. C., 1986: The genus Melosira from soft-water lakes with special reference to northern Michigan, Wisconsin and Minnesota. In: SMOL, J. P., BATTARBEE, R. W., DAVIS, R. B., MERILÄINEN, J. (eds), Diatoms and lake acidity, 17–34. Dr. W. Junk Publishers, Dordrecht. CAMBURN, K. E., KINGSTON, J. C., CHARLES, D. F. (eds.), 1986: PIRLA Diatom Iconograph. Contains 53 photographic plates and 1059 figures, plus figure legends. Report Number 3. Indiana University, PIRLA Unpublished Report Series, Bloomington, IN. CAMBURN, K. E., CHARLES, D. F., 2000: Diatoms of low alkalinity lakes in the northeastern United States. Special Publication 18, The Academy of Natural Sciences of Philadel- phia, Philadelphia. CRAWFORD, R. M., LIKHOSHWAY, Y. V., 1998: The velum of species of the diatom genus Aulacoseira Thwaites. Proceedings 15 International Diatom Symposium, Liechten- stein, 275–287. CRAWFORD, R. M., LIKHOSHWAY, Y. V., JAHN, R., 2003: Morphology and identity of Aulacoseira italica and typification of Aulacoseira (Bacillariophyta). Diatom Research 18, 1–19. DIXIT, S. S., SMOL, J. P., CHARLES, D. F., HUGHES, R. M., PAULSEN, S. G., COLLINS, G. B., 1999: Assessing water quality changes in the lakes of the northeastern United States us- ing sediment diatoms. Canadian Journal of Earth Sciences 56, 131–152. 416 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:51 Color profile: Disabled Composite 150 lpi at 45 degrees DIXIT, S. S., KELLER, W., DIXIT, A. S., SMOL, J. P., 2001: Diatom-inferred dissolved organic carbon reconstructions provide assessments of past UV-B penetration in Canadian Shield lakes. Canadian Journal of Fisheries and Aquatic Sciences 58, 543–550. ENACHE, M., PRAIRIE, Y. T., 2002: WA-PLS diatom-based pH, TP and DOC inference mod- els from 42 lakes in the Abitibi clay belt area (Quebec, Canada). Journal of Paleo- limnology 27, 151–171. FRITZ, S. C., JUGGINS S., BATTARBEE R. W., 1993: Diatom assemblages and ionic character- ization of lakes of the northern great-plains, North-America – a tool for reconstructing past salinity and climate fluctuations. Canadian Journal of Fisheries and Aquatic Sci- ences 50, 1844–1856. GIBSON, C. E., ANDERSON N. J., HAWORTH E. Y., 2003: Aulacoseira subarctica: taxonomy, physiology, ecology and palaeoecology. European Journal of Phycology 38, 83–101. GLEW, J. R., SMOL, J. P., LAST, W. M., 2001: Sediment core collection and extrusion. In: LAST, W. M. and J. P. SMOL (eds), Tracking environmental change using lake sediments, 1: Basin analysis, coring, and chronological techniques, 73–105. Kluwer Academic Publishers, Dordrecht. HAWORTH, E. Y., 1988: Distribution of diatom taxa of the old genus Melosira (now mainly Aulacoseira) in Cumbrian waters. In Round, E.F. (ed.), Algae and the aquatic environ- ment, 138–167. Biopress Ltd, Bristol. HOUK, V., KLEE, R., 2007: Atlas of freshwater centric diatoms with a brief key and descrip- tion 2. Melosiraceae and Aulacoseiraceae (Supplement to Part 1). Fottea 7, 85–255. HUSTEDT, F., 1927–1966: Die Kieselalgen Deutschlands, Österreichs und der Schweiz mit Berücksichtigung der übrigen Länder Europas sowie der angrenzenden Meeresgebiete. In Dr. L. Rabenhorst’s Kryptogramen-Flora von Deutschland, Österreich und der Schweiz, 7. Akademische Verlagsgesellschaft, Leipzig, Germany. KOBAYASI, H., NOZAWA, M., 1981: Fine structure of fresh water centric diatom Aulacoseira ambigua (Grunow) Simonsen. Japanese Journal of Phycology 29, 121–128. KRAMMER, K., 1991a: Morphology and taxonomy in some taxa of the genus Aulacoseira Thwaites (Bacillariophyceae). 1. Aulacoseira distans and similar taxa. Nova Hedwigia 52, 89–112. KRAMMER, K. 1991b: Morphology and taxonomy in some taxa of the genus Aulacoseira Thwaites (Bacillariophyceae), 2. Taxa in the A. granulata- italica- and lirata-groups. Nova Hedwigia 53, 477–496. KRAMMER, K., LANGE-BERTALOT, H., 1986: Bacillariophyceae, 1: Naviculaceae. In ETTL, H., GÄRTNER, G., GERLOFF, J., HEYNIG, H. MOLLENHAUER, D. (eds.), Süsswasserflora von Mitteleuropa 2, 1–876. Gustav Fisher Verlag, Jena. KRAMMER, K., LANGE-BERTALOT, H., 1988: Bacillariophyceae, 2: Bacillariaceae, Epithe- miaceae, Surirellaceae. In ETTL, H., GÄRTNER, G., GERLOFF, J., HEYNIG, H. MOLLEN- HAUER, D. (eds.), Süsswasserflora von Mitteleuropa 2, 1–596. Gustav Fisher Verlag, Stuttgart. KRAMMER, K., LANGE-BERTALOT, H., 1991a: Bacillariophyceae, 4: Achnanthaceae. Kri- tische Ergänzungen zu Navicula (Lineolatae) und Gomphonema. In: ETTL, H., GÄRTNER, G., GERLOFF, J., HEYNIG, H. MOLLENHAUER, D. (eds.), Süsswasserflora von Mittel- europa 2, 1–437. Gustav Fisher Verlag, Stuttgart. ACTA BOT. CROAT. 68 (2), 2009 417 AULACOSEIRA SPECIES IN SEDIMENTS U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:51 Color profile: Disabled Composite 150 lpi at 45 degrees KRAMMER, K., LANGE-BERTALOT, H., 1991b: Bacillariophyceae, 3: Centrales, Fragila- riaceae, Eunotiaceae. In: ETTL, H., GÄRTNER, G., GERLOFF, J., HEYNIG, H. MOLLEN- HAUER, D. (eds.), Süsswasserflora von Mitteleuropa, 2/3, 1–576. Fischer, Stuttgart. KÜTZING, F. T., 1844: Die kieselschaligen Bacillarien oder Diatomeen. Förstermann, Nord- hausen. LE COHU, R., 1991: Morphologie des valves et du cingulum chez Aulacoseira ambigua (Grun.) Simonsen (Bacillariophycées). Quelques observations sur les phases pré- et postauxospores. Nova Hedwigia 53, 409–421. LIKHOSHWAY, Y. V., CRAWFORD, R. M., 2001: The rimoportula – a neglected feature in the systematics of Aulacoseira. Proceedings 16 International Diatom Symposium, Athens, 33–47. MESSERLI, B., GROSJEAN, M., HOFER, T., NÚÑEZ, L., PFISTER, C., 2000: From nature-domi- nated to human-dominated environmental changes. Quaternary Science Reviews 19, 459–479. PATRICK, R., REIMER, C., 1966: The diatoms of the United States, exclusive of Alaska and Hawaii. Monogr. 13. Vol. 1. The Academy of Natural Sciences of Philadelphia, Phila- delphia. PATRICK, R., REIMER, C., 1975: The diatoms of the United States, Exclusive of Alaska and Hawaii. Monogr. 13. Vol. 2. The Academy of Natural Sciences of Philadelphia, Phila- delphia. PIELOU, E. C., 1969; An introduction to mathematical ecology. John Wiley and Sons, New York. PRITCHARD, A., 1861: A history of Infusoria, including the Desmidiaceae and Diato- maceae, British and foreign. Whittaker Imprint, London. SHANNON, C. E., WEAVER, W., 1949: The mathematical theory of communication. Univer- sity of Illinois Press, Urbana Il. SIMONSEN, R., 1979: The diatom system: ideas on phylogeny. Bacillaria 2, 9–71. SIMPSON, E. H., 1949: Measurement of diversity. Nature 163, 688. SIVER, P. A., KLING, H., 1997: Morphological observations of Aulacoseira using scanning electron microscopy. Canadian Journal of Botany 75, 1807–1835. SIVER, P., HAMILTON, P., 2005: Aulacoseira nygardii. Nova Hedwigia 81, 257–265. SIVER, P. A., HAMILTON, P. B., STACHURA-SUKHOPLES, K., KOCIOLEK, J. P., 2005: Diatoms of North America. The freshwater flora of Cape Cod. Iconographia Diatomologica, 1–463. STEVENSON, R. J., WILEY, M. J., GAGE, S. H., LOUGHEED, V. L., RISENG, C. M., BONNELL, P., BURTON, T. M., HOUGH, R. A., HYNDMAN, D. W., KOCHES, J. K., LONG, D. T., PIJANOW- SKI, B. C., QI, J., STEINMAN, A. D., UZARSKI, D. G., 2007: Watershed science: essential, complex, multidisciplinary and collaboratory. In: JI, W. (ed.), Wetland and water re- source modelling and assessment, 231–246. CRC Press, Taylor and Francis Group, Boca Raton, Florida. STOERMER, E. F., KREIS, R. G., SICKO-GOAD, L., 1981: A systematic, quantitative and eco- logical comparison of Melosira islandica O. Müll. with A. granulata (Ehr.) Ralfs from the Laurentian Great Lakes. Journal of Great Lakes Research 7, 345–356. 418 ACTA BOT. CROAT. 68 (2), 2009 MANOYLOV K. M., OGNJANOVA-RUMENOVA N., STEVENSON R. J. U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:52 Color profile: Disabled Composite 150 lpi at 45 degrees STOERMER, E. F., WOLIN, J. A., SCHELSKE, C. L., CONLEY, D. J., 1985: An assessment of eco- logical changes during the recent history of Lake Ontario based of siliceous micro- fossils preserved in the sediment. Journal of Phycology 21, 414–418. STOERMER, E. F., SMOL, J. P., 1999: The Diatoms: Application for the Environmental and Earth Sciences. University Press, Cambridge. STONE, J. R., FRITZ, S. C., 2004: Three-dimensional modelling of lacustrine diatom habitat areas: Improving paleolimnological interpretation of planktic:benthic ratios. Limnol- ogy and Oceanography 49, 1540–1548. TRIFONOVA, I., GENKAL, S., 2001: Species of the genus Aulacoseira Twaites in lakes and rivers of north-western Russia-distribution and ecology. Proceedings 16 International Diatom Symposium, Athens, 315–323. TUJI, A., HOUKI, A., 2004: Taxonomy, ultrastructure, and biogeography of the Aulacoseira subarctica species complex. Bulletin of the National Science Museum Tokyo, Ser. B 30, 35–54. USOLTSEVA, M. V., LIKHOSHWAY, Y. V., 2007: The fine structure of loricae in the species of the genus Aulacoseira Thwaites (Bacillariophyta) from Ob’ River (Russia). Algologia 17, 139–152. VAN DAM, H., MERTENS, A., SINKELDAM, J., 1994: A coded checklist and ecological indica- tor values of freshwater diatoms from the Netherlands. Netherlands Journal of Aquatic Ecology 28, 117–133. VAN HEURCK, H., 1880–1885: Synopsis des diatomées de Belgique. Atlas, Anvers. WILKINSON, L., 1989: Systat, The system for statistics. Evanston, Illinois. WOLFE, A. P., EDLUND, M. B., 2005: Taxonomy, phylogeny, and paleoecology of Eoseira wilsonii gen. et sp. nov., (Bacillariophyceae: Aulacoseiraceae) from lake sediments at Horsefly, British Columbia, Canada. Canadian Journal of Earth Sciences 42, 243–257. WOLIN, J. A., 1996: Late Holocene lake-level and lake-development signals in Lower Her- ring Lake, Michigan. Journal of Paleolimnology 15, 19–45. WOLIN, J. A., DUTHIE, H. C., 1999: Diatoms as indicators of water level changes in freshwater lakes. In: STOERMER, E. F., SMOL, J. P. (eds.), The diatoms: application for the environ- mental and Earth sciences, 183–202. University Press, Cambridge. WOLIN, J.A., STOERMER, E.F., 2005: Response of a Lake Michigan coastal lake to anthro- pogenic catchment disturbance. Journal of Paleolimnology 33, 73–94. YANG, X., WANG, S., SHEN, J., ZHU Y., ZHANG, Z., WU, Y., 2002: Lacustrine environement responses to human activities in the past 300 years in Longgan Lake catchment, south- east China. Science in China 45, 709–718. YANG, X., ANDERSON, N. J., DONG, X., SHEN, J. I., 2008: Surface sediment diatom assem- blages and epilimnetic total phosphorus in large, shallow lakes of the Yangtze flood- plain: their relationships and implications for assessing long-term eutrophication. Freshwater Biology 53, 1273–1290. ZOHARY, T., 2004: Changes to the phytoplankton assemblage of Lake Kinneret after de- cades of predictable, repetitive pattern. Freshwater Biology 49, 1355–1371. ACTA BOT. CROAT. 68 (2), 2009 419 AULACOSEIRA SPECIES IN SEDIMENTS U:\ACTA BOTANICA\Acta-Botan 2-09\Manoylov.vp 6. listopad 2009 12:38:52 Color profile: Disabled Composite 150 lpi at 45 degrees