Wisconsin desmids. II. Aufwuchs and plankton communities of selected soft water lakes,hard water lakes and calcareous spring ponds

This report summarizes the results of summer studies of five soft water lakes, five hard water lakes and six calcareous spring ponds in Wisconsin with respect to the composition of the plankton and aufwuchs communities and the relative role of desmids in those communities. The results are compared with similar data obtained from selected acid bog lakes, alkaline bog lakes and closed bogs. Soft water lakes harbored a greater aufwuchs and plankton desmid diversity than hard water lakes or spring ponds; however, diversity in acid bog lakes was substantially greater than in any other lake type. Utricularia contained the greatest desmid diversity and population density in every lake where it occurred. Staurastrum was the most prevalent genus in the plankton and it was the only one recorded from hard water lakes and calcareous spring ponds. Desmid aufwuchs population densities were roughly comparable in hard water lakes, soft water lakes and acid bogs and the contribution of desmids to the total aufwuchs population was similar for the latter two lake types. However, the plankton of acid bog lakes generally harbored substantially greater desmid populations and these populations contributed much more to the total population than in any other lake type. Aufwuchs data are presented for several hosts and comparisons of population densities are given among hosts within a given lake and between the same host in different lakes of a given type. Data for other algal groups are also included.     

Rare and new desmids (Desmidiaceae, Chlorophyta) from Japan

A number of rare or unknown desmid species were revealed in samples collected from a range of aquatic habitats in Japan. In the present paper we describe one new species of the family Desmidiaceae, Staurastrum tsukubicum sp. nov. and report the presence in Japan of two species, Staurastrum levanderi Grönbl. and Cos-marium dilatatum Lütkem. in Järnefelt et Grönblad, previously found only in Europe. One taxon, Euastrum englerii Schmidle var. madagascariense Bourr. et Manguin, is renamed as Euastrum biverrucosum nom. nov. et stat. nov. The morphology of these taxa was studied using light and scanning electron microscopy and their taxonomic affinities are discussed.     

Spatial heterogeneity of periphytic microbial communities in a small pesticide-polluted river

Spatial variability in the microbial community composition of river biofilms was investigated in a small river using two spatial scales: one monitored the upstream–downstream pesticide contamination gradient, referred to as the 'between-section variability', and the other monitored a 100-m longitudinal transect (eight sampling sites per section) within each sampling section, referred to as the 'within-section variability'. Periphyton samples were collected in spring and winter on artificial substrates placed in the main channel of the river. Denaturing gradient gel electrophoresis (DGGE) was used to assess the prokaryotic and eukaryotic community richness and diversity, and HPLC pigment analysis to assess the global taxonomic composition of the photoautotrophic community. In order to try to reduce the biological variability due to differences in flow velocity and in light conditions within each sampling section, and consequently to take into account only the changes due to water chemistry, nine plates (three per sampling section) subjected to similar physical conditions were chosen, and the results for these plates were compared with those obtained for all 24 plates. As shown by DGGE and by HPLC analyses, using these three substrate plates exposed to similar environmental conditions did indeed reduce the within-section variability and maximize the between-section variability. This sampling strategy also improved the evaluation of the impact of pollutants on the periphytic communities, measured using short-term sensitivity testing.     

Diversity of desmids in three Thai peat swamps

Three peat swamps situated in the southern part of Thailand were investigated for their desmid flora in relation to a number of physical and chemical habitat parameters. Altogether, 99 species were encountered belonging to 22 genera. 30 species are new records for the Thai desmid flora. Laempagarung peat swamp showed the highest diversity (45 species), followed by Maikhao peat swamp (32 species) and Jud peat swamp (25 species). Despite its relatively low species richness, Jud swamp appeared to house a number of rare taxa, e.g., Micrasterias subdenticulata var. ornata, M. suboblonga var. tecta and M. tetraptera var. siamensis which can be considered Indo-Malaysian endemics. Differences in composition of the desmid flora between the three peat swamps are discussed in relation to environmental conditions. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Distribution and seasonality of desmids in the Maarsseveen Lakes area

The desmid flora of mesotrophic Lake Maarsseveen I, eutrophic Lake Maarsseveen II, as well as the interconnecting broads was studied during the period 1987–1991. Seasonal perodicity of euplanktonicStaurastrum andCosmarium species in the two Maarsseveen lakes fitted the well-known general pattern of desmid abundance peaks in (late) summer time. The deviating seasonality of two euplanktonicClosterium species (C. aciculare andC. acutum var.variabile) could be related to special nutritional demands. The tychoplanktonic desmid flora encountered in the interconnecting system of peat pits and canals proved to be more diversified as the influence of nutrient-poor seepage on the habitat (appearing from conductivity, transparency and the occurrence of particular macrophyte species) was greater. The rare speciesEuastrum germanicum andHeimansia pusilla had been only incidentally recorded in The Netherlands. Hanny Kooyman-van Blokland untimely died at the age of forty, in March 1994.     

Restoration of eutrophied shallow softwater lakes based upon carbon and phosphorus limitation

Plant communities from oligotrophic, poorly buffered waters are seriously threatened by both, acidification and eutrophication/alkalinization. Acidification is mainly caused by atmospheric deposition of acidifying substances while eutrophication is often the result of inlet of nutrient enriched, calcareous brook- or groundwater. The plant production in very soft waters is often limited by low levels of inorganic carbon, nitrogen and/or phosphorus. This paper deals with the possibilities for restoration of formerly oligotrophic but now eutrophied and alkalinized softwater systems. Restoration based upon nitrogen limitation is not likely to be successful as the atmospheric deposition of nitrogen in The Netherlands is very high. Phosphorus limitation can also be a problem. One can stop the input of phosphorus and remove the mud layer, but the problem remains that also the deeper mineral sandy sediments are saturated with phosphate. A possible remedy, however, is a combination of carbon- and phosphorus limitation. Many plants from eutrophic environments never occur in very soft waters, probably as a result of carbon limitation. In addition, mobilisation of phosphate is much lower in waters with very low bicarbonate levels. Restoration of a former oligotrophic softwater lake by reducing the inlet of calcareous surface water, in combination with removal of the organic sediment layer, appeared to be very successful. Many endangered plant species such asIsoetes echinospora, Luronium natans, Deschampsia setacea andEchinodorus repens developed spontaneously from the still viable seedbank.     

Plant community structure determines primary productivity in shallow,eutrophic lakes

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The ecology of periphytic rotifers

The ecology of rotifer assemblages in the periphyton has received little attention relative to that of pelagic rotifers. This paper reviews the ecology of periphytic rotifers, with particular emphasis on the role of macrophytes in the structuring of rotifer assemblages spatially and temporally, and compares these aspects with the dynamics of better known pelagic rotifer communities. Littoral rotifer periphyton communities are typically diverse in lakes, and have composition dissimilar to that of the open water. In rivers, diversity and composition in the pelagic and littoral appear to be similar. Rotifers show preference for macrophyte species they associate with, probably through differences in physical structure or complexity, food concentration or composition, chemical factors, macrophyte age, and differences in the degree of protection from predation provided by macrophytes. These mechanisms are in general not well investigated in rotifers. Factors affecting the seasonal dynamics of periphytic communities appear to be similar to pelagic communities, with seasonal dynamics of substrates and disturbance by flooding or drying also being important.     

Phytoplankton in 63 limed lakes in comparison with the distribution in 500 untreated lakes with varying pH

As a result of the different weathering of lime in soils and varying acid deposition, the pH of Swedish oligotrophic lake waters has a broad range from ca. 4 to 8.5. Phytoplankton species occur in all lakes, but the composition and species richness varies in relation to pH. The maximum number of taxa was recorded within the pH-range 7.0–7.6, while the number decreased at higher pH and especially at pH below 5.6. During 1975–1985, thousands of lakes in Sweden were limed with the intention to restore biotic diversity and production. In order to find out whether there are differences in quality between limed and unacidified waters, the distribution of 57 selected phytoplankton taxa in 63 limed lakes was compared with that in 500 unlimed lakes with varying pH. The study shows that most common species in unacidified lakes also occur in the limed ones. However, several species of Cyanophyceae and Conjugatophyceae were missing especially in lakes that were strongly acidified before liming. On the other hand, some taxa were more frequent in the limed lakes.     

Some new taxa of desmids from the Andaman Islands,India

Two new species, five new varieties and five new forms belonging to the desmid genera Closterium Nitzsch, Pleurotaenium Naeg., Euastridium W. & W., Micrasterias Agardh, Cosmarium Corda and Staurastrum Meyen from the Andaman Islands are described.     

Combined stable isotope and gut contents analysis of food webs in plant-dominated, shallow lakes

Summary 1. To determine feeding links between primary producers, invertebrates and fish, stable isotope analyses and gut content analyses of fish were conducted on the components of four shallow, eutrophic to hypertrophic, plant-dominated lakes.
2. Although separation of basal resources was possible, the diets of both fish and invertebrates were broad, comprising food from different compartments (planktonic, epiphytic/benthic), as well as from different trophic levels.
3. Mixing models were used to determine the extent to which periphyton production supported higher trophic levels. Only one species of invertebrate relied upon periphyton production exclusively.
4. Fish density affected the diets of invertebrates. The response was different for planktonic and epiphytic/benthic invertebrates. The proportion of periphyton production in the diets of zooplankton appeared to increase with fish density, whilst it decreased for other invertebrates.
5. As all zooplankton samples were collected in the open water at dusk, these results are further evidence for the diurnal horizontal migration of zooplankton. Although not conclusive, they are consistent with a behavioural response by invertebrates and zooplankton in the presence of fish.     

A method for quantifying conservation value in lentic freshwater habitats using desmids as indicator organisms

A method is presented for quantification of aquatic nature conservation value based on desmid assemblages present. Species richness (indicative of internal structural and functional differentiation of the ecosystem), the occurrence of rare taxa (often indicative of particular environmental conditions) and the presence of species indicative of ecosystem maturity are the parameters chosen to determine conservation value. For the sake of utility, schemes have been developed to transform the values scored for the various parameters to a simple scale ranging from 0 to 10, relative to regional and historical standards. By way of illustration, two examples are presented. The first shows the decline of desmid-related conservation value along a gradient of increasing eutrophication in a series of interconnected shallow lakes, the other illustrates the course of this value through time in a polluted and subsequently restored moorland pool.     

Phosphate limitation influences the sensitivity to copper in periphytic algae

1. To assess the influence of nutrient limitation on copper toxicity, periphitic communities from an oligotrophic stream were exposed to copper for six to 12 days with and without the supply of nutrients (mainly P). 2. In contrast to the hypothesis that nutrient cycling in mature biofilms would protect them from Cu toxicity, low and high biomass biofilms did not differ in their physiological response to copper after 6 days of exposure. 3. A clear influence of P‐limitation on copper toxicity was observed. Periphytic communities that were previously fertilised for 18 days were three times more tolerant than control communities indicating that P‐limitation enhanced Cu toxicity and tolerance induction were probably related to the higher P‐availability. In addition, a compensation of Cu toxicity after P‐addition was observed in the long‐term (after 12 days). 4. We conclude that periphyton from oligotrophic streams is more sensitive to copper than periphyton from fertilised streams, and that therefore a higher effect of chronic copper exposure is expected to occur in oligotrophic P‐limited fluvial systems. 5. Extrapolation of our results to the area of study (Catalonia, north‐east of Spain) indicates that while the levels of Cu commonly found in the zone may negatively affect the periphyton from oligotrophic streams, because of the interaction between Cu and P, they are not able to control the growth of nuisance algae which is common under high nutrient conditions.     

Biological and ecological features of saline lakes in northern Tibet,China

In May and July 2001, the biological and ecological features of 22 salt lakes in northern Tibet , China, were investigated.Their salinity ranged from 1 to 390 g l^–1. One hundred and thirty two samples were collected. Ninty five taxa of phytoplankton and 42 taxa of zooplankton were recorded. The dominant cation was sodium, with magnesium generally sub-dominant; CO₃^2– was the dominant anion in low salinity, chloride was the dominant anion with increasing salinity. Major species were Gloeothece linearis, Oscillatoria tenuis, Chroococcus minutus (blue-green algae); Navicula spp, Cymbella pusilla, Diatoma elongatum(diatoms); Dunaliella salina, Chlorella vulgarisand Ulothrix tenerrima (green algae). Major zooplankton included: Vorticella campanula, Epistylis daphniae (Protista); Keratella quadrata, Brachionus plicatilis (Rotifera); Artemiaspp. (Anostraca); Daphniopsis tibetana (Cladocera); Cletocamptus dertersiand Cyclops vicinus (Copepoda). Ten species were recorded in hypersaline waters; apart from those metioned above, they included CyclidiumsppLitonotus fasciola, Euplotes terricola, Strombilidium viride, Brachionus variabilis, Colurella adriatica, Keratella cochlearis, Colurella adriatica, and Cyclops sp. Seven taxa of benthic macroinvertebrates are recorded, represented by Cyprissp. (Ostracoda), Gammarus sp. (Amphipoda), Radixsp. and Hippeutis sp. (Mollusca); chiroonomids Tendipus group salinarius (Diptera), Nematoda, Trochophora and Ephrdra sp. At present, there are fishes only in Bangong Co., and no fishes recorded in other salt lakes. The total number of plankton species has a significantly negative correlation with the salinity, and decreased with increasing altitude, but not significant.     

Some new and interesting ecological observations on desmids from the Province of Vojvodina (Northern Serbia)

A detailed qualitative investigation of the desmid community in the territory of the Province of Vojvodina (Northern Serbia, part of the Pannonian Plain) revealed a surprisingly high number of desmid taxa. Although most of the desmids were marked as rare, according to the results of physico-chemical analyses of water samples, several taxa were frequently recorded in habitats that are generally deemed unsuitable for desmids. The ecological characteristics of 18 desmid taxa, some of which known as acidophilic and/or oligotrophic, are briefly discussed. The unexpected presence of many desmid taxa is explained by assuming that their tolerance threshold to various physico-chemical parameters has changed considerably. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Effects of cadmium stress on periphytic diatom communities in indoor artificial streams

SUMMARY 1. Two experiments were performed with periphytic diatoms originating from the River Lot (France) and allowed to grow on clean substrata within indoor artificial streams. Three cadmium (Cd) levels (control, low Cd=10 μg L⁻¹ and high Cd=100 μg L⁻¹) were used to test the effects of Cd on (i) the settlement and development of diatom communities (Experiment 1, 4 weeks Cd exposure) and (ii) predeveloped communities grown over a 2-week period without contamination (Experiment 2, 2 weeks Cd exposure).
2. Experiment 1 revealed that growth and taxonomic composition of diatom communities clearly differed with Cd exposure. Biofilms were more adpressed to substrata under low Cd concentration, and were thinner and patchy under high Cd concentration.
3. Exposure of developed diatom communities (Experiment 2) to Cd revealed only minor variations in taxonomic composition, possibly linked to the protective role of the developed organic matrix against metal stress.
4. These results support the validity of periphytic diatom communities as indicators of metal pollution, although significant structural changes would take longer within developed communities.     

Spring phytoplankton of 54 small lakes in southern Finland

The abundance and species composition of phytoplankton communities were studied rapidly following the spring ice-melt in 54 small Finnish lakes that form a unique mosaic of water bodies. Phytoplankton biomass and cell density varied among the study lakes with a factor 100 between the lowest and highest values. Highest biomass and densities of phytoplankton characterized small ( < 0.05 km²) lakes with moderate or high water colour (> 80 mg Pt l^–1). In contrast, biomass was low in clear-water lakes and lakes where water throughflow was strong. Typically one species dominated most phytoplankton communities, and usually comprised up to about 45% of the total phytoplankton biomass. Two-thirds of the 103 taxa observed were Chrysophyceans and Chlorophyceans. The most common taxa wereChlamydomonas spp. (Chlorophyceae) andCryptomonas ovata (Cryptophyceae).