Toxic Microcystis is Widespread in Lake Erie: PCR Detection of Toxin Genes and Molecular Characterization of Associated Cyanobacterial Communities

During the past decade, algae blooms, which include the toxic cyanobacterium Microcystis, have reoccurred in the Laurentian Great Lakes, most commonly in the western basin of Lake Erie. Whereas the western basin is the most impacted by toxic Microcystis in Lake Erie, there has historically been little effort focused on identifying the spatial distribution of Microcystis throughout this lake. To address this lack of knowledge, we have employed a polymerase-chain-reaction-based detection of genes required for synthesis of the toxin microcystin (mcyD and mcyB), as well as 16S rDNA fragments specific to either all Microcystis or all cyanobacteria. Using a multiplex approach, we tested 21 samples from 13 field stations and found that toxigenic Microcystis were present in the western and eastern basins in the summers of 1999, 2000, and 2002 and the central basin in 1999 and 2002. This is the most extensive distribution of Microcystis reported in Lake Erie. Clone libraries (16S rDNA) of these cyanobacterial communities were generated from 7 of the 13 field stations (representing all three basins) to partially characterize this microbial community. These libraries were shown to be dominated by sequences assigned to the Synechococcus and Cyanobium phylogenetic cluster, indicating the importance of picoplankton in this large lake system.     

Marine and freshwater cyanophages in a Laurentian Great Lake: evidence from infectivity assays and molecular analyses of g20 genes

While it is well established that viruses play an important role in the structure of marine microbial food webs, few studies have directly addressed their role in large lake systems. As part of an ongoing study of the microbial ecology of Lake Erie, we have examined the distribution and diversity of viruses in this system. One surprising result has been the pervasive distribution of cyanophages that infect the marine cyanobacterial isolate Synechococcus sp. strain WH7803. Viruses that lytically infect this cyanobacterium were identified throughout the western basin of Lake Erie, as well as in locations within the central and eastern basins. Analyses of the gene encoding the g20 viral capsid assembly protein (a conservative phylogenetic marker for the cyanophage) indicate that these viruses, as well as amplicons from natural populations and the ballast of commercial ships, are related to marine cyanophages but in some cases form a unique clade, leaving questions concerning the native hosts of these viruses. The results suggest that cyanophages may be as important in freshwater systems as they are known to be in marine systems.     

Marine and Freshwater Cyanophages in a Laurentian Great Lake: Evidence from Infectivity Assays and Molecular Analyses of g20 Genes

While it is well established that viruses play an important role in the structure of marine microbial food webs, few studies have directly addressed their role in large lake systems. As part of an ongoing study of the microbial ecology of Lake Erie, we have examined the distribution and diversity of viruses in this system. One surprising result has been the pervasive distribution of cyanophages that infect the marine cyanobacterial isolate Synechococcus sp. strain WH7803. Viruses that lytically infect this cyanobacterium were identified throughout the western basin of Lake Erie, as well as in locations within the central and eastern basins. Analyses of the gene encoding the g20 viral capsid assembly protein (a conservative phylogenetic marker for the cyanophage) indicate that these viruses, as well as amplicons from natural populations and the ballast of commercial ships, are related to marine cyanophages but in some cases form a unique clade, leaving questions concerning the native hosts of these viruses. The results suggest that cyanophages may be as important in freshwater systems as they are known to be in marine systems.     

Activity profiles of bacterioplankton in a eutrophic river

1. The significance of microbial diversity in processing dissolved organic matter (DOM) is largely unknown. We investigated the range of functional diversity in the bacterioplankton from a eutrophic river by profiling extracellular enzyme activities (EEA) and substrate-induced respiration (SIR) patterns.
2. The EEA profiles consisted of assays for 21 hydrolases, measured using fluorogenic substrates arrayed on 96-well microplates. Commercially available BiOLOG^® GN and ECO plates, which contained 120 different substrates, were used for the SIR profiles.
3. The EEA data were more dynamic than the SIR. Five enzymes, leucine aminopeptidase, alkaline phosphatase, alanine aminopeptidase, arginine aminopeptidase and β-glucosidase, showed consistently high activity; ten others were ubiquitous at lower activity levels; the remainder were detected intermittently. The SIR data showed less temporal variability. With one exception (citrate), the 20 substrates that generated the largest responses were all saccharides or their derivatives.
4. The EEA and SIR data did not generally correlate. Both methods were effective for ordinating bacterioplankton although, unlike the SIR, the EEA ordination followed a clear temporal trajectory.
5. Because the SIR profiles are based on a culture response, whilst the EEA profiles measure activity of the extant community, the latter appear to be more directly linked to the mechanics of DOM processing.     

Preliminary analysis to estimate the spatial distribution of benefits of P load reduction: Identifying the spatial influence of phosphorus loading from the Maumee River (USA) in western Lake Erie

Since the early 2000s, Lake Erie has been experiencing annual cyanobacterial blooms that often cover large portions of the western basin and even reach into the central basin. These blooms have affected several ecosystem services provided by Lake Erie to surrounding communities (notably drinking water quality). Several modeling efforts have identified the springtime total bioavailable phosphorus (TBP) load as a major driver of maximum cyanobacterial biomass in western Lake Erie, and on this basis, international water management bodies have set a phosphorus (P) reduction goal. This P reduction goal is intended to reduce maximum cyanobacterial biomass, but there has been very limited effort to identify the specific locations within the western basin of Lake Erie that will likely experience the most benefits. Here, we used pixel‐specific linear regression to identify where annual variation in spring TBP loads is most strongly associated with cyanobacterial abundance, as inferred from satellite imagery. Using this approach, we find that annual TBP loads are most strongly associated with cyanobacterial abundance in the central and southern areas of the western basin. At the location of the Toledo water intake, the association between TBP load and cyanobacterial abundance is moderate, and in Maumee Bay (near Toledo, Ohio), the association between TBP and cyanobacterial abundance is no better than a null model. Both of these locations are important for the delivery of specific ecosystem services, but this analysis indicates that P load reductions would not be expected to substantially improve maximum annual cyanobacterial abundance in these locations. These results are preliminary in the sense that only a limited set of models were tested in this analysis, but these results illustrate the importance of identifying whether the spatial distribution of management benefits (in this case P load reduction) matches the spatial distribution of management goals (reducing the effects of cyanobacteria on important ecosystem services).     

Spatial and temporal patterns in maternal energetic traits of yellow perch (Perca flavescens) in Lake Erie

1. For many fish species, survival during early life stages is linked to the size and energetic condition of females prior to reproduction. For example, females in good energetic condition are often more fecund and produce larger eggs and offspring than those in poor condition. 2. We measured the characteristics of female yellow perch (Perca flavescens) that may influence annual population fluctuations. From 2005 to 2007, we measured spatial variation in female reproductive traits, such as age, length, mass and energy density (J g^?1) of somatic tissues and ovaries among four spawning aggregations of yellow perch in western and central Lake Erie. 3. Maternal traits, such as somatic energy density and spawner age distribution, differed between the western and central basin, whereas reproductive traits, such as fecundity and ovarian energy density, differed across years. 4. To understand the implications of observed differences in demographic rates (growth and mortality rates) between basins, we developed a deterministic model to simulate the total egg production in the western and central basins under different scenarios of fishing mortality. 5. High growth rates and low mortality rates combined to produce higher modelled estimates of total egg production in the central than in the western basin, and a larger proportion of eggs were produced by old age classes in the central basin than in the western basin. 6. Our results demonstrate that changing harvest levels for populations with different demographic rates can influence total reproductive output through complex interactions between age‐specific mortality, growth and size‐specific fecundity, which has implications for the population dynamics of yellow perch and related species across a broad geographic range.     

Enzymatic Activities and Prokaryotic Abundance in Relation to Organic Matter along a West–East Mediterranean Transect (TRANSMED Cruise)

The distribution of extracellular enzymatic activities (EEA) [leucine aminopeptidase (LAP), ?-glucosidase (GLU), alkaline phosphatase (AP)], as well as that of prokaryotic abundance (PA) and biomass (PB), dissolved organic carbon (DOC), particulate organic carbon and particulate total nitrogen (POC, PTN), was determined in the epi-, meso-, and bathypelagic waters of the Mediterranean Sea along a West-East transect and at one Atlantic station located outside the Strait of Gibraltar. This study represents a synoptical evaluation of the microbial metabolism during early summer. Decreasing trends with depth were observed for most of the parameters (PA, PB, AP, DOC, POC, PTN). Significant differences between the western and eastern basins of the Mediterranean Sea were found, displaying higher rates of LAP and GLU and lower C/N ratios more in the eastern than in the western areas. Conversely, in the epipelagic layer, PA and PB were found to be higher in the western than in the eastern basins. PB was significantly related to DOC concentration (all data, n = 145, r = 0.53, P < 0.01), while significant correlations of EEA with POC and PTN were found in the epipelagic layer, indicating an active response of microbial metabolism to organic substrates. Specific enzyme activities normalized to cell abundance pointed out high values of LAP and GLU in the bathypelagic layer, especially in the eastern basin, while cell-specific AP was high in the epi- and bathypelagic zone of the eastern basin indicating a rapid regeneration of inorganic P for both prokaryotes and phytoplankton needs. Low activity and abundance characterized the Atlantic station, while opposite trends of these parameters were observed along the Mediterranean transect, showing the uncoupling between abundance and activity data. In the east Mediterranean Sea, decomposition processes increased probably in response to mesoscale structures which lead to organic matter downwelling.     

Landscape genetic patterns of the rainbow darter Etheostoma caeruleum: a catchment analysis of mitochondrial DNA sequences and nuclear microsatellites

Catchment population structure and divergence patterns of the rainbow darter Etheostoma caeruleum (Percidae: Teleostei), an eastern North American benthic fish, are tested using a landscape genetics approach. Allelic variation at eight nuclear DNA microsatellite loci and two mitochondrial DNA regions [cytochrome (cyt) b gene and control region; 2056 aligned base pairs (bp)] is analysed from 89 individuals and six sites in the Lake Erie catchment (Blanchard, Chagrin, Cuyahoga and Grand Rivers) v. the Ohio River catchment (Big Darby Creek and Little Miami River). Genetic and geographic patterning is assessed using phylogenetic trees, pair‐wise F_ST analogues, AMOVA partitioning, Mantel regression, Bayesian assignment, 3D factorial correspondence and barrier analyses. Results identify 34 cyt b haplotypes, 22 control region haplotypes and 137 microsatellite alleles whose distributions demonstrate marked genetic divergence between populations from the Lake Erie and Ohio River catchments. Etheostoma caeruleum populations in the Lake Erie and Ohio River catchments diverged c. 1·6 mya during the Pleistocene glaciations. Greater genetic separations characterize the Ohio River populations, reflecting their older habitat age and less recent connectivity. Divergence levels within the Lake Erie catchment denote more recent post‐glacial origins. Notably, the western Lake Erie Blanchard River population markedly differs from the three central basin tributary samples, which are each genetically distinguishable using microsatellites. Overall relationships among the Lake Erie sites refute a genetic isolation by geographic distance hypothesis. Etheostoma caeruleum populations thus exchange few genes and have low migration among tributaries and catchments.     

Testing a typology system of running waters for conservation planning in Hungary

The zebra mussel (Dreissena polymorpha) and its congener the quagga mussel (Dreissena rostriformis bugensis) are both invaders in freshwater, but have very different invasion histories, with zebra mussels attaining substantially faster rates of spread at virtually all spatial scales. However, in waterbodies where they co-occur, D. r. bugensis can displace D. polymorpha. To determine if the mechanisms for this displacement are associated with different survival and growth, we kept mussels in flow-through tanks for 289 days with two temperature regimes that mimicked the natural surface water (littoral zone) and hypolimnion conditions of Lake Erie. For the littoral zone regime, we used water directly from the surface of Lake Erie (range 4–25°C, average 11.9 ± 0.6°C). For the profundal zone treatment, Lake Erie surface water was chilled to about 6°C (range 5–8°C, average 6.2 ± 0.6°C) for the full duration of the experiment. For each of these temperature regimes, we used three replicate tanks with only zebra mussels present and three replicate tanks with only quagga mussels (150 ind./tank each), and three replicate tanks with both species (75 ind./tank of each species). Quagga mussels had higher survivorship and grew more than zebra mussels in all treatments. For both species, the size of the mussel entering the winter was critical for survivorship. Larger mussels had a higher survival over the winter in all treatments. For both species, there was a survivorship and growth tradeoff. In the warmer littoral zone treatment both species had higher growth, but lower survival than in the colder profundal zone treatment. Surprisingly, although quagga mussels outperformed zebra mussels, zebra mussel survivorship was better when they were faced with competition by quagga mussels than with just intraspecific competition. In addition, quagga mussels suffered size-specific mortality during the growing season only when facing interspecific competition with zebra mussels. Further experiments are needed to determine the possible mechanisms for these interspecific effects.     

Mortality of young-of-the-year rainbow smelt (Osmerus mordax) in Lake Erie associated with the occurrence of Glugea hertwigi

An extensive mortality of young-of-the-year rainbow smelt (Osmerus mordax) occurred in Lake Erie during the fall of 1969. Dead and dying smelt were observed along the north shore from west of Long Point in the central basin to Port Maitland in the eastern basin. No other fish species was involved. Glugea hertwigi, a microsporidan parasite, was observed in 90% of the distressed smelt examined, and is believed to have been a major contributing factor to the mortality.     

Mineralization of glucose and lignocellulose by four arctic freshwater sediments in response to nutrient enrichment.

Microbial biomass and activity were examined in four different arctic sediments: littoral lake sediment and profundal lake sediment from Toolik Lake, Alaska, thaw pond sediment, and eroding river bank peat. The thaw pond sediment had the largest viable microbial biomass, while the profundal sediment had the smallest. Rates of glucose or acetate incorporation into lipids, glucose mineralization, and lignocellulose mineralization (all normalized per unit of biomass) were highest in the river peat sample, however. The kinetics of glucose mineralization in the profundal sediment were very different from those in the other three samples: although the initial rate of mineralization was five times lower than that in the peat and two times lower than that in the littoral and thaw pond sediments, the maximum amount of 14CO2 evolved from [14C]glucose eventually equaled that in the peat and exceeded that in the littoral and thaw pond sediments by 2.0 and 3.5 times, respectively. Carex aquatilis [14C-cellulose]- and [14C-lignin]lignocellulose mineralization rates in the profundal sediment equaled or exceeded those in the littoral sediment after 16 and 46 days, but the pattern of nutrient limitation differed: the profundal sediment was the only one sampled that exhibited nitrogen limitation, while the other three sediments appeared to be limited primarily by phosphorus. The addition of nitrogen and phosphorus together had no cumulative effects on lignocellulose mineralization. When the rates of mineralization or incorporation of glucose are compared with those of lignocellulose, the results of this study indicate that profundal sediment communities may be better able to utilize the more recalcitrant substrates relative to the labile substrates than microbial communities from sediments rich in detritus and standing macrophytes.     

Mineralization of glucose and lignocellulose by four arctic freshwater sediments in response to nutrient enrichment.

Microbial biomass and activity were examined in four different arctic sediments: littoral lake sediment and profundal lake sediment from Toolik Lake, Alaska, thaw pond sediment, and eroding river bank peat. The thaw pond sediment had the largest viable microbial biomass, while the profundal sediment had the smallest. Rates of glucose or acetate incorporation into lipids, glucose mineralization, and lignocellulose mineralization (all normalized per unit of biomass) were highest in the river peat sample, however. The kinetics of glucose mineralization in the profundal sediment were very different from those in the other three samples: although the initial rate of mineralization was five times lower than that in the peat and two times lower than that in the littoral and thaw pond sediments, the maximum amount of 14CO2 evolved from [14C]glucose eventually equaled that in the peat and exceeded that in the littoral and thaw pond sediments by 2.0 and 3.5 times, respectively. Carex aquatilis [14C-cellulose]- and [14C-lignin]lignocellulose mineralization rates in the profundal sediment equaled or exceeded those in the littoral sediment after 16 and 46 days, but the pattern of nutrient limitation differed: the profundal sediment was the only one sampled that exhibited nitrogen limitation, while the other three sediments appeared to be limited primarily by phosphorus. The addition of nitrogen and phosphorus together had no cumulative effects on lignocellulose mineralization. When the rates of mineralization or incorporation of glucose are compared with those of lignocellulose, the results of this study indicate that profundal sediment communities may be better able to utilize the more recalcitrant substrates relative to the labile substrates than microbial communities from sediments rich in detritus and standing macrophytes.     

Complex postglacial recolonization inferred from population genetic structure of mottled sculpin Cottus bairdii in tributaries of eastern Lake Michigan,U.S.A.

This study used analyses of the genetic structure of a non‐game fish species, the mottled sculpin Cottus bairdii to hypothesize probable recolonization routes used by cottids and possibly other Laurentian Great Lakes fishes following glacial recession. Based on samples from 16 small streams in five major Lake Michigan, U.S.A., tributary basins, significant interpopulation differentiation was documented (overall F_ST = 0·235). Differentiation was complex, however, with unexpectedly high genetic similarity among basins as well as occasionally strong differentiation within basins, despite relatively close geographic proximity of populations. Genetic dissimilarities were identified between eastern and western populations within river basins, with similarities existing between eastern and western populations across basins. Given such patterns, recolonization is hypothesized to have occurred on three occasions from more than one glacial refugium, with a secondary vicariant event resulting from reduction in the water level of ancestral Lake Michigan. By studying the phylogeography of a small, non‐game fish species, this study provides insight into recolonization dynamics of the region that could be difficult to infer from game species that are often broadly dispersed by humans.     

Littoral zone of Lake Ladoga: ecological state evaluation

The littoral zone of a lake is an important ecotone between terrestrial and aquatic systems. From the point of view of the lake ecosystem, much of the mineral, organic and toxic substances entering the lake from the drainage basin are transformed in the littoral zone by physical processes and biochemical pathways. The littoral zone of Lake Ladoga can be divided into three main regions: the shallow southern region, the fairly steep western and eastern shorelines, and the northern archipelago. In these regions, the communities of aquatic macrophytes, periphyton, phyto- and zooplankton and meio- and macrobenthos have been extensively studied. This paper presents numerical data on these communities, with special reference to comparisons between areas subjected to different degrees of anthropogenic loading. Most of the communities are characterized by high species diversity and spatial heterogeneity, especially among the macrophyte associations in which intensive production and decomposition takes place. Water dynamics and water exchange rate are the main abiotic factors in the formation of littoral communities. The characteristics of plant associations and bottom substrate, rather than pollution, appear as the most important factors structuring meio- and macrobenthic invertebrate communities in the littoral.     

Mesozooplankton and microzooplankton grazing during cyanobacterial blooms in the western basin of Lake Erie

Lake Erie is the most socioeconomically important and productive of the Laurentian (North American) Great Lakes. Since the mid-1990s cyanobacterial blooms dominated primarily by Microcystis have emerged to become annual, late summer events in the western basin of Lake Erie yet the effects of these blooms on food web dynamics and zooplankton grazing are unclear. From 2005 to 2007, grazing rates of cultured (Daphnia pulex) and natural assemblages of mesozooplankton and microzooplankton on five autotrophic populations were quantified during cyanobacterial blooms in western Lake Erie. While all groups of zooplankton grazed on all prey groups investigated, the grazing rates of natural and cultured mesozooplankton were inversely correlated with abundances of potentially toxic cyanobacteria (Microcystis, Anabaena, and Cylindrospermopsis; p < 0.05) while those of the in situ microzooplankton community were not. Microzooplankton grazed more rapidly and consistently on all groups of phytoplankton, including cyanobacteria, compared to both groups of mesozooplankton. Cyanobacteria displayed more rapid intrinsic cellular growth rates than other phytoplankton groups under enhanced nutrient concentrations suggesting that future nutrient loading to Lake Erie could exacerbate cyanobacterial blooms. In sum, while grazing rates of mesozooplankton are slowed by cyanobacterial blooms in the western basin of Lake Erie, microzooplankton are likely to play an important role in the top-down control of these blooms; this control could be weakened by any future increases in nutrient loads to Lake Erie.     

Local adaptation of microbial communities to heavy metal stress in polluted sediments of Lake Erie

Microbial communities must balance the assimilation of biologically necessary metals with resistance to toxic metal concentrations. To investigate the impact of heavy metal contaminants on microbial communities, we performed two experiments measuring extracellular enzyme activities (EEA) in polluted and unpolluted sediments of Lake Erie. In the first experiment, inoculations with moderate concentrations of copper and zinc appreciably diminished EEA from uncontaminated sites, whereas EEA from contaminated sediments increased or were only negligibly affected. In the second experiment, we compared the effects of three separate metals (i.e. copper, arsenic, and cadmium) on microbial community metabolism in polluted and unpolluted locations. Although copper and arsenic elicited differential effects by inhibiting EEA only in unpolluted sediments, cadmium inhibited EEA in both polluted and unpolluted sediments. Multivariate analyses of EEA from polluted sediments revealed direct associations among hydrolytic enzymes and inverse or absent associations between hydrolases and oxidases; these associations demonstrated resilience to heavy metal stress. In contrast, addition of heavy metals to unpolluted sediments appeared to have a higher impact on the multivariate pattern of EEA associations as revealed by an increase in the number of associations, more inverse relationships, and potential enzymatic trade-offs. The results of this study suggest community-level adaptations through the development of resistance mechanisms to the types and local levels of heavy metals in the environment.     

Seasonal distribution of thermotolerant free-living amoebae. II. Lake Issaqueena

A quantitative study of the seasonal distribution of thermotolerant (37 degrees C and 45 degrees C), small free-living amoebae (FLA) was conducted in Lake Issaqueena, a warm, monomictic lake with steep, sloping banks and a maximum basin depth of 10 m in the Piedmont region of South Carolina. Naegleria and Vahlkampfia were the most frequently encountered FLA in littoral sediment and surface water samples whereas Acanthamoeba was most commonly isolated from profundal sediment, especially during late summer. In the water column, FLA populations were highest in a persistent detrital layer; however, few amoebae were isolated from a massive (approximately 1.5 m thick) layer of Oscillatoria. The only N. fowleri isolated in this study was from the detrital layer. Discussion of the influence of differences in watershed and basin morphology on variations in the size and generic composition of FLA populations for the aquatic ecosystems of Lake Issaqueena and Willard's Pond is included.     

Expansion of tubenose gobies <Emphasis Type="Italic">Proterorhinus semilunaris</Emphasis> into western Lake Erie and potential effects on native species

The Eurasian freshwater tubenose goby Proterorhinus semilunaris (formerly Proterorhinus marmoratus) invaded the Laurentian Great Lakes in the 1990s, presumably via ballast water from transoceanic cargo ships. Tubenose gobies spread throughout Lake St. Clair, its tributaries, and the Detroit River system, and also are present in the Duluth-Superior harbor of Lake Superior. Using seines and bottom trawls, we collected 113 tubenose gobies between July 2007 and August 2009 at several locations in western Lake Erie. The number and range of sizes of specimens collected suggest that that tubenose gobies have become established and self-sustaining in the western basin of Lake Erie. Tubenose gobies reached maximum densities in sheltered areas with abundant macrophyte growth, which also is their common habitat in native northern Black Sea populations. The diet of tubenose gobies was almost exclusively invertebrates, suggesting dietary overlap with other benthic fishes, such as darters (Etheostoma spp. and Percina sp.), madtoms (Noturus spp.), and sculpins (Cottus spp.). A single mitochondrial DNA haplotype was identified, which is the most common haplotype found in the original colonization area in the Lake St. Clair region, suggesting a founder effect. Tubenose gobies, like round gobies Neogobius melanostomus, have early life stages that drift owing to vertical migration, which probably allowed them to spread from areas of colonization. The Lake St. Clair-Lake Erie corridor appears to have served as an avenue for them to spread to the western basin of Lake Erie, and abundance of shallow macrophyte-rich habitats may be a key factor facilitating their further expansion within Lake Erie and the remainder of the Laurentian Great Lakes.     

Distribution and summer diapause of Canthocamptus staphylinus (Jurine) (Copepoda: Harpacticoida) in Lake Ladoga

The spatial distribution of Canthocamptus staphylinus (Jurine) in Lake Ladoga was examined. C. staphylinus is one of the most numerous species of harpacticoids in the lake. It can dwell in almost all littoral biotopes. In profundal biotopes strongly exposed to anthropogenic influence (pollution and eutrophication) only this species of harpacticoid was found. A peculiarity of C. staphylinus biology is that in summer individuals are in the resting stage as cysts. In summer active individuals were found in littoral habitats at a water temperature of 20 °C, but their number was small in comparison with cold periods of the year. In the littoral zone the relative number of individuals in cysts was clearly related to water temperature. Twelve degrees temperature appears to be critical for development of littoral populations of C. staphylinus.     

Seasonal dynamics of akinetes of Anabaena flos-aquae in the bottom sediments and water column of a small Siberian reservoir

Seasonal dynamics of akinetes of Anabaena flos-aquae (Lyngb.) Breb. was studied in the sediments and the water column in profundal and littoral zones of a small Siberian reservoir. It was hypothesized that even in a shallow mixed reservoir cyanobacterial bloom initiates in the littoral zone and only then distributes throughout the water body. Two types of akinetes have been recognized: one type ensures vegetative reproduction, and the other, survival during adverse growth conditions. Seasonal dynamics of abundance of akinetes and vegetative cells was quite the same in water column in the littoral and profundal zones. However, there were differences in the seasonal dynamics of abundance of akinetes in the bottom sediments of these two areas: in the central zone the abundance increased throughout the vegetation period, whereas in the littoral zone the abundance decreased after settling of akinetes. During winter, the abundance of akinetes decreased in the sediments in both profundal and littoral zones. The explanation to this fact has not been found yet.