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2 Polish Journal of Ecology

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Biomass distribution and dynamics and food web relations in psammon community of a eutrophic lake

Kalinowska K., Ejsmont-Karabin J., Gorelysheva Z., Rybak J.

Polish Journal of Ecology

2012

Vol. 60, nr 3

443-453

Organisms living in submerged sand along the shore and below the water's edge in freshwater lake beaches create community called hydropsammon (see Fig. 1 in Preface). Trophic relations between psammon food web components are essential in energy flow, nutrient cycling and functioning of aquatic environments. The seasonal changes in algal, bacterial, nanoflagellate, ciliate, rotifer and crustacean biomass were investigated in hydroarenal (submerged sand) of the eutrophic Lake Mikołajskie (Poland). Sampling cores were taken once or twice a month since April till October 2005 from three layers: adjacent water layer (AWL), layer of water and sand from the transitory level (EPIH - epihydroarenal) and slice of sand (ENDOH . endohydroarenal). The mean annual phytopsammon biomass was extremely high in all microlayers. Bacterial biomass was the highest in the ENDOH. Biomass of nanoflagellates was 4 to 8 times lower than that of bacteria and was the highest in the AWL. The highest mean annual biomass of ciliates was recorded in the EPIH, whereas rotifers dominated in the ENDOH. In contrast, average biomass of Crustacea was the highest in the AWL. Crustaceans dominated heterotrophic biomass in the AWL and EPIH (92 and 54% of the total biomass, respectively) whereas bacteria definitely prevailed in the ENDOH (57%). The ratios of autotrophic to heterotrophic biomass and prey to predator biomass as well as trophic relations between the studied groups of psammon organisms differed clearly among microlayers. The AWL was characterised by the lowest autotrophic/heterotrophic and predator/prey biomass ratios (about 2) and significant positive correlations between nanoflagellates and ciliates as well as between protists and both rotifers and copepods. The highest autotrophic/heterotrophic and predator/prey biomass ratio (14 and 40, respectively) and lack of correlations was found in the ENDOH. These results may suggest that the pressure of consumers was weaker in the hydroarenal layers than in the AWL. In addition, it seems that psammon ciliates, rotifers and crustaceans inhabiting the ENDOH were probably limited by factors other than food availability. In contrast to the pelagic ecosystems, autotrophic biomass exceeded heterotrophic biomass, especially in the ENDOH.

Daily changes of the vertical micro-distribution of Rotifera in lake psammolittoral

Ejsmont-Karabin J.

Polish Journal of Ecology

2008

Vol. 56, nr 4

717-722

Studies were conducted in littoral sand deposits of a eutrophic, deep lake (Lake Mikołajskie, Masurian Lakeland, Poland) in aim to test the hypothesis that epihydroarenal (the most upper layer of sand deposits) may play a role of a refuge from visual predators for rotifers from adjacent water layer. However, a comparison of the daily vertical distribution of the rotifer community structure and densities in microlayers of the lake psammolittoral, i.e. adjacent water layer (5.0-0.0 cm), epihydroarenal (0-0.5 cm) and three microlayers of endohydroarenal (0.5-1.0 cm, 1.0-1.5 cm and 1.5-2.0 cm) revealed a lack of up-and-down vertical migrations of the animals. During day and night hours, both on 5/6 and 11/12 July, rotifers were concentrated in epihydroarenal. In all cases 64 to 85% of rotifer community inhabited this layer, whereas up to 4% occurred in adjacent water layer. Large and permanently renewed food resources (algae and bacteria) in the most upper layer of sand deposits form a very thin layer that can be called "a canteen". This may explain permanent concentration of rotifers in the layer.