|Date: Tuesday, June 11, 2002|
|Location: Poster Session - VCC|
|Bergtold, M, , University of Bielefeld, Bielefeld, Germany, firstname.lastname@example.org|
|Traunspurger, W, , University of Bielefeld, Bielefeld, GERMANY, email@example.com|
|Estimating the share of production by micro-, meio-, and macrobenthos in an oligotrophic lake|
|Production measurements of the benthos in freshwater lakes are very scarce, especially for micro- and meiobenthos. However production values are important for the understanding of the turnover of nutrients in the sediment. In a one year study the abundance, biomass and production of micro- (e.g. bacteria, protozoa), meio- (e.g. nematodes) and macrobenthos (e.g. chironomids) was investigated in the profundal of oligotrophic Lake Brunnsee. The lake is situated in the southern part of Germany, has a surface area of 0.5 km2, a mean depth of 9 m and a maximum depth of 19 m.
The abundance of bacteria was measured with DAPI direct counts and ranged between 8 x 109 and 2.2 x 1010 cells ml-1. Protozoa were counted alive (Gasol 1993). Flagellate abundance varied between 18 x 103 and 147 x 103 cells ml-1 and ciliate abundance between 1 x 103 and 4.1 x 103 cells ml-1. Nematodes dominated numerically the meiobenthic organisms and ranged from 2500 to 7500 Ind. 100 cm-2. Chironomids were the prominent representatives of the macrobenthos with densities varying between 40 and 315 Ind. 100 cm-2, contributing the major part of the biomass in Lake Brunnsee.
The production of the bacteria was measured with TTI method (Bell & Ahlgren 1987). Production of protozoa and meio- macrobenthos were calculated after Finlay (1978) and Banse & Mosher (1980), respectively.
Overall production in the profundal of Lake Brunnsee was about 33 g C m-2 y-1. Bacteria produced 66 % of that carbon, protozoa 20%, macrobenthos 9%, and meiobenthos 5%.
The seasonal dynamics of the benthic organisms in the profundal of Lake Brunnsee are presented and compared with the production of other freshwater systems.