AME 23:177-186 (2001)  -  doi:10.3354/ame023177

Nitrification and denitrification in a eutrophic lake sediment bioturbated by oligochaetes

Jonas Martin Svensson1,*, Alex Enrich-Prast2, Lars Leonardson1

1Department of Ecology/Limnology, Ecology Building, University of Lund, 223 62 Lund, Sweden
2Lab. Limnologia, Depto. de Ecologia, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-540 Rio de Janeiro, Brazil

ABSTRACT: The influence on nitrification and denitrification of oligochaete Limnodrilus sp. and Tubifex tubifex bioturbation was determined in eutrophic lake sediment from the Basin of Lake Ringsjön in southern Sweden. Nitrification and denitrification activity was compared in sieved and in undisturbed sediment cores in laboratory mesocosms at 2 different concentrations of nitrate. Nitrification and total denitrification rates were positively correlated to oligochaete biomass between 0 and 4 g dry weight m-2 at both 33 and 268 μM nitrate in the inflowing water. Denitrification (dw) was relatively more stimulated by the oligochaetes at high concentrations of nitrate in the overlying water than at low nitrate concentrations. Though nitrification was enhanced by oligochaetes, this tended to reach a maximum between 3 and 5 g of oligochaete dry weight m-2. Comparison of the enhancement of denitrification by oligochaetes with other similar studies of denitrification in eutrophic sediment bioturbated by tube-dwelling chironomids indicates that at a similar biomass oligochaetes are less effective at mobilizing nitrate to deeper sediment layers. This is explained by the different ways oligochaetes and tube-dwelling chironomids bioturbate the sediment. Sieving and homogenising the sediment had no pronounced effect on rates of denitrification and nitrification compared to undisturbed sediment.

KEY WORDS: Denitrification · Nitrification · Nitrogen-cycling · Oligochaetes · Bioturbation · Lake · Eutrophic · Sediment · Sieving

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