Factors Influencing the Vertical Distribution of Nematodes in Sediments

ABSTRACT

The effects of oxygenation of sediment and the presence of macrobenthic organisms (gammarids, tubificids, and chironomid larvae) on the vertical distribution and species segregation of nematodes were studied in laboratory microcosms with freshwater sediment. The abundance of nematodes was positively affected by oxygenation, particularly in the deep sediment layers. Small nematodes increased in the deeper layers of oxygenated treatment. Macrobenthic animals did not influence abundance or vertical distribution of nematodes but had an impact on nematode community structure. The families Tobrilidae and Monhysteridae dominated the community. In the control treatments the monhysterids were abundant, whereas the importance of tobrilids increased in the treatments with macrobenthic animals.