title: The effects of nematodes on bacterial activity and abundance in a freshwater sediment.
abstract: The effects of natural nematode communities on bacterial activity and abundance were investigated in a microcosm study. Nematodes were added at different densities to a freshwater sediment and bacterial parameters were measured after 1, 5, 9, and 17 days. Significant effects of nematode density on bacterial activity were noted on day 5. No long-term changes in bacterial activity were recorded. Bacterial abundance displayed an overall decrease in both treatments and controls. In a second experiment, the effect of nematode feeding-type on bacterial activity was studied. Microcosms were incubated with 100 individuals of a fungus-feeding (Aphelenchus avenae) or a bacteria-feeding nematode species (Caenorhabditis elegans) respectively, and bacterial activity was determined after 0, 1, 2, 4, and 7 days. Significant time and feeding-type effects were found, with consistently higher bacterial activity estimates in treatments with bacteria-feeding nematodes. These results suggest that grazing affects bacterial activity, and indicate that grazing by nematodes may be more important in stimulating bacterial activity than bioturbation or excretion. Combining these results, we conclude that natural nematode communities may have an impact on bacterial activity, and that the magnitude of this impact depends on the proportion of actively feeding bactivores within the community.
authors.affiliation: Zoological Institute, University of Munich, Luisenstrasse 14, D-80333 Munich, Germany Fax: (+49) 89-5902-461; e-mail: traunsp@zi.biologie.uni-muenchen.de, , , , , , DE.
authors.forename: Walter
authors.initials: W
authors.lastname: Traunspurger
authors.affiliation: Zoological Institute, University of Munich, Luisenstrasse 14, D-80333 Munich, Germany Fax: (+49) 89-5902-461; e-mail: traunsp@zi.biologie.uni-muenchen.de, , , , , , DE.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bergtold
authors.affiliation: Institute of Limnology, Uppsala University, Norbyvägen 20, S-756 32 Uppsala, Sweden, , , , , , SE.
authors.forename: Willem
authors.initials: W
authors.lastname: Goedkoop
keywords: Bacterial activity; Freshwater sediment; Key words Nematoda; Microcosms