HR: 1330h
AN: NB33N-06    [Abstracts]
TI: Does Nutrient Enrichment Alter the Response of Stream Macroinvertebrates to Disturbance?
AU: * Gafner, K
EM: kgafner@student.ethz.ch
AF: EAWAG/ETHZ, Department of Limnology, Ueberlandstrasse 133, Duebendorf, 8600 Switzerland
AU: Robinson, C T
EM: robinson@eawag.ch
AF: EAWAG/ETHZ, Department of Limnology, Ueberlandstrasse 133, Duebendorf, 8600 Switzerland
AB: We examined the influence of nutrient enrichment on the response of benthic macroinvertebrates to disturbance in springbrooks of an alpine floodplain. Individual stones in three different springs were physically disturbed at frequencies of 0, 4, 8 and 16 days, and then collected on day 32. In another experiment, nutrients (slow-release fertilizer pellets) were added to one of two streams, and stones in both treated as in the first experiment. In both experiments, stones were analyzed for periphyton biomass, total invertebrate density, and the density and relative abundance of four common families: Baetidae, Nemouridae, Chironomidae, and Simuliidae. N, P, and C were analyzed for periphyton, benthic sediments and invertebrates in the 2nd experiment to test for stoichiometric changes resulting from nutrient enrichment. In the 1st experiment, disturbance affected the relative abundance of the four families. Fertilization changed the stoichiometry of periphyton, invertebrates and sediments and altered macroinvertebrate assemblages. Here, the effect of disturbance differed between the two streams, and the non-fertilized stream displayed a similar disturbance response pattern by macroinvertebrates as in the 1st experiment. These results suggest that nutrient enrichment alters the effects of physical disturbance on macroinvertebrates by changing food resource stoichiometry and shifting macroinvertebrate assemblage structure.
DE: 1899 General or miscellaneous
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly