| |
Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Periphyton
THE EFFECTS OF NUTRIENTS AND GRAZERS ON PERIPHYTON IN MISSION CREEK, CALIFORNIA.
L.B. Busse and S.D. Cooper. Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara CA 93106
The combined effects of top-down and bottom-up factors are often more important in determining periphyton biomass and species composition than either factor alone. The most promising approach in delineating the simultaneous effects of top-down and bottom-up processes on periphyton communities is to conduct experiments in which both resources and consumers are manipulated. We studied the effects of manipulations of nutrients and grazers on periphyton biomass and species composition in experimental channels and pools placed in different habitats (riffles and pools) and conducted during different seasons (summer and fall) in Mission Creek, California. Our results showed that nutrient effects on algal biomass and species composition were greater in summer than in fall, and that grazer impacts on algae were able to override nutrient effects in the fall. We conclude that the magnitudes and relative importance of top-down and bottom-up controls differ from season to season.
|
|
