PARENT SESSION
Oral Session #89: Biodiversity and Ecosystem Function III.
Presiding: R. Washington-Allen
Thursday, August 8. 1:00 PM to 3:45 PM. Coconino Meeting Room, TCC.
Effects of algal and herbivore diversity on ecosystem properties in aquatic microcosms.
FOX, JEREMY*,1, 1 NERC CENTRE FOR POPULATION BIOLOGY, ASCOT, BERKSHIRE, UK
ABSTRACT- A complete understanding of the relationship between biodiversity and ecosystem function will require consideration of multiple trophic levels. I assembled communities of bacteria, algae, and herbivorous protists in laboratory microcosms to examine the joint effects of algal and herbivore diversity on several ecosystem properties. The experiment crossed two algal diversity treatments (1 or 8 species) with three herbivore diversity treatments (0, 1, or 3 species). Single-species treatments comprised monocultures of every species used in more diverse treatments, for a total of 45 unique communities, each replicated twice. The experiment lasted 2 months, equal to dozens of generations of the study organisms. Mean total algal biomass at the end of the experiment increased with initial algal diversity in both the presence and absence of herbivores, largely due to a selection effect for more competitive algae. Herbivores reduced the strength of the selection effect by grazing competitive algae, but the magnitude of the reduction did not vary between herbivore diversity treatments. Mean total herbivore biomass increased with increasing algal diversity due to a selection effect for edible algae, and increased with herbivore diversity due to niche complementarity among herbivores. Algal and herbivore community composition also affected bacterial density. The results are broadly consistent with predictions of simple mechanistic food web models.
KEY WORDS: microcosms, biodiversity, ecosystem function, protists