PARENT SESSION
Oral Session # 82: Aquatic Ecology: Freshwater.
Presiding: A Soja
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 200.
Relative effects of climate and biotic interactions on plankton dynamics.
Hampton, Stephanie*,1, Schindler, Daniel1, 1 University of Washington, Seattle, WA
ABSTRACT- Aquatic ecosystems throughout the world are subject to changing climate, human alterations of food webs and nutrient cycles, and introductions of exotic species. Understanding the ecological effects of these human perturbations is somewhat limited because they are usually confounded in time. The probability that population dynamics are affected through both direct and indirect pathways further complicates the prediction of response to anthropogenic disturbance. Development of new multivariate autoregressive models (MAR) provides a new set of tools for understanding complex ecological dynamics in time series data. The long-term limnological data set from Lake Washington provides the opportunity to study plankton community responses to several anthropogenic disturbances as well as long-term climatic changes. Over the last four decades, lake temperature has clearly increased, nutrient loading has dramatically decreased, and the food web has been altered. To discern the effects of multiple factors on multiple interacting species, we used MARs to determine the relative importance of abiotic drivers and biotic relationships in altering species abundance. Nutrient loading reduction directly altered phytoplankton characteristics by reducing total abundance of cyanobacteria. At the same time, anthropogenic alteration of the fish community reduced predation on zooplankton grazers by Neomysis, a voracious invertebrate predator. Together these abiotic and biotic perturbations overrode climatic effects in shifting dominance of the grazer community to Daphnia, which produced further changes in phytoplankton characteristics as well as phenological changes for competing grazers such as Diaphanosoma, Bosmina, and Conochilus.
Key words: competition, predator-prey, eutrophication, global warming