SS4.13 Water Quality of Lakes, Rivers and Coastal Zones
Date: Thursday, June 13, 2002
Time: 12:00:00 PM
Location: Carson B
 
KleppelGS, University at Albany,SUNY, Albany, NY, USA, gkleppel@csc.albany.edu
Hazzard, S, E, University at Albany, SUNY, Albany, NY, USA, sehazzard@hotmail.com
 
FUNCTIONAL RESPONSES TO CHANGING BIODIVERSITY AND HUMAN PERTURBATION IN PLANKTONIC ECOSYSTEMS
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Although it is widely held that ecosystem function (F=process, performance) varies with structure (S=biodiversity), the nature of the relationship is contentious. Thus, while human disruption of habitats is altering S, F remains unpredictable. We tested the hypotheses that (i) F varies systematically with S and (ii) F is affected by perturbation in estuarine planktonic ecosystems. Phytoplankton was enumerated microscopically, biomass (Cp) being determined from cell-volumes or chlorophyll. Acartia tonsa (Copepoda) was used as a community analog for the zooplankton (Cz). Biological rates - i.e., phyto- and zooplankton growth (Gp, Gz), ingestion (I), egg production (EP) -- were measured with "bottle experiments". Ecological efficiencies were estimated as ratios of biomasses and rates: Cz/Cp, Gz/Gp, EP/I. Biomass and biological rates were poorly correlated with S. Ecological efficiencies gave improved correlations (r2 ranged from 0.37-0.80), though the sign of the relationship varied. Biomass quadrupled and rates nearly doubled with estuarine perturbation, but ecological efficiencies in perturbed estuaries declined by 50-75 percent. Thus, the variables used to describe F affect both the perceived relationship with S and the ecosystem response to human encroachment.