ASSESSING BIOTIC VERSUS ABIOTIC FACTORS IN SHAPING COMMUNITY STRUCTURE IN LARGE RIVERS: RESPONSE OF ZOOPLANKTON TO ASIAN CARP IN THE ILLINOIS RIVER

Developing a fuller understanding the factors shaping aquatic community structure has implications for aquatic ecosystem restoration and management. For example, testing if abiotic variables like temperature, turbidity, or velocity are the main predictors of large rivers zooplankton assemblage abundance, biomass, and diversity. However, if biotic factors like planktivory by an invasive fish are more important, this suggests the structure and dynamics of this type of ecosystem and assemblage is more complex. To make this comparison, the influence of a suite of abiotic and biotic variables on zooplankton density, biomass, and richness over 5 years from 300 km of the Illinois River. Richness responded differently than density or biomass. For example, richness is strongly affected by Asian carp planktivory across the basin, whereas the fish only influenced biomass and density where the invaders abundance was highest. Hydrology and temperature were more important in the upper river, but only for density and biomass. This type of complex response pattern illustrates that, rather than being transient, unstructured ecosystem components, zooplankton are actually integral components of river ecosystems that respond to the mixed drivers of the riverine environment.