FROM BOTTLES TO LAKES: ECOSYSTEM MODEL DEVELOPMENT BY CONVERTING MICROCOSM-DERIVED RATES INTO LAKE-RELEVANT EFFECTS

Jessica King, Nicole Kelver, Tim Sellers, Center of Aquatic Research, Keuka College, Keuka Park, NY 14478

Phytoplankton (microscopic suspended algae) are the base of aquatic food webs in lake and oceanic ecosystems. Accordingly, changes in their population sizes and species structure will cascade and can affect entire ecosystems. Therefore, understanding how and why phytoplankton change is critical to understanding and protecting aquatic ecosystems. Microcosm experiments are a valuable tool in phytoplankton ecology research, as they can provide insight into factors affecting growth (limiting factors), rates of growth and interaction effects. These factors and growth rates can then be incorporated into mathematical models to simulate and investigate plankton dynamics and ecosystems effects from watershed processes (e.g., nutrient runoff). However, in order to use microcosm-derived algal growth rates, microcosm ‘bottle effects' must be accounted for and calibrated to lake-relevant rates. Our research attempts to identify the biological and physical factors resulting in altered growth rates from ‘bottle effects'. By running multiple phytoplankton growth experiments in varying microcosm volume and geometries, we have deciphered the causes for the effects and derived biologically-relevant mathematical functions used to convert lab-based growth rates into lake-relevant rates. Our studies suggest that heterotrophic bacteria associated with the wetted surface area of microcosms compete with phytoplankton By quantifying the specific bottle geometry (e.g., bottle SA:V ratios) biological competition interference effects can be mathematically removed. The new competition-corrected values can now be used in ecosystem-level model development.

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