Understanding Carbon Sources and Energy Flow in Ponds of Different Trophic Status

Session: Poster Session

Meghan Brown, Hobart and William Smith Colleges, [email protected]
Penelope Murphy, Hobart and William Smith Colleges, [email protected]

Abstract

Ponds are hotspots for diversity that provide important ecosystem services. They also serve as model systems for investigating food-web dynamics that are relevant to larger lake systems. We studied two neighboring ponds that differ in their trophic status—one is eutrophic, the other oligotrophic—despite their shared terrestrial surrounding, management strategy, and human-constructed, mid-century origin. We investigated primary productivity and food-web structure using carbon and nitrogen isotopes to test the hypothesis that the food webs of these ponds vary in their utilization of carbon sources (e.g., terrestrial-based detritus, macrophytes, periphyton, phytoplankton) and how energy flowed into primary, secondary, and tertiary consumers.  As expected, the consumer communities of both ponds exploited terrestrial-based carbon but differed in the dominant source of autochthonous carbon. The oligotrophic pond incorporated more benthic carbon sources into its food web while the more productive pond was skewed to pelagic carbon sources, findings which correlate with the observed primary production in these regions of the ponds. There were also differences at higher trophic positions, including the types of fish and their diets. This study adds to the growing body of work dedicated to understanding the factors that dictate productivity and energy flow of freshwater systems.