Biogeochemical influences on the carbon isotope signatures of Lake Ontario biota

Abstract

Particulate organic matter (POM), zooplankton, and benthic invertebrates were sampled seasonally at a midlake and east basin site in Lake Ontario. The δ13C values of POM samples were compared with measurements of chlorophyll a concentrations, areal rates of primary productivity, concentrations of dissolved free CO2 (CO2(aq)), and the δ13C of zooplankton and benthic invertebrates. The δ13C of POM was significantly correlated with the concentration of CO2(aq) at the east basin site. No correlation was found between chlorophyll a concentrations, areal rates of primary productivity, and the δ13C of POM. The δ13C of zooplankton was not always similar to the δ13C of the POM fraction collected, indicative of the complexity of food web interactions within the lower trophic levels. The δ13C of benthic invertebrates feeding on the sediment surface was similar to that of POM produced prior to stratification, indicating the importance of the spring bloom as a food source for benthic primary consumers.