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 δ 13 C values of POM samples were compared with measurements of chlorophyll a concentrations, areal rates of primary productivity, concentrations of dissolved free CO 2 (CO 2(aq) ), and the δ 13 C of zooplankton and benthic invertebrates. The δ 13 C of POM was significantly correlated with the concentration of CO 2(aq) at the east basin site. No correlation was found between chlorophyll a concentrations, areal rates of primary productivity, and the δ 13 C of POM. The δ 13 C of zooplankton was not always similar to the δ 13 C of the POM fraction collected, indicative of the complexity of food web interactions within the lower trophic levels. The δ 13 C 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.