Stable carbon isotope signatures of zooplankton in some reservoirs in Korea

초록

Dissolved organic carbon (DOC) concentrations and zooplankton and particulate organic matter (POM) δ13C values were measured in five reservoirs in Korea. Zooplankton δ13C and POM δ13C showed large range from -33‰ to -22‰ and a significant difference among the reservoirs. One eutrophic reservoir, Lake Masan, showed unique characteristics with the highest zooplankton density, the highest δ13C, and the highest DOC. Zooplankton δ13C was similar to POM δ13C, implying that zooplankton occupies substantial portion of POM or that zooplankton isotopic composition is related to selective grazing and assimilation of food sources from bulk POM. Except Lake Masan zooplankton δ13C values were negatively correlated to DOC concentration in four reservoirs with mostly forest land use. This pattern can be probably attributed to intensive agricultural land use in the watershed of Lake Masan compared to the mostly forest land use in the other watersheds. Understanding the relationship between zooplankton δ13C values and the origin of organic matter associated with watershed characteristics will be valuable to better understand trophic relationships in reservoirs in the summer monsoon region.

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