Variation in carbon and nitrogen stable isotopes in POM and zooplankton in a deep reservoir and relationship to hydrological characteristics

We investigated the carbon and nitrogen stable isotope composition of particulate organic matter (POM) and zooplankton to understand the effects of highly variable hydrologic inputs with the onset of the summer monsoon season in Lake Soyang, Korea. The main characteristic separating pre-monsoon and post-monsoon seasons in Lake Soyang is the dramatic difference in hydrologic inflow. Pre-monsoon δ13C-POM (range −32.4 to −21.8‰) was lower than post-monsoon δ13C-POM (range −25.5 to −19.9‰). Epilimnetic δ13C-POM was higher post-monsoon compared to pre-monsoon, except in 2007. In the metalimnion, pre-monsoon δ13C-POM varied among years, while the variation in δ13C-POM post-monsoon was small and was related to the inflow of organic matter during summer monsoon storms. δ13C-zooplankton was lower post-monsoon (range −31.9 to −24.4‰) compared to pre-monsoon (range −19.4 to −17.7 ‰), while δ15N-zooplankton showed the opposite pattern (pre- and post-monsoon average 6.6 ± 2.0‰ and 4.3 ± 1.5‰, respectively). In Lake So...