Sources and spatial and temporal characteristics of organic carbon in two large reservoirs with contrasting hydrologic characteristics

We investigated the sources, fluxes, and spatial and temporal distribution of organic carbon in two large reservoirs in Korea having different trophic and hydrologic features. In Lake Paldang (river‐type reservoir) most of the organic carbon comes from allochthonous sources (88%), while in Lake Chungju (lake‐type reservoir) the allochthonous load contributed 52% (48% autochthonous). Strong correlations were found between the amount and contribution of allochthonous and autochthonous organic carbon and hydrologic parameters in Lake Paldang but not in Lake Chungju. The spatiotemporal fluctuation patterns of C/N ratios of particulate organic matter, chlorophyll a/particulate organic carbon values, and specific ultraviolet absorption of dissolved organic carbon were different, indicating differences in state and source of organic carbon in the two reservoirs. Our results indicate that meteorologic and hydrologic controls directly determine the state of lacustrine organic carbon in Lake Paldang, whereas autochthonous production and in situ transformation may play important roles in determining the state of lacustrine organic carbon in Lake Chungju.