Effects of the summer monsoon on the distribution and loading of organic carbon in a deep reservoir, Lake Soyang, Korea

Seasonal and vertical patterns of organic carbon concentration, and an orga nic carbon budget were studied in a deep reservoir in Korea. Dissolved orga nic carbon (DOC) and particulate organic carbon (POC) were measured in the river inflow and at the dam. Autochthonous production of carbon was estimat ed from phytoplankton primary productivity. Variations in POC were greater than for DOG, reflecting pronounced changes in algal biomass during the stu dy period. Before the monsoon, in spring and early summer, DOC concentratio ns consistently were low (ca. 1.5 mg l(-1)). Heavy rains associated with th e summer monsoon had substantial impacts on the lake's carbon budget. Turbi d storm runoff supplied large quantities of nutrients and organic carbon to the metalimnion. Some of these substances were advected into the epilimnio n, and may have contributed to a seasonal increase in primary productivity. Although annual rates of carbon supply from allochthonous and autochthonou s sources were similar, the autochthonous carbon appears to be a more impor tant energy source in the lake because most aliochthonous carbon was discha rged from the dam without affecting the epilimnion. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.