Incorporation of Cochlodinium bloom-derived organic matter into a temperate subtidal macrobenthic food web as traced by stable isotopes.

Harmful algal blooms involving the dinoflagellate Cochlodinium polykrikoides occur every summer off the Korean peninsula's central southern coast. To determine whether Cochlodinium bloom-derived organic carbon is incorporated into the subtidal macrobenthic food web, we compared the δ13C and δ15N values of suspended particulate organic matter (SPOM) and sedimentary organic matter, and macrobenthic consumers between bloom and non-bloom seasons. Chemotaxonomic analysis revealed the presence of Cochlodinium blooms in summer and a predominance of diatoms in autumn. Both the δ13C and δ15N values of SPOM were higher in the bloom than in the non-bloom seasons. Such temporal shifts in the δ13C and δ15N values were also observed for most macrobenthic consumers collected in both seasons. Consistent temporal isotopic shifts in SPOM and macrobenthos revealed that the Cochlodinium bloom-derived carbon was incorporated into the coastal benthic food web, resulting from its increasing availability during blooms.

Organic and inorganic matter increase related to eutrophication in Gamak Bay, South Korea.

Water quality the carbon isotope ratio of suspended particulate organic matter (POM), and limiting nutrients were investigated at seven surface and bottom seawater stations in Gamak Bay South Korea, to evaluate the effectiveness of counter-measures to organic matter increase. The increase in surface water COD in Gamak Bay appear to be the result of phytoplankton growth, which is consistently limited by nitrogen (N) or phosphorous (P), but not by silicon (Si). High chlorophyll a concentrations seem to be caused by freshwater inputs of N and P associated with wastewaterin the northern and northeastern portions of the Bay, and by the inflow of NH4-N and P associated with the digestion of organic matter from the bottom layer in western areas. To regulate the increase of organic matter in Gamak Bay, controlling phytoplankton growth, particularly by regulating the input of N or P, may be more important than controlling the input of terrestrial organic matter.