The efficiency of mitigation on Cochlodinium bloom by red mud

초록

To investigate the effect of red mud on the mitigation of Cochlodinium blooms and the impact of other plankton, we carried out field experiment and laboratory experiments under the blooming conditions of Cochlodinium in the southern coastal watrrs of Korea on August 2007. Four hundred g m-2 red mud was sprayed directly on the sea surface for field experiment and the laboratory tests was conducted to examine how red mud treatment affects the precipitation and motility of Cochlodinium. The red mud removed the 72% of Cochlodinium population after 1O minutes of spraying in the sea surface in the field experiment. Cochlodinium cell number decreased 76% in the motility experiment at l0 min after addition of 400 mg l-1 red mud in laboratory experiment. There was 83% of sedimentation at the surfuce layer in the first l0 min and the cell nurnber at the 40cm layer also decreaseds significantly after 30 min. Theser esults indicate that the 400 mg l-1 of red mud has high efficiency in the mitigation of Cochlodinium HAB Also, the effects of red mud on the heterotrophic bacteria and ciliates were studied in laboratory experiment. Heterotrophic bacteria abundance was 1.6 times higher than those of control experiment after addition of 40Omgl-1 red mud at l6h later. The cell number of dominant ciliate Strombidium sp. was similar with those of control, experiment after addition of 400mg l-1 red mud at l6h later. Red mud might be safety as mitigation material in the pelagic ecosystem.