• Korean Journal of Environmental Biology
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• v.26 no.3
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• pp.145-158
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• 2008

To assess the source of oyster (Crassostrea gigas) and clam (Ruditapes phillippinarum), phytoplankton community structures in the water column and sediment, including the composition of phytoplankton in oyster and clam digestive organs were investigated bimonthly from December 2006 to June 2007 in the Taeahn coastal waters. During the sampling period, water temperature and salinity varied from 7 to 23$^{\circ}C$ and 34 to 35 PSU, respectively. Total phytoplankton abundances at St. O in the water column were higher than those at St. J, whereas total phytoplankton abundances at St. O in the sediment were lower. In addition, total phytoplankton abundances in the water column and sediment were observed to be relatively higher in February and April 2007. Among the diatoms, Paralia sulcata was always dominant, accounting for 41$\sim$87% of total phytoplankton, except St. J for February 2007 during the sampling period. The following phytoplankton compositions observed in the digestive organs of oyster and clam appeared: diatoms such as genus Paralia, Navicula, Melosira and Coscinodiscus, Silicoflagellate Dictyocha, dinoflagellates Prorocentrum and Dinophysis. Phytoplankton compositions observed in the digestive organs of oyster and clam corresponded relatively well with the species composition appeared in the water column and sediments of each season. A significant relationship was found between individual weight of oyster or clam and their digestive organs weight, while there was not a close correlation with total phytoplankton amount. We suggest that P. sulcata always dominated as one of important the food source of oyster and clam in the marine ranching ground of Taeahn coastal waters.