IN SITU DETERMINATION OF BIODEPOSITION BY SUSPENSION-FEEDING BIVALVE IN SHALLOW WATERS(INTERTIDAL ZONE)

In seagrass ecosystems, bivalve filter feeders may exert a strong impact on phytoplankton and other suspended particulate matter and enhance the deposition and the fluxes of C, N, and P to benthos. In July 2012, biodeposition rates by infaunal bivalve Ruditapes philippinarum and epifaunal bivalve Crassostrea gigas were in situ measured in the Swan Lake, Rongcheng, Shandong. We designed biodeposit traps and deployed them in the intertidal zone. The biodeposit traps performed well in recording the rates of biodeposition from infaunal bivalve and epifaunal bivalve in intertidal zone in 18.8℃ of the working day. Results show that the intragroup difference was not significant, and the weight of deposits in the experiment groups were significantly higher than that of the blank control(F=58.047, P=0.000). In terms of the size, biodeposition rate of R. philippinarum in shell length of 25.0±1.5mm(flesh dry weight 0.12±0.03g) was 44.92±4.12mg/(ind·d), and that of shell length 29.8±1.3mm(flesh dry weight 0.23±0.05g) was 54.84±7.77mg/(ind·d). For C. gigas, those in shell length 98.8±14.1mm and flesh dry weight 3.94±0.66g yielded 1069.01±212.24mg/(ind·d). The biodeposition rates are similar to those previously published. As two key species, R. philippinarum and C. gigas could remove 29.9 and 15.0g/m2 of seston in eelgrass bed, respectively, by intense filtering and defecation, which could enhance pelagic-benthic interaction in local area.