Small-scale variation in feeding environments for the Manila clam Ruditapes philippinarum in a tidal flat in Tokyo Bay [Japan]
2009
Watanabe, S.(Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki) | Katayama, S. | Kodama, M. | Cho, N. | Nakata, K. | Fukuda, M.
The relative contribution of particulate organic matters (POMs) in water column and sediment as a food source for the Manila clam, Ruditapes philippinarum, was studied using carbon and nitrogen stable isotopic method (delta sup(13)C and delta sup(15)N) in a tidal flat at Seaside Park, Yokohama, Japan. Comparisons of delta sup(13)C and delta sup(15)N among R. philippinarum and POMs in surface water, bottom water, and sediment surface indicated that R. philippinarum larger than 5 mm shell length (SL) mainly assimilated benthic POM, and individuals smaller than 5 mm SL assimilated benthic and pelagic POM. Continuous measurements of chlorophyll concentrations in the bottom water revealed tide-driven resuspension of the benthic phytopigments. R. philippinarum showed differences in delta sup(13)C and delta sup(15)N along an inshore-offshore transect, indicating small-scale spatial differences in POM provision in the tidal flat. These findings suggest that POM in the bottom water, supposedly inhaled by R. philippinarum, is a mixture of a larger proportion of resuspended benthic POM and a smaller proportion of pelagic POM, and that the mixing ratio of the POMs may be affected by the hydrodynamics of flooding water associated with tidal flat topography.
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