抄録
The net production rates of molluscan shellfishes were estimated in a high water temperature season at the tidal flat of Wakagawa estuary, and its role in nitrogen cycle was discussed. The biomass of macrobenthos was 2,648kgN and 90.0% of that was composed of 9 species of molluscan shellfish, including Ruditapes philippinarum and Crassostrea gigas. The net production rate of the dominant species was 23.9kgN · day-1 and 93.0% of that was composed of 2 species, namely, R. philippinarum and Umbonium moniliferum. Moreover, the mortality rate of the dominant species was 10.2kgN · day-1, and 86.8% of that was composed of the 2 species. The mortality rate reached 43.4% of the net production rate in the dominant species. This result indicates that one-half of production by the dominant species is consumed by carnivores, scavengers and/or decomposers. We concluded that the molluscan shellfish, particularly R. philippinarum and U. moniliferum, play important roles to link from allochthonous seston and benthic algal production to higher trophic levels, such as predators and scavengers in the tidal flat of Wakagawa estuary.
