[A-CG55] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

[ACG55-09] Distribution of ingestion rate of suspension feeding bivalves and primary production of microalgae on the sandy tidal flat, Japan

*Tomohiro Komorita¹, Katsumasa Yamada², Risa Takenaka¹, Shouta Ijima¹, Yoshiyuki Kuroki³, Hirokazu Yamashita³ (1.Prefectural University of Kumamoto, 2.Kumamoto University, 3.Kumamoto prefectural Fisheries Research Center)

Keywords:material circulation, estuarine tidal flat, bivalves

Food resources of the dense patches of suspension feeding bivalves, including Ruditapes philippinarum and Arcuatula senhousia, have been considered as transportation of allochthonous organic matter derived from primary producers on Midori River Tidal Flats, Japan. However, there are no direct evidence of primary production of microalgae in this area. In this study we estimated secondary production of A. senhousia in addition to primary production of phytoplankton and microphytobenthos on the Midori River Tidal Flats, and discussed quantitative evaluation of their feeding activity on the habitat. The secondary production of A. senhousia was 1.6 ± 0.7 g C m^–2 d^–1, consisting with the total primary production of phytoplankton (0.05 ± 0.04 g C m^-2 d^–1) and microphytobenthos (0.31 ± 0.33 g C m^–2 d^–1). If we assumed that growth efficiency of A. senhousia was 19%, their daily feeding rate reached 7.8 g C m^–2 d^–1, which was approximately 22 times higher than that of the primary productivity. Thus, the dense patches of A. senhousia should consume primary producers in 22 times wider area than that of their habitat area.