Accumulation of organic matter within a muddy carpet created by the Asian date mussel, Arcuatula senhousia, on the Midori River tidal flats, Japan

Abstract

The Asian date mussel (Arcuatula senhousia) dominates macrobenthic communities on the Midori River tidal flats on the island of Kyushu, the southernmost of Japan’s main islands. They form dense patches and create mats on the sediment surface. We conducted field surveys between May 2014 and April 2015 to assess the vertical distribution of sedimentary conditions (depth 0–12 cm) and determined the seasonal variation in density, biomass, and secondary production of A. senhousia on the tidal flats. Arcuatula senhousia density and biomass reached a maximum of 80,800 individuals per square meter (ind. m⁻²) in September and 4,988 g wet weight (WW) m⁻² in August, respectively. We defined a sediment layer with >10 mg dry weight (DW) of byssus as the byssus layer. From May to November, the integrated standing stock of sedimentary nitrogen (N) within the byssus layer derived from A. senhousia (150.7 g N m⁻² 7 months⁻¹) was as high as the secondary production of A. senhousia (161.8 g N m⁻² year⁻¹). Thus, this study clearly indicates that accumulated sedimentary nitrogen within the byssus layer plays a considerable role in nutrient cycling in the Midori River tidal flats.