Population dynamics of a hypoxia-tolerant bivalve: A comparison of two sites in the inner part of Ariake Bay, Japan

Hypoxia-tolerant bivalve populations could be a key component of ecosystem function because of their predominance in hypoxic environments. In this study, we conducted field surveys at two sites to ehicidate the biological traits of the hypoxia-tolerant bivalve Veremolpa micra. We detected new settlements at both sites during summer. I More highly reduced conditions in the surface sediment were recorded at Site-A than at Site-B in August 2013. Following this hypoxic event, shell growth of V micra at Site-A decelerated, whereas that at Site-B increased. The population density after recovery from the hypoxic event decreased more at Site-B than at Site-A. Body size exhibited very little growth at both sites during the fall and winter, but there was rapid growth during the subsequent spring and summer, 0 with sexual maturity being reached in early summer. Our findings demonstrated that the growth rates and survival patterns of the hypoxia-tolerant bivalve populations differed between sites with different degrees of sediment reduction. To understand the biological traits of hypoxia-tolerant bivalve species, it is necessary to consider and evaluate spatial differences in hypoxic stress at the local site level.