Assessing the tolerance of bivalves to marine environmental degradation associated with dissolved oxygen depletion

Biodiversity is predicted to decline due to the expansion of low dissolved oxygen waters following global warming. Because most benthic species with poor mobility must tolerate low-oxygen environments, identifying species capable of surviving under these conditions and understanding their survival duration can provide a basis for assessing changes in community composition and organism conservation. In this study, a simplified experimental system using a time-lapse camera was used to assess the low-oxygen tolerance of 10 bivalve species, including rare and endangered species, inhabiting the inner part of Ariake Bay, where seasonal hypoxia occurs. Survival curves were found to be significantly shorter under low-oxygen conditions without antibiotic compared to normoxic conditions for all species, indicating the feasibility of assessing tolerance to hypoxic treatment. The duration of survival (median lethal time: LT50) varied among the 10 species under low-oxygen conditions at 25°C, offering insights into which endangered species can endure oxygen depletion. This approach is expected to provide a simple and quick assessment of tolerance to low-oxygen conditions for the conservation of marine organisms.