Temperature mediated hypoxia tolerance in a Northeastern Pacific Crab

Abstract

Hypoxic events are increasing in frequency and are often linked to mass mortalities, habitat compression, and re-distribution of marine species. While organismal responses to hypoxia are a growing area of research, few studies have investigated hypoxia tolerances in the Pacific Ocean which experiences significantly lower dissolved oxygen levels than other ocean basins. In this study, I evaluated the hypoxia tolerance of graceful crab (Metacarcinus gracilis), native to the Northeastern Pacific Ocean. Lab-based respirometry experiments were used to determine the basal metabolic rate (BMR) and critical oxygen level (O2crit) of this species and were combined with field distribution and oceanographic data to calculate the metabolic index across its geographic range. These results show that, near in situ temperatures (8 C), average BMR was 4.59 mg/L/g/hr and increased to 9.89 mg/L/g/hr. To compensate for this uptick in metabolic oxygen demand, O2crit also increased from 0.48 to 1.14 mg/L. From Alaska through British Columbia to Southern California, the metabolic index of M. gracilis ranges from 11.7 to 18.4. These results indicate that this crab is tolerant of fluctuating oxygen and has lower than average O2crit for the ocean basin. In order to establish realistic predictions of biological and ecological consequences of marine deoxygenation, further studies should integrate metabolic characteristics with in situ distribution and condition data to evaluate the hypoxia tolerance of marine communities and ecosystems.