Do global environmental drivers' ocean acidification and warming exacerbate the effects of oil pollution on the physiological energetics of Scylla serrata?

Abstract

Global climate change-induced ocean warming and acidification have complex reverberations on the physiological functioning of marine ectotherms. The Sundarbans estuarine system has been under threat for the past few decades due to natural and anthropogenic disturbances. In recent years, petroleum products' transportation and their usage have increased manifold, which causes accidental oil spills. The mud crab (Scylla serrata) is one of the most commercially exploited species in the Sundarbans. The key objective of this study was to delineate whether rearing under global environmental drivers (ocean acidification and warming) exacerbates the effect of a local driver (oil pollution) on the physiological energetics of mud crab (Scylla serrata) from the Sundarbans estuarine system. Animals were reared separately for 30days under (a) the current climatic scenario (pH 8.1, 28°C) and (b) the predicted climate change scenario (pH 7.7, 34°C). After rearing for 30days, 50% of the animals from each treatment were exposed to 5mg L-1 of marine diesel oil for the next 24h. Physiological energetics (ingestion rate, absorption rate, respiration rate, excretion rate, and scope for growth), thermal performance, thermal critical maxima (CTmax), acclimation response ratio (ARR), Arrhenius activation energy (AAE), temperature coefficient (Q10), warming tolerance (WT), and thermal safety margin (TSM) were evaluated. Ingestion and absorption rates were significantly reduced, whereas respiration and ammonia excretion rates significantly increased in stressful treatments, resulting in a significantly lower scope for growth. A profound impact on thermal performance was also noticed, leading to a downward shift in CTmax value for stress-acclimated treatment. The present results clearly highlighted the detrimental combined effect of global climatic stressors and pollution on the physiological energetics of crabs that might potentially reduce their population and affect coastal aquaculture in forthcoming years.