Physiological responses of whitespotted bamboo shark (Chiloscyllium plagiosum) to high CO2 levels

Sharks have been roaming the planet for 400 million years and are vital elements for the health of our oceans. Due to occurring changes in the food-web and anthropogenic pressure from fishing and habitat degradation, sharks populations are now declining sharply. Ocean acidification, caused by continuous release of carbon dioxide (CO2) to the atmosphere, may represent an additional threat. Among other effects, it may cause physiological disturbances in the organisms and threaten marine ecosystems as we know them, especially the most vulnerable life stages. Hence, the present study focus on the effects that ocean acidification may have on the fitness, metabolism and swimming performance of juvenile whitespotted bamboo sharks (Chiloscyllium plagiosum). After hatching, sharks were placed in either control (pCO2 ~ 400 μatm, pH = 8.0) or high CO2 (pCO2 ~ 900 μatm, pH = 7.7) conditions, according to the pH levels expected by the end of the century. After an exposure of 45 days, several ecologically important traits were tested, namely their fitness [(i) Fulton condition], metabolic capacity [(i) routine metabolic rate (RMR), (ii) maximum metabolic rate (MMR), (iii) aerobic scope (AS)] and swimming performance [(i) maximum reached velocity, (ii) percentage of time swimming, (iii) number of bursts and (vi) pre and (vii) post-stress ventilation rates]. No changes were observed in their fitness, metabolism and the majority of the swimming performance end-points. Nevertheless, regarding the swimming performance, there was a decrease of the duration of swimming events and a decrease in the post-swimming ventilation rates. Over the past years, these cartilaginous fish have been coping with oscillations in the seawater chemistry and thus appear to be resilient to OA. However, this species’ conservation status is of concern, assessed as Near Threatened, and even the sub-lethal effects observed in this study may potentially reduce the organism’s overall fitness and ultimately impact population dynamics.

Pinto E. F. C., Physiological responses of whitespotted bamboo shark (Chiloscyllium plagiosum) to high CO2 levels. MSc thesis, Universidade de Lisboa, 32 p. Thesis.

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