Impact of ocean acidification and warming on the early ontogeny of a tropical shark

Sharks occupy high trophic levels in marine habitats and play a key role in the structure, function and health of marine ecosystems. Sharks are also one of the most threatened groups of marine animals worldwide, mostly due to overfishing and habitat degradation or loss. Although sharks have evolved to fill many ecological niches across a wide range of habitats, they have limited capability to rapidly adapt to human-induced changes in their environments. Until now, ocean acidification was not considered as a direct climate-related threat to elasmobranchs. In the present study we show, for the first time, that a long-term acclimation process of a tropical shark (Chiloscyllium punctatum) to the projected scenarios of ocean acidification (ΔpH 0.5) and warming (+4 °C) for 2100, elicited significant deleterious effects on juvenile shark’s fitness and survival. During embryogenesis, none of the parameters measured (survival, development time, yolk consumption and specific growth rate) was significantly affected by hypercapnia, with the exception of routine metabolic rates at intermediate and pre-hatching stages. However, temperature warming exposure significantly affected the embryos. The effects caused by environmental conditions, experienced throughout embryogenesis, seem to have been transmitted to the next developmental stages (juvenile sharks). This carry-over effect may play a critical role in the reductions in the fitness of sharks under climate change. Thus, it is critical to directly assess the risk and vulnerability of sharks to ocean acidification and global warming so that managers and policy-makers can proactively target the most endangered shark species.

Pegado M. R., 2013. Impact of ocean acidification and warming on the early ontogeny of a tropical shark. (MSc thesis, University of Lisbon, 42 pp. Thesis.

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