Some coral species display resilience to the effects of ocean warming and acidification due to climate change, reports a study of three types of coral in Hawaii published in Scientific Reports. These findings provide insight into the possible capacity for some corals to survive and cope with changing ocean conditions.
Coral reefs across the globe face threats from increasing ocean temperatures and acidification due to climate change, which puts significant stress on coral health and can lead to mass coral bleaching.
Rowan McLachlan and colleagues collected 66 samples from three coral species across four reef sites in Hawaii between 29 August and 11 November 2015. The three species were Montipora capitata (a branching and plating stony coral), Porites compressa (a branching species known as finger coral), and Porites lobata (or lobe coral, a boulder-shaped species). The samples were placed in seawater tanks with four different conditions: a control tank with current ocean conditions, an ocean acidification scenario (-0.2 pH units), an ocean warming scenario (+2 °C), and a combined acidification and warming scenario. The coral samples were maintained under these conditions for 22 months.
The authors found coral survival was influenced by temperature, with only 61% of coral samples surviving warmer conditions compared to 92% in the control tank. Across the three climate change conditions, M. capitata had lower survival than P. compressa (67% vs 83% survival). P. compressa was also more resilient in the combined warming and acidification condition compared to M. capitata and P. lobata, with 71% of samples surviving compared to 46% and 56% respectively. The authors suggest that, unlike under the control conditions, many M. capitata individuals were unable to acquire enough energy to survive under the combined climate change conditions. This could explain its higher mortality rates compared to P. compressa, which, in contrast, was able to acquire more than enough energy in future ocean conditions. There were few physiological differences between surviving P. lobata corals under control or future ocean conditions.
The authors suggest that the resilience of Porites species of corals to temperature and acidification, and their role in in reef building, provide hope that some reef ecosystems may be maintained despite changing ocean conditions.
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