According to a study involving three types of coral in Hawaii, a few coral species exhibit resilience to the effects of ocean warming and acidification caused by climate change.
The study has been reported in the Scientific Reports journal.
The observations offer insight into the possible capacity for a few coral species to survive and cope with altering ocean conditions.
As a result of climate change, coral reefs experience threats from increasing ocean temperatures and acidification. This places considerable stress on coral health and can also result in mass coral bleaching.
Around 66 samples were gathered by Rowan McLachlan and collaborators from three coral species across four reef sites in Hawaii between August 29th and November 11th in 2015. The three species were Montipora capitata (a branching and plating stony coral), Porites lobata (or lobe coral, a boulder-shaped species) and Porites compressa (a branching species called finger coral).
In four different conditions, the samples were placed in seawater tanks: a control tank with current ocean conditions, an ocean acidification scenario (–0.2 pH units), an ocean warming scenario (+2 °C) and an integrated acidification and warming scenario. The coral samples were retained under these conditions for around 22 months.
The authors discovered that coral survival was impacted by temperature, with just 61% of coral samples surviving in warmer conditions compared to 92% in the control tank. Throughout the three climate change conditions, M. capitata exhibited lower survival compared to P. compressa (67% vs 83% survival).
Furthermore, P. compressa was more flexible in the integrated warming and acidification condition compared to M. capitata and P. lobata, with 71% of samples living compared to 46% and 56%, respectively.
The authors indicate that, unlike under the control conditions, several M. capitata was not capable of obtaining sufficient energy to survive under the combined climate change conditions. This could describe its higher mortality rates compared to P. compressa, which, in contrast, was able to obtain more than sufficient energy in future ocean conditions.
There were some physiological variations between surviving P. lobata corals under control and future ocean conditions.
The authors indicate, despite changing ocean conditions, the resilience of Porites species of corals to temperature and acidification, and their role in reef-building, offer hope that few reef ecosystems may be retained.
McLachlan, R. H., et al. (2022) Physiological acclimatization in Hawaiian corals following a 22-month shift in baseline seawater temperature and pH. Scientific Reports. doi.org/10.1038/s41598-022-06896-z