When most people think of a coral reef they are imagining a sunny tropical beach, but many coral species are actually found in the dark, cold waters of the deep sea. These corals, commonly known as cold-water corals due to their preference for low temperatures, form beautiful ecosystems that are teeming with life. One of the largest threats to these slow-growing and fragile ecosystems is ocean acidification, the gradual reduction in the pH of our oceans caused by the excess carbon dioxide humans emit into the atmosphere. By the year 2100, it is expected that over 70% of stony corals in the deep sea will live in waters that are so acidic that they may corrode corals and make it difficult or even impossible for them to form hard skeletons.
In a previous publication scientists from Marine Conservation Institute and Temple University showed that cold-water corals in different ocean basins had completely opposite responses to ocean acidification, suggesting some populations may be much more resilient to climate change. What about individual corals within a population – could they also exhibit different responses? Enter the hunt for a ‘super coral’, corals with a genetic makeup that render them more resilient to ocean acidification. In an increasingly acidic ocean super corals would have higher survival and reproductive rates, and over many generations would comprise an increasingly large portion of the population. If these super corals already exist in the deep sea, there is a chance that cold-water coral populations may be able to adapt quickly enough to survive in the face of climate change.
In a recent publication coauthored by Marine Conservation Institute staff scientist Dr. Samuel Georgian, the effect of ocean acidification on the cold-water coral Lophelia pertusa was assessed using both short and long-term experiments. The study examined how well individual genotypes – corals with distinct genetic makeups – were able to calcify new skeleton material in the low pH conditions predicted to occur with ocean acidification. In the short-term experiment, some genotypes were still able to calcify new skeleton in very low pH conditions, while other genotype’s skeletons began to dissolve. Interestingly, the same genotypes that could calcify under low pH conditions (i.e., more acidic water) in the short-term experiment also proved to be much more resilient to ocean acidification in the long-term experiment. These results suggest that even within one population, cold-water corals may have very different responses to ocean acidification and other stresses. However, more research is needed to determine if this genotype is truly a ‘super coral’, and whether these populations have the capability to adapt to future levels of ocean acidification.
While the hunt for super corals continues, it is absolutely imperative to better protect these fragile ecosystems before they are irrevocably damaged by other threats such as bottom trawling and oil and natural gas extraction. (…)
Sam Georgian, On the tide, 19 May 2017. Article.
