Written by: Sunny Liu
Edited by: Ulya Aligulova
Before you know it, it’s March. 2019 began with a bang; Parliament is increasingly chaotic with #Brexit. The Americans extended their poor track record in Vietnam. The weather celebrated the New Year in January with a polar vortex for the Americans, and surprised us all with a record-breakingly warm last week of February. While it’s great to bask in the sun, prolonged high temperatures has been linked with poorer quality of wine. This makes me anxious. So, this month’s climate column will be focused on ‘happy thoughts’: the discovery of heat-resistant corals and the potential for coral reef recovery!
Despite their appearances, corals aren’t plants. They are marine invertebrates in the animal kingdom, with a symbiotic relationship with photosynthetic algae that provides the corals with the energy required for survival. Importantly, they are the building blocks of coral reef ecosystems, which covers less than 0.1% of the ocean, yet account for nearly 25% of marine biodiversity. To put it simply, they are very important to the health of our oceans. However, corals are fragile; they are extremely sensitive the water conditions. Variations in temperature, pH, and oxygen levels can cause the coral to have a stress response of expelling the algae from its tissues. This is known as coral bleaching. Over a prolonged period of time, coral bleaching will result in the death of the corals, the coral reef, and the coral reef ecosystem.
Hence, due to man-made greenhouse effect, increased levels of CO2 result in severe coral bleaching via two mechanisms. Firstly, increased CO2 in the atmosphere result in increased levels of dissolved CO2 in the ocean water, which forms carbonic acid, lowering the pH. This induces pH stress while simultaneously dissolving their protective exoskeleton, which is composed of calcium carbonate, further stressing the corals. Secondly, increased CO2 result in increased warming effects. The ocean, being the natural heat sink of the Earth, absorbs much of the heat; increased water temperature creates heat stress in the coral. As a species, corals are very sensitive to the effects of global warming.
However, not all is lost! Palumbi et al. (2014) demonstrated heat acclimatization of corals, suggesting that coral survival may be more hopeful than modelled. In the US National Park of American Samoa on Ofu Island, heat-resistant populations of reef corals were discovered. There are two categories of pools on Ofu Island. In Highly Variable (HV) pools, temperatures can reach 35oC, far above the critical temperature of 30oC. In contrast, temperatures rarely exceed 32oC in Moderately Variable (MV) pools. Due to natural selection in the local environment, corals in HV pools are more heat-resistant than those of MV pools, retaining more of the symbiotic algae in their tissues after heat exposure. To test for possibility of heat-acclimatization within a short period, Palumbi transplanted corals from MV pools into HV pools. Using heat-acclimatized corals as benchmark, he found that corals are able to gradually acclimatize over time to the heated conditions. Gene expression experiments conducted in the same study also demonstrated an increase in expression of known heat-resistant proteins in corals transplanted from MV to HV pools, suggesting that the same mechanism of heat resistance may be involved.
Although Palumbi’s study is optimistic, transplanted MV corals do not necessarily achieve similar levels of heat resistance compared to HV natives. There needs to be better ways to repopulate the reefs with heat-resistant corals. Two professors from Australia developed a novel idea to do so. They collected and matured spawn from corals that survived the recent bleaching events into larvae. Using a robot (rather uncreatively named LarvalBot) designed to play ‘stork’, 100,000 heat-resistant larvae were released into bleached regions of the Great Barrier Reef.
Realistically, the results of LarvalBot are unclear. However, it is symbolic of human ingenuity to overcome adversity to ensure the continuation of not just our species, but of our earth as well. It speaks of the human condition – to press on hopefully in our continued struggles, against the environment and, sometimes, others. January wasn’t great for the environment – we’ve got increasing extreme weather patterns, politicians who can’t be arsed (or worst, believe in ‘alternative facts’ about climate change), and a dam that collapsed in Brazil, releasing toxic sludge. It may feel like we’re approaching the end game, but we’re not quite there yet.
Switch off your lights. Consume less dairy. Eat less beef. Start by switching your own habits. And maybe, just maybe, we’ll be able to keep Earth inhabitable for future generations to come. Just maybe, but ‘maybe’ is all we need. It might be all we have.
Barshis, D. J., Ladner, J. T., Oliver, T. A., Seneca, F. O., Traylor-Knowles, N., & Palumbi, S. R. (2013). Genomic basis for coral resilience to climate change. Proceedings of the National Academy of Sciences, 110(4), 1387-1392.
van Oppen, M. J., Oliver, J. K., Putnam, H. M., & Gates, R. D. (2015). Building coral reef resilience through assisted evolution. Proceedings of the National Academy of Sciences, 112(8), 2307-2313.