Engineering hope for coral reefs in warming oceans

How naturally heat resistant corals could help preserve our reefs 

Maritimers have a long history of knowing just how interconnected ocean life is and how important it is to keep critical marine ecosystems functioning. From lobsters and cod, to shellfish and kelp, the health of one species will often impact the health of another. As we look to the future impacts of climate change on marine ecosystems, one particular type of organism is finding itself in some pretty hot water, literally and figuratively–corals.


Coral reefs are home to some of our favourite celebrities, like Nemo and Dory, but while they are integral habitats, coral reefs are also living animals that are having to adapt in the face of climate change.


Coral is an animal composed of thousands of miniscule creatures called polyps that make calcium-carbonate exoskeleton shells, like snails, that grow together to form the largest biological structures on earth. Corals grow by layers of polyps growing on the shell beneath it, allowing a single colony to live for thousands of years. It is impressive teamwork for something only the size of a nickel to create a colony the size of a car.


Millions of people travel around the world to see the natural beauty and wonder of coral reefs, but we are unsure how much time we have left with this ecosystem. Many marine biology experts are seriously concerned how warming oceans affect coral polyp’s ability to grow. 


Polyps have a unique symbiotic relationship with microscopic algae called zooxanthellae. These plant-like organisms live in the hard exoskeleton made by polyps that act like a hotel to house thousands of itty-bitty algae. It is symbiotic because both organisms benefit from one another. Algae that live in polyp shells and feed on their waste, produce sugar in exchange for their room and board. The polyp then readily consumes the sugar from the comfort of its home—which becomes decorated by the brightly coloured algae.


The problem in this relationship arises when the temperature changes. If waters warm, like with climate change, polyps become irritable and kick the algae out. This process is termed coral bleaching–due to the white appearance of the exoskeleton when the algae is absent–and this can be fatal to corals. They not only lose their vibrant colors, but they lose their source of food, which is often fatal. Since these bleaching events are becoming more frequent, scientists are now looking for ways to help corals thrive as oceans change.


A recent study produced by scientists from the Hopkins Marine Station at Stanford University might have found a solution to help our cranky corals withstand warming waters. In their experiment, they used four species of corals and took baby pieces, like little buds, from mother corals growing in warm and cool waters. These babies were then planted in a coral nursery in the National Park of American Samoa in the Pacific Ocean. The baby corals grew together for two years and experienced two natural bleaching events, one in 2015 and the other in 2017. Researchers found that the babies from heat resistant mothers, originally from warm waters, rebounded quicker and grew three times faster after a bleaching event than those from cold water mothers. 


As a marine keen biology student, I can tell you that this finding is HUGE! It suggests that there is genetic relevance to heat resistance in corals because the babies from different mother groups reacted differently to the heat, even when growing side by side.


Mt. A SCUBA society member and environmental studies student Sarah Waldron is hopeful but apprehensive how long term these solutions are. She says, “I look at this as both a win and a cautionary tale. Yes, the coral is showing temperature resilience, but the only way to truly maintain sustainable restoration of coral reefs is to prevent any and all further damage to them. We cannot risk losing ecosystems such as coral reefs.”


Farming genetically resistant corals could be enormously positive for reef restoration efforts and help to promote healthy coral growth in damaged areas that were historically unable to withstand bleaching. However, this is only part of the puzzle. We must continue to be diligent in our efforts to slow global warming by reducing carbon emissions and moving to green energy. This new farming approach will hopefully buy us enough time to give corals back the environment they deserve, allowing them to continue building underwater fish cities for millennia to come.


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