Caring for Coral: Scientists and Ecologists Reconsider the Best Methods to Preserve Coral Communities

By Sara Klimek

March 3, 2018

Corals are some of the most fascinating and complex organisms on planet Earth. Like true comrades, singular coral polyps coexist and build around each other. They are some of the world’s most efficient minimalists; they utilize each other's thin, limestone exoskeletons to anchor their nickel-sized bodies onto rock and then reproduce to form more colonies.

These colonies, consisting of millions of coral polyps, create intricate structures known as coral reefs, which are essential to aquatic communities. Reefs provide habitat for close to 25% of the world’s fish biodiversity. Like a good neighbor, they provide food and habitat for several tropical reef fish. Parrotfish have one of the most interesting relationships with soft coral. As demersal spawners, Parrotfish lay their eggs on the base of the corals to protect them from incoming waves and potential predators. In return, parrotfish eat algae off of the corals, thus improving the corals’ photosynthetic capability.

Corals also have a symbiotic relationship with zooxanthellae algae, which give corals their very distinctive bright colors, thus adding aesthetic value for aquarium afficinatos who want particular corals in their saltwater tank. Zooxanthellae are arguably one of the most important algal structures in the entire ocean ecosystem because they use metabolic waste from the polyp to photosynthesize, similar to very tiny recycling machines. Without zooxanthellae, corals could not survive.

Changes in ocean chemistry, such as coral bleaching, are threatening the relationship between zooxanthellae and corals.  Coral bleaching is the process by which environmental stressors cause corals to expel their zooxanthellae algae. Changes in temperature and pH are some of the most widely studied factors that contribute to coral bleaching. Branching corals are very susceptible to coral bleaching because of their nearly decade-long growth cycle and vulnerability to storm damage. After all, the rate of coral bleaching is not slowing down anytime soon; scientists at Yale University found that in 2016, nearly 55% of the world’s reefs were affected by bleaching. Scientists expect that number to increase in the coming years.

The most definitive explanation for dramatic changes in ocean chemistry is an increase in carbon dioxide emissions. As carbon dioxide is released into the atmosphere, it is absorbed by water and converted to carbonic acid. Carbonic acid is then absorbed by calcium carbonate structures within the ocean. This process, called the oceanic carbon buffering system, reduces free acid in the oceans, thus regulating pH. Corals rely on former calcium-rich coral growth to continue their cyclical growth cycle and to form reefs.

The global aquarium trade, including both corals and animals like clownfish and mollusks, has an estimated value of $330 million per year. Southeast Asian countries are especially vital in the global coral trade. Indonesia exports nearly 900,000 stony corals per year, a value set to increase as stony coral use for aquariums, lime manufacturing, and jewelry increases as well. Fleshy, soft corals like hammer coral (Euphyllia spp.) and flower pot coral (Goniopora) are more common in the trade because they must continually be replaced due to their poor ability to survive in captivity. Aquarium collectors are willing to pay to have the most beautiful corals in their aquariums, increasing the demand and stress on reefs. Removing corals can inhibit future generations from growing on the reef, thus slowing habitat creation for other marine organisms.

Researchers are turning to indoor coral farms to help satisfy the aquarium trade and remediate damaged reefs. This form of ornamental aquaculture relies on technology for the biomimicry of natural coral ecosystems. Actinic lights to simulate photosynthesis, magnesium and calcium additives to ensure optimal growth, and pumps to simulate wave action are fairly common in coral propagation systems to ensure efficient growth and similar conditions that corals experience in the wild.

The process of “coral farming” involves taking large pieces of coral and “fragging,” or separating, it into several smaller pieces. The coral is fragged at regular intervals  to promote the growth of fresh polyps. Aquaculturists not only grow popular aquarium species, but have started growing already resilient species to replace bleached reefs. Biologists can use a lab to raise healthy corals and then slowly familiarize them with actual ocean conditions by building gigantic offshore coral racks. After a few months, these corals will be transferred to reef rock and will provide habitat for the ocean’s immense biodiversity.

Coral biologist Ruth Gates once claimed that her conservation coral propagation research acknowledges that the future of nature may not entirely be natural. For centuries, humans have, through genetics and artificial selection, been able to produce the greatest possible meat grade in cattle, fed more societies than ever before, and remediated areas of degraded tundra ecosystems. Technology has given humans the ability to exploit the natural world, but only time will tell if technology has the ability to help us mitigate our impact. By creating a better and more efficient method of coral propagation, we may be able to avoid future overexploitation of our reefs