Can Science Save our Reefs?

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Issue 10, Volume 112

By Sophia Wan-Brodsky 

Vibrant scenes of alien-like grooves and inflated polyps decorate the seafloor; this is often what comes to mind when we envision a coral reef. Few underwater animals are as iconic as corals, a significant keystone species. Despite covering less than one percent of the sea floor, reefs house a staggering 25 percent of marine life. Often called “the rainforests of our oceans” for their amazing biodiversity, their importance extends beyond the water. Over half a billion people depend on coral reef ecosystems for food and income. Corals provide a powerful buffer against storms and floods, saving shorelines from erosion. They are also important sources of medical breakthroughs and new medicines. However, reef-building corals are threatened with extinction.

Coral is a colonial organism, meaning it is formed by genetically identical polyps. Polyps are soft-bodied organisms that produce calicle, a limestone skeleton. These corals depend on zooxanthellae, a photosynthetic algae that lives in the coral’s tissue and provides it with vital nutrients. When exposed to stressors such as pollution or temperature increase, corals eject the zooxanthellae and turn a ghostly white color in a process known as bleaching. Without the algae, the coral is damaged and eventually dies. In the past decade, an estimated 14 percent of coral have died due to rising ocean temperatures. Scientists predict that should oceans continue to warm, 70 to 90 percent of remaining reefs will die.

If we can’t prevent ocean warming and pollution, the future for coral reefs is bleak. That’s where technology comes in. For instance, the COTSbot acts like a terminator-robot by identifying and killing crown-of-thorns starfish (COTS). It’s a non-invasive species, but in many areas, COTS populations have boomed, likely due to the overfishing of its predators and nutrition from runoff. The COTS feeds on coral polyps, and unchecked growth leads to reef destruction. The COTSbot can autonomously navigate, identify COTS, and inject them with a bile salt to kill them. As of now issues still remain concerning the practicality and cost of the COTSbot, but the technology is highly effective at identifying and targeting the starfish.

One of the most common reef restoration techniques is coral farming, also known as coral aquaculture. Coral can reproduce sexually or asexually through fragmentation—a process in which a colony of polyps breaks off from the original coral. Coral farming is an artificial manifestation of coral fragmentation. Fragments of coral are taken to a controlled environment such as a lab or underwater farm. Micro-fragmentation, a technique in which a saw splits the corals into pieces that are one to five polyps in size, stimulates tissues in the new fragments to accelerate the growth to over 25 times the normal rate. This technique was accidentally discovered by Dr. David Vaughan, when he transferred elkhorn coral to a new tank and accidentally damaged it, causing several polyps to fall off. Sure that they wouldn’t survive, he was shocked to find that they had regenerated to the size of the original sample within a few weeks.

Scientists have also employed 3D printing technology to save reefs. They used various materials, such as concrete, limestone, and terracotta, to create an artificial skeleton for polyps and coral fragments to grow on. Sometimes, the 3D-printed object is used simply to mimic the role of natural coral by providing reef inhabitants with a structure to interact with. A group of researchers from the University of San Diego and the University of Cambridge used polymer gels, hydrogels, and cellulose to copy coral tissue. They created a microhabitat for zooxanthellae, allowing for coral-algae symbiosis and increased cultivation of algae.

Scientists are still determining whether genetic engineering is another possible solution. CRISPR-Cas9 gene editing has proven successful in multiple proof-of-concept studies on coral and points toward scientists creating a “super coral” that can withstand the worsening environmental conditions. Continued progress in the sequencing of coral genomes will help scientists identify what genes yield resilience in those species. Some are looking to modify the symbiotic algae rather than the coral itself. Specifically, scientists want to increase their heat tolerance. In a process known as “directed evolution,” cultured algae was exposed to increasingly high temperatures over a prolonged period. This selects for the most heat-resistant algae, thus yielding a population capable of withstanding greater fluctuations in temperature. This work is relatively new, so only time will tell if this approach to genetic engineering can be effectively implemented.

Innovations like these create hope for our reefs. The challenges faced by coral reefs are largely man-made, but perhaps humans can compensate with solutions. Currently, coral farming provides the most consistent and immediate relief to failing reefs. It has been used far longer than the new methods of coral conservation such as COTSbot and 3D printing. With more development, these less common methods could be implemented on a larger scale to supplement aquaculture efforts. The future of our ocean might not be so bleak after all.