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Growing Concerns for Coral Reefs

Devin O’Dea

Bleached Coral Reef

This dead coral reef has little hope of sustaining life. Photo courtesy of Freedigitalphotos.net

One often hears that ecology and the environment hold intrinsic value for the human race. Economists have now quantified that figure and can say with relative certainty that we are flushing billions down the drain. Coral reefs are some of the most abundant ecosystems on the planet whose services are worth an estimated $375 billion per year to the global economy. Reefs provide a habitat for approximately 4000 different species of fish, and they are the backbone of our modern fishing industry. Currently 75% of the world’s coral reefs are threatened by a variety of stress factors, and in some regions up to 95% of reefs have died off completely. Reef regeneration is a creative and exciting process attempting to restore and revitalize the valuable ecosystems across the globe.

bleached coral

The exposed skeleton of a bleached coral. Photo courtesy of Freedigitalphotos.net

The factors precipitating the decline of our world’s coral reefs are diverse and catastrophic. Coral reefs have the incredible ability to survive and self-regenerate following catastrophic natural events such as hurricanes and huge ocean swells, however the multitude and frequency of factors facilitating their recent decline have led scientists to deem their recovery unlikely if no action is taken. Although climate change, bringing warmer and more acidic waters, is predicted to be one of coral’s greatest threats in the future, anthropogenic acts are primarily responsible for decimating global reefs in our lifetimes. The high-level synopsis of these acts posits coastal development, watershed based pollution, marine-based pollution and damage, dredging, and overfishing or destructive fishing as the major threats to coral reef systems.

Invasive Lionfish

The lionfish, a new delicacy for spear fishers and conservationists alike. Photo courtesy of Freedigitalphotos.net

As a result of anthropogenic effects on reefs, massive die-outs have occurred, which has disrupted homeostasis and allowed invasive species to thrive. Algae and lionfish are two invasive organisms that pose a large threat to current reefs. Coral bleaching allows algae to cover the nutrient rich skeletons of hard corals, and over fishing coupled with the massive loss of urchins has reduced the species that once kept the algae in check. This has contributed to the rapid growth of algae on living corals, which prevents coral photosynthesis and leads to greater species loss. Lionfish have also invaded and flourished in many reef ecosystems consuming small fish species before they have a chance to reproduce, further exacerbating the over fishing problem.

It is at this global juncture, on the brink of losing 75% of our coral reefs  in the ensuing decades that marine biologists, activists, and ecologists have teamed up to take matters in their own hands. The movement to restore and regenerate coral reefs has sprouted simultaneously in distinct geospatial locations in recent years.  While there are a variety of different approaches to coral restoration, the guiding principles are the same. Groups are propagating corals in aquaculture labs, open ocean nurseries, shipwrecks, and man-made reef structures to increase the genetic diversity of coral and catalyze their recovery.

angel azul coral reef

Coral Fragments grow from a sunken sculpture depicted in the new documentary, Angel Azul. Photo courtesy of Jason deCaires Taylor.

As many corals reproduce asexually, hundreds of thousands of coral fragments are harvested and strapped, glued, wedged, wired, and tied to a number of reef structures in order to restore bleached or destroyed reef ecosystems. One coral, Acropora cervicornis, also known as the staghorn coral, can grow up to 15 cm linearly per branch per year. This has given researchers and activists hope and momentum as significant progress can be seen after only a few years.

Restoration efforts differ between structural, biological, and physical restoration depending on the needs of the local ecosystem and varying success factors. Structural restoration is necessary in areas where the reef has been degraded due to blast fishing, boat grounding, dredging, landslides or other areas where corals will not have a solid structure to attach to. This has been the advent of various man-made reef structures including shipwrecks, wire frames, and even life-size sculptures are sunk to create artificial reefs. Rigs to reefs is another example where retired oil rigs are re-purposed and converted into thriving reef ecosystems.

Gametes Released from Coral

Gametes are released from corals only once a year. Photo courtesy of New Heaven dive school

Biological restoration is necessary in areas with low connectivity to other reefs, coral populations with low reproductive capabilities, or where gametes (coral larvae) are unable to settle due to grazing, algae, and other factors. As gametes are only released once a year, due to coral’s synchronous spawning habits, divers attempt to collect them as they float to the surface in the middle of the night. These fertilized corals are then grown in controlled settings and released back into the ocean once they are large enough to attach to a reef structure.

Physical restoration is the most recent and experimental approach as it attempts to address the conditions surrounding the fecundity, or reproductive capacity of reefs. One approach is to create mid-water nurseries where corals have clear water (critical for photosynthesis), and a lack of predators, pollution, and eutrophication. These open ocean restoration efforts generally have higher survival rates and grow faster than similar colonies on natural reef. In addition, scientists have even experimented with using “biorock,” and other mineral accretion devices to create favorable conditions for coral development. These devices change the water chemistry around the (coral) structure using low voltage electrical energy. As a result of the electrolysis, pH levels are increased and carbonate salts are precipitated out of the water. This allows corals to devote less energy to skeletal formation and more resources to reproduction, tissue growth/repair, and immune system strength. Corals growing on mineral accretion devices grow 3-5 times faster than normal corals.

biorock structure

Divers carefully monitor a biorock structure at the Hin Fai restoration site in Thailand. Photo courtesy of New Heaven dive school

Although huge strides are being made in coral restoration, adaptation, and the use of designer corals to combat changing ocean conditions, the factors that threaten the existence of coral reefs still need to be addressed. The success of coral restoration efforts can be undermined by the continuation of detrimental practices that degrade our marine ecosystems. The fate of coral reefs and the world’s most-traded food commodity, fish, could be decided in our lifetime.

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