CORAL REEFS

In the tropical and subtropical regions of three major oceans—the Pacific, Atlantic and Indian—there is an abundance of coral reefs of varying sizes. They lie no deeper than about 200 feet below the ocean surface, for corals require sufficient sunlight, clear water, the presence of zooxanthellae or algae, which support them in photosynthesis, and a temperature range of 17 to 34 degrees Celsius in order to thrive.  Because of these specific ecological requirements, corals do not establish themselves randomly and are mostly found in areas where shallow submarine platforms occur in the earth’s southern hemisphere. The less optimal the conditions, the smaller and more fragmented the corals are, particularly toward the Atlantic Ocean basin and in areas in the eastern Pacific, off western Australia and southern Japan. These appear to be the limits where some corals are able to tolerate less ideal conditions.

When the requisites are met, corals can grow into massive structures. Living organisms, particularly the coral polyp, secrete calcium carbonate to create the hard exoskeleton of the coral. In time, coral colonies form a reef, an ecosystem of great diversity and interconnectedness. As a reef continues to grow and expand, it takes on one of the three major characteristic structures: fringing, which projects seaward from the shore; barrier, which borders the shoreline but is at a greater distance from it than fringing coral; and atoll, which forms around a volcanic island that descends below sea level as the coral grows upward. Not all reefs fall under these classifications, and there are some that appear to be a combination.

However the reef forms, within its ecosystem, associations occur among the organisms that inhabit the corals. Crustaceans, including shrimp, crabs and lobsters, seek protection from predators in the branches of the coral. Octopuses and squid live near corals, feeding on food particles as they float by. Even the shark and other solitary fish as well as schools of fish benefit from the presence of corals. It is not an overstatement to say that corals are a critical source of life for numerous marine organisms. In fact, many describe coral reefs as the “rainforests of the seas,” and like rainforests, if destroyed, the organisms that depend on them either become endangered or are eliminated entirely.

In the past few decades, scientists have discovered that corals are important to humans in myriad ways. They not only provide a crucial ecosystem for the ocean and support the biodiversity within it, but they also remove and recycle carbon dioxide from the air and shelter land from ocean storms and floods. Moreover, coral reefs attract tourists, providing jobs valued at about $375 billion annually. More recently, it was determined that corals can be used to create medicine for diseases such as cancer and osteoporosis. If corals are so valuable to humans and are paramount in maintaining the health of the oceans, why are coral reefs being destroyed by man?

Research studies indicate that the primary dangers to coral reefs are all man-made. For example, when ocean waters become too warm, corals expel the zooxanthellae living in their tissues. This causes the corals to turn white in color, a phenomenon known as coral bleaching. Although the coral is not dead, it is in a condition where death becomes more likely. Elevated sea surface temperatures are caused by global warming and the rising levels of carbon dioxide in the ocean, all attributable to how human beings are using earth’s resources. The use of pesticides and synthetic fertilizers, chemical pollution from factories, sedimentation due to dredging, poor land use and deforestation, and the presence of oil slicks, not to mention overfishing and overdevelopment of coastal areas, have all taken a toll on the corals of the sea. Secondary threats include the El Nino phenomenon, which increases ocean temperatures and predation by marine organisms. Cumulatively, these threats seem to be worsening from year to year, and this shows itself in the prevalence of disease in the corals.

A 2004 study concluded that about 70 percent of the world’s coral reefs were either being threatened or destroyed by human activity. Although some reefs have the potential for recovery, about 20 percent have no prospects for recovery. Jamaica’s reefs have been hardest hit, with about 95 percent dying or completely destroyed. A 2009 report on Australia’s Great Barrier Reef concluded that the decline of water quality due to catchment runoff, illegal fishing and poaching, and coastal development were ruining the resilience of the reef. Its health had deteriorated significantly since the Europeans first settled in Australia. The Australian government has made great effort to manage the reef, with the result that its ecosystem is more likely to survive than reefs located in other areas.

Whereas much attention has been given to the problem of global warming, coral reefs are low on the agenda for many governments, and this lack of political will to address the issue may result in a global die-off the reefs. The United States has prohibited its removal or destruction, and around the world, the Convention on International Trade in Endangered Species of Wild Fauna and Flora is responsible for regulating international trade of certain corals. But not enough is being done to save the corals. As it is, targets for reducing carbon dioxide emissions drawn up at the Kyoto Protocol in 1997 were not met, and a second summit had the United States asking that commitments made in the first summit be honored. In the end, these commitments were watered down. What then can be expected for the world’s corals?