Coral reefs

You've heard about them but do you really know what they are or what they do?

First of all corals aren't plants, they're tiny animals who just happen to look like plants and flowers...pretty cool huh?

In terms of biodiversity, coral reefs are the rainforests of the ocean, providing shelter for some of the highest concentrations and diversity of life on the planet. Unfortunately, coral reefs are also facing severe challenges to their continued existence, just as rainforests are.

Coral reefs develop when coral polyps, (the tiny animals), fix carbon dioxide from the atmosphere and calcium from seawater to form layers of calcium carbonate, one on top of the other. Key to this process are tiny symbiotic algae called Zooxanthellae, which take in sunlight and carbon dioxide and give back oxygen and other nutrients that the Polyp needs to survive. Elegant as this symbiotic relationship is, it also means that Coral are sensitive to changes in their environment. Corals are found in shallow water because the Zooxanthellae need sunlight to carry out photosynthesis. If the water is clouded with pollutants or algal blooms, they die, which means the coral dies.

Coral reefs not only offer protection and habitat for fish and sea creatures, they also protect shore communities from storm surges and rising tides. Worldwide, it's estimated that 500 million people are dependent on the ocean's coral reefs for food, tourism income, and coastal protection.

Over time, coral reefs can form huge structures, such as Australia's Great Barrier Reef in the Pacific - a living object so large it can be seen from space. The distinctive atoll shapes of paradise destinations, like Bora Bora and Tahiti, are due to fringing coral reefs. As the volcanic island slowly sinks with the moving continental crust, layers of coral build around the perimeter. Over time, all that is left is a ring of coral. Islands such as these in the Maldives are examples of fringing coral reefs.

Photo public domain

So what are the threats?

A warmer earth simply means warmer oceans. A change in water temperature as small as one degree can lead to coral bleaching - the loss of the thin living layer of coral polyps covering the reef. Once this happens, the breathtaking colors of the reef disappear, leaving the rock-like skeleton exposed and lifeless.

Coral bleaching means much more than just the loss of our reefs however. These ecosystems provide the foundation for many of the ocean's food chains. In a time when world fisheries are quickly being depleted, further habitat loss could lead to mass extinction of marine life.

Besides Global warming, agricultural runoff and untreated waste flowing into our oceans also threatens coral reefs. Increased nitrogen levels from fertilizer runoff can cause "red tides," massive blooms of phytoplankton populations, which can choke off coral's natural defenses.

The things we dump into the oceans don't just stay there. Again, what goes around comes around. The agricultural runoff and untreated sewage we dump into the ocean eventually finds it's way back to us in the fish we eat. Preserving life is an instinct we all share. And ultimately, protecting our coral reefs is not just a way of ensuring healthy marine environments, it's also a way of ensuring our children and ourselves the healthiest possible food and water.

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