Corals of the World Quickly Vanishing
Coral reefs, home to 25% of marine biodiversity, are collapsing.
Aug 29, 2008
What Coral Reefs Are
Coral reefs are the largest living structure on Earth. The Great Barrier Reef off the coast of Eastern Australia, for instance, is the only living organism clearly visible from space. Reefs are made up of millions of simple individual organisms called polyps (or Cnidarians) which create limestone skeletons around them by collecting calcium from seawater. The individual polyps reproduce asexually by what is called budding, or by making identical copies of themselves. The bright colors of corals come from the symbiotic algae that live within them, and together they support a wide variety of biodiversity. In fact, if managed sustainably, coral reefs can yield in average 15 tones of fish and other seafood for every square kilometer annually.
If the symbiotic algae die, and are released from the corals, the corals turn to a pale, gray color. This is called bleaching and many coral reefs do not recover from the event. These algae are needed to keep the corals alive, as well as for the nourishment of other marine creatures. Corals may become ill, lose their symbiotic algae and suffer from bleaching when exposed to pollution or chemicals, to sodium cyanide (used to stunt fish for easy capture), and higher temperatures. In recent years, scientists have been documenting an unprecedented occurrence of coral bleaching events throughout the world, and have found compelling evidence that points to the culprit, global warming.
Unsustainable Fishing and Other Threats to Coral Reefs
Coral reefs are ancient ecosystems which have withstood tens of thousands of years of changes in the oceans. However, more recent changes from man-made pressures may put reefs beyond survival and adaptation. Among the threats to coral reefs worldwide, one of the most serious, aside from climate change, is destructive or unsustainable fishing practices including the use of cyanide for easy capture of fish, bottom trawling (or deep sea- bottom fishing) and over fishing in general, which affects the reef biodiversity and its natural biological balance.
Cyanide fishing consists of spraying sodium cyanide on coral reefs to stunt some fish for easy capture for the aquarium trade, or for the consumption of live fish in restaurants (mostly in Hong Kong, Singapore, and mainland China). As an example, in Hong Kong, 20,000 tones of live reef fish is eaten annually in restaurants. The fish captured using cyanide die soon after as a result from severe liver damage, and corals and algae die when exposed to the cyanide. World Wildlife Fund scientists estimate that for every single live fish caught with sodium cyanide, “a square meter of their coral reef home is killed.”
Rampant and careless tourism has also continued to threaten and impair coral reefs, such as dropping anchors directly on coral reefs, or careless snorkeling and diving. Cruise ships and beach resorts that empty their sewage into coastal waters are also poisoning coral reefs. Additionally, coral reefs live precariously close to their thermal limits, meaning that any temperature increase entails the risk of disease, bleaching events and, eventually, death.
