They've outlived the dinosaurs and a whole lot more, but global warming may yet kill off the coelacanth. Scientists fear the coelacanth - a "living fossil" fish that has been swimming the seas for an astonishing 400 million years - will be threatened if changes in ocean temperatures lead to the destruction of life-nurturing coral reef systems. "The coelacanths are vulnerable and global warming could affect them adversely," explained Horst Kleinschmidt, deputy director general of South Africa's department of environmental affairs and tourism. "They are only found at certain depths, so they are no doubt susceptible to changes in the water temperature," he said. Rising sea temperatures associated with global warming - which scientists have linked to the use of carbon-based fossil fuels - have been cited as one of the leading causes behind the destruction of about a quarter of the world's coral reefs. Other factors contributing to the decline of the "ocean's forests" include pollution, over-fishing and dynamiting. A 1000 page UN report earlier this year warned that coral reefs in most regions could be wiped out in 30 to 50 years if sea temperatures reach such a point that the bleaching of the reefs becomes an annual event. Coral is a soft living organism - a combination of single-plant cells and animal tissues - which secretes a hard skeleton of calcium carbonate. One theory holds that the increase in sea temperature obstructs the production of natural sun screen chemicals which then makes the corals more sensitive to light. This leads the animal tissues to expel the single-plant cells which give pigment to the coral. The coral then turns white or bleaches and also starves because the plant cells provide it with its main source of food. Among the reefs under threat are the stunning coral systems off Sodwana Bay on South Africa's Indian Ocean coast. Sodwana's reefs are a scuba diver's delight, teeming with schools of brightly colored tropical fish amid stunning coral formations that rise up from the ocean floor. Magnificent sting rays glide silently past while sinister-looking moray eels wait patiently in crevices for prey. Further out and at depths below 100 meters (330 feet) lies Sodwana's coelacanth colony, discovered by chance by a group of divers last October. Coelacanth once believed extinct The coelacanth was believed to have been extinct for 70 million years until one was caught by a trawler off South Africa in 1938 and identified by a museum curator. That catch stunned the scientific world and is widely regarded as the zoological discovery of the 20th century. Subsequently found near the Comoro Islands off Africa's east coast, and more recently off Indonesia, no live specimens were ever found or seen off South Africa until last year's sightings. But if the reefs of Sodwana suffer from global warming, the coelacanth may be one of many species to pay the price. "Most of the food that does come into the coelacanth's environment is derived from the shallow water coral reef community which is above the coelacanth's habitat," said Dr Phillip Heemstra, a marine biologist at the J.L.B. Smith Institute of Ichthyology in Grahamstown, South Africa. | | Coelacanth "If the rise in sea water temperature kills the coral it could decimate the coelacanth population," he said. Changes in water temperature could also force the fish down to even greater depths. All of the sightings of the fish from submersible craft or by scuba divers have been below 100 meters (330 feet). "It would probably want to go deeper where the water is cooler because it's adapted for a specific temperature regime," said Heemstra. "But the deeper it goes the less food it's going to find." The coelacanth, which can attain lengths of two metres (six feet six inches) or more, is also a slow reproducer, adding to its vulnerability. Scientists believe it doesn't reach sexual maturity until it is between 13 and 20 years old. It gives live birth with litters known to number as high as 26 - very few compared to the hundreds or even thousands of eggs spawned by many other fish species. World has changed, coelacanth has not Life on the planet has undergone dramatic change since the coelacanth first appeared on the scene. The only life forms found on the Earth's barren wastes of dry land 400 million years ago were invertebrates such as spiders, mites, scorpions and centipedes. Fish were the only animals with backbones. Four-legged, amphibian-like animals eventually ventured from the water onto dry land. Creatures that laid eggs on dry land appeared later and evolved into the ancestors of all subsequent birds, mammals and reptiles. The reptiles reached their zenith in the age of the dinosaurs, which ended abruptly 65 million years ago, possibly as a result of a global catastrophe unleashed by a collision between the Earth and a massive meteorite. But the coelacanth, quietly nestled in its underwater caves and canyons, lived through it all and changed little. It still retains its fan-like tail and additional, limb-like fins, which have earned it the nick-name "Old Four Legs". It remains to be seen if this astonishingly resilient survivor from the distant past can adapt to the challenge of rising sea temperatures. If it can't, it will follow the dinosaurs and countless other species down the path of extinction. |
