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By Annan Boodram |
May 2004: They are those gorgeous, eye-popping, fish-nourishing, ship-scraping biological wonders that are among the Caribbean's crown jewels. However, over the past few years there have been conflicting reports as to the extent to which the world's coral reefs have been damaged and just how replenishable are these "rainforests of the deep".
In fact more than half of the world's coral reefs will be damaged beyond repair by the year 2100 unless action is taken to halt the many threats they now face. according to a Pew Center on Global Climate Change report issuedin January in Washington.
Coral Reefs
Built by a variety of coral and other species that secrete skeletons of calcium carbonate that accumulate over time, coral reefs can grow to be massive structures extending over wide areas of shallow tropical and subtropical seas. Reef building corals contain tiny cells of symbiotic algae that convert sunlight and nutrients into fuel for coral growth and production. Because they depend on light, coral reefs require clear water for growth and can be severely damaged by sediment or other factors that reduce water clarity or quality.
Caribbean Reefs
In July 2003, UK scientists reported "a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades."
The authors analysed the results of 65 separate studies of 263 sites. Their results showed patterns of change in coral cover varied across time periods, but were largely consistent across sub-regions.
In the December 2003 issue of the journal Ecology Letters, assistant professor of marine sciences at the University of North Carolina at Chapel Hill, Dr. John Bruno, is quoted as saying, "Caribbean coral reefs have declined dramatically over the past 20 years or so as disease epidemics have swept through themIn less than a year, the two most common species that covered 60 to 70 percent of the bottom were just wiped out, becoming functionally extinct and changing possibly forever the structure of those marine communities."
Threats to Caribbean Corals
These damaged reefs suffered from a combination of problems, including disease, habitat loss, natural factors like hurricanes, invasive species, overexploitation, pollution, global warming and weakening from the warmer waters of El Nino.
With respect to global warming, scientists say human emissions of carbon dioxide (CO2) and other greenhouse gases, (blamed for global warming), are endangering reefs in two ways.
The first is to increase the incidence of "bleaching" events, in which warmer waters weaken or kill corals and other reef-building species by causing them to eject the vital algae that live within their tissues.
The second damaging effect of CO2 rises is to change the chemistry of the ocean. As the gas builds up in the atmosphere, more of it is dissolved into the ocean, lowering concentrations of the carbonate ion, a building block of the calcium carbonate that corals and other organisms use to grow their skeletons and build up reefs.
"We are making the oceans more acidic and we know that corals and many other organisms that secrete the calcium carbonate - limestone - that forms their skeletons grow more slowly under these conditions," said Dr Joan Kleypas, from the US National Center for Atmospheric Research and a co-author on the Pew report.
Additonally, according to Austrian born, Dr. Sascha Steiner, Marine Biologist and Founder/CoExecutive Officer of the Institute for Tropical Marine Ecology (ITME), recent trends in land use, in agriculture, road construction and quarry operations are responsible for endangering the coral reefs in Dominica (and other parts of the Caribbean). According to Steiner, the nets and fish pots of local fishermen sometimes entangle with the corals and harm them. Sedimentation and fresh water from rivers are also contributing factors.
Also last year Dr. Bruno and colleagues at other U.S. universities, conducted field experiments off Mexico's Yucatan Peninsula and concluded that chemical nutrients washed and dumped into the sea can increase the severity of coral diseases. They looked specifically at the fungi Aspergillus, which kills elegant gorgonian sea fans through a disease known as aspergillosis and two species of the reef-building corals Montastraea, which yellow band disease can kill.
The researchers placed various concentrations of time-release fertilizer rich in nitrogen and phosphorus in porous bags made from pantyhose and suspended them at sites on reefs some four to six inches from living colonies of the tiny animals. That enabled them to manipulate and boost nutrient levels in the water.
"We found that even modest rises in nutrient pollution could increase mortality of the three important Caribbean corals by facilitating the spread of disease," Bruno said. "Our results suggest that further steps should be taken to reduce nutrient pollution from agricultural runoff, sewage pollution and deforestation."
By increasing nutrient concentrations between two- and five-fold, the marine biologists recorded almost a doubling of tissue loss among the Monastraea from yellow band disease, he said. A separate experiment showed nutrient enrichment significantly increased two measures of the severity of sea fan aspergillosis.
"What we did was relatively minor enrichment so we were not doing it to the extent you might find in the Chesapeake Bay or the coastal Carolinas near a pig farm or something," Bruno said. "We did what we thought would be comparable to what is happening in the Caribbean."
Value of Coral Reefs
Destruction of the world's coral reefs have major implications for human communities that live close to reefs, said Dr Aronson, from the Dauphin Island Sea Lab in Alabama.
"Tens of millions of people depend on reefs to provide them with food and to protect tropical shorelines from erosion," he told the Seattle meeting.
"In economic terms, a conservative estimate puts the total annual income from the world's coral reefs at $30bn - a huge amount of money.
"Coral reefs also have great aesthetic value and support a huge biodiversity with some estimates running into the millions of species."
Additionally coral, could be used in the pharmaceutical industry, as is done in the United States of America and Japan, according to Dr. Sascha Steiner. He added that in addition to being a tourist attraction, coral reefs are a condominium and habitat for a variety of fish species that feed on the plankton to be found among the corals. He noted that atolls or little islands formed by the building of coral masses that rise above the surface, could prevent the destruction of wave action caused by hurricanes.
Furthermore, a special type of coral with an internal skeleton is used in the making of expensive jewellery. The hard skeleton is cut and polished into exquisite designs.
All of this was best summed up by the president of the US Marine Conservation Biology Institute Dr. Elliot Norse who told the BBC last July, "They (corals) are sources of future medicines, they are recorders of global climate change because they live so long, and they provide habitat for many other species (especially the big and valuable commercial species - cod, orange roughy, armorhead, grenadier and Chilean bass). They are also exquisitely beautiful organisms."
Corrective Action Needed
Said Eileen Claussen, president of the Pew Center. "If we fail to act, the destruction of these rare and important ecosystems will continue unabated, threatening one of our world's most precious natural resources."
Dr Terry Done, from the Australian Institute of Marine Science, commented: "We need to slow the rate of global warming, clean up the watersheds that drain into coral reef waters, stop overfishing and start an ecosystem-based management approach to coral reefs and their fisheries.
And, last year, in advocating a more proactive approach to the efforts to raise the level of awareness on environmental issues, particularly as it relates to the marine environment, Dr. Steiner issued a call for the sea to be recognised as a natural resource.
Positive Caribbean News
In this context there have been some positive news for the Caribbean. To begin with one interesting side-effect of the warming waters could be seen in the way elkhorn and staghorn corals, two important and temperature-sensitive species on Caribbean reefs, were now expanding their populations northward along the east coast of the Florida Peninsula. These species last lived at this location 6,000 years ago when the climate was warmer.
Secondly an inspection of deeper-water Caribbean coral reefs found them healthier than previously believed, scientists said.
A three-year survey of 20 coral reef areas in the western Atlantic found those in 20 feet (6 meters) to 65 feet (19.5 meters) of water had an average of 26 percent living coral cover.
Previous studies in both shallow and deep water have found as little as 15 percent coral cover, said Robert Ginsburg, a professor of marine geology and geophysics at the University of Miami.
Also the presence in the Caribbean of Institute for Tropical Marine Ecology (ITME), is certainly a positive measure. The ITME is headquartered in Belfast and was established in 1999. ITME has conducted research programmes on coral reef health and structure, and a variety of biological projects. The scientific data, which Steiner regards as pioneering work, is made available to governmental and non-governmental institutions in Dominica and disseminated worldwide via international scientific journals.
Another positive note was the news that US Department of the Interior's U.S. Fish and Wildlife Service is contributing $200,000 to assist states and territories with local projects to protect coral reefs and the species that depend on them. This announcement was made by Assistant US Secretary of Interior for Fish and Wildlife and Parks Craig Manson announced at the 10th meeting of the U.S. Coral Reef Task Force in October 2003.
The task force is focusing on lessening human impacts on these ecosystems, restoring reefs, and educating the public on the threats to reefs. It will also address international trade in coral reef species.
Yet another piece of good news came from Dr. Bruno and his colleagues who feel that, "we might be able to do something about lowering the growing nutrient levels through regulations or other methods," thereby helping to decrease the severity of coral diseases.
Finally, also last year, more than 1,100 marine scientists signed a statement calling on the UN and world governments to stop the destruction of deep-sea corals.