Overfishing, disease, degradation by human activities, and hurricane damage have brought about a dramatic shift in the ecology of coral reefs around Jamaica and in the Caribbean, according to Greenpeace. Most of the large predatory fish species, such as sharks and snappers, have almost disappeared as have sea turtles and manatees.
Now it appears that dust storms from Africa's deserts may also be killing the coral in the Caribbean Sea. US Geological Survey scientist Gene Shinn states, "I've been watching this for about 40 years. The years with high dust were the same years most of the coral were damaged." Shinn goes on to say, "No one has gotten into looking at the potential health effects of what dust does to the environment." Gene Shinn is a self-proclaimed "dust nut" who is trying to raise both funds and awareness of the problem.
Coral disease and attrition have been observed since the 1970s. During the same period scientists noticed that desertification in the northern areas of Africa was moving sand and other particulate matter across the Atlantic Ocean in the form of dust.
A dust storm swirls off the northewestern coast of Africa on February 26, 2000. Image courtesy of US Geological Survey
Earlier this year NASA's SeaWifs satellite captured one of the largest dust storms ever recorded by a spacecraft. The satellite image, on the right, illustrates the undeniable presence of suspended dust. This large concentration of dust is loaded with fungi, bacteria, and viruses that are deadly to coral. The dust is also rich in iron which acts like a fertilizer for reef-choking algae, and indeed has also been noted that algae infestation has been plaguing the Caribbean reefs. Gene Shinn believes that many of the problems related to the sickness of the coral are connected to the estimated two billion tons of dust that annually blow from Africa to the Caribbean. He says "After we looked around, we noticed coral was dying all over the Caribbean, not just in Florida where we have sewage and other problems."
Aspergillis, a common fungus normally found in soil has devastated one particular species of coral, and may be connected to some human respiratory problems as well. Since 1983, when Aspergillis first appeared, it has killed more than 90 percent of the Caribbean's sea fans. That same year, an unusually dusty year, the number of Diadema sea urchins drastically declined, which, in turn, triggered algal infestations in the reefs.
"It's a veritable soup of stuff," Shinn said. These dust clouds from Africa carry literally tons of spores similar to Aspergillis. Millions of dollars have been spent researching sedimentation, sewage, pollution, ship groundings, temperature, and other coral enemies. But none of these potential killers explain why coral disease and algal infestation occur at the same time throughout the Caribbean where there is little human activity.
This healthy star coral at Grecian Rocks as it was in 1988. Image courtesy of US Geological Survey.
Nevertheless, the images to the right evidence the disturbing contrast between the healthy coral of 1988 and the same coral today.
One early theory had blamed this demise of coral on deforestation runoff. Shinn blames dust balls. "We looked at the dust," said Shinn. "That would explain howit could be all around the Caribbean, even in areas with no forests around." In fact, scientists have determined that the African dust so harmful to coral may have an upside, since it supplies most of the essential nutrients for the rain forest.
The same coral as it appeared in 1998. Image courtesy of USGS.
"After we looked around and noticed coral was dying all over the Caribbean, not just in Florida where we have sewage and other problems, I found some literature on the Amazon rain forest," Shinn said. "In the late '80s and early '90s, scientists determined that the African dust supplies most of the essential nutrients for the rain forest."
It is essential that we understand the relationship between African dust and the demise of coral reefs so that we can redirect research efforts. Scientists are analyzing dust trapped in coral skeletons.
|"It is essential that we understand the relationship between African dust and the demise of coral reefs so that we can redirect research efforts."|
This data will be compared with climate records and dust levels from key Caribbean collection sites.
In the meantime, what can be done? Plans are to collect new coral cores from the Caribbean reefs in the Virgin Islands. Older coral cores, stored in a Florida laboratory, will be analyzed for any correlation with the new cores. Other microbiologists will examine fresh dust collected in the Virgin Islands for fungal and bacterial spores. "All I'm trying to do is make people aware, because most don't even think of this," said Shinn. "And it does affect people's health, no doubt about it."
For more information visit coral.aoml.noaa.gov/agra/update.html
Status of Caribbean Reefs
Since June 1998, 13 large-scale AGRRA assessments have been completed and the results are being prepared for publication. Support for the initiative has come from the The Henry Foundation, Barcardi Family Foundation, Hachette Filipacchi Foundation, National Geographic Society Committee for Research and Exploration, Ocean Research Education Foundation, United Nations Environmental Program, United States Department of Interior, and the World Bank/Netherlands Environment Partnership Program. Below are some of the highlights from these surveys.
Many reefs of the Wider Caribbean are in relatively good condition:
| ||Intermediate-deep reefs of the Flower Gardens, Los Roques, Venezuela, and Bonaire are in very good condition with all areas having high (40-50 percent) coral cover, large coral sizes, low macroalgae ( approximately less than 20 percent), low recent mortality ( approximately less than 2 percent), and good representations of fish populations. |
| ||The majority of other areas surveyed (Cayman Islands, St. Vincent, Andros, Turks and Caiços, and Cuba) are in good condition but with some moderate disturbances (e.g., overfishing, tourism). |
| ||The Andros Island Reef System, some 150 kilometers (93.2 miles) long, contains remarkably healthy shallow reefs with extensive stands of living Acropora palmata. |
| ||Old mortality of reef building corals is low to moderate (~20-30%) in most areas. |
| ||Although much of the Caribbean experienced a major coral bleaching event in the summer and fall of 1998, the majority of areas surveyed recovered with only minor coral mortality affecting selected species.|
| ||Herbivorous fish (e.g., scarids and acanthurids) abundances appear moderate to high in most areas.|
Selected reef areas are showing signs of disturbance and decline:
| ||Moderate to severe coral mortality was observed in portions of the Bahamas and in much of South Central Belize and Honduras associated with the 1998 bleaching event. |
| ||Significant amounts of standing old dead Acropora occur in portions of Mexico, Bahamas, Turks and Caicos, Honduras, South Central Belize, and Venezuela. |
| ||Coral diseases are moderate to high in Belize, Honduras, and areas of the Bahamas and Cuba.|
| ||Macroalgal abundances are moderate to high ( more than 25 percent) in Belize, Honduras, Bahamas, Mexico, and Cuba. |
| ||Herbivorous fish abundances are low in San Salvador, Bahamas, Cuba, and Mexico. Low abundances and smaller sizes of commercial fishes are found in these same areas, as well as in St. Vincent. |
There are currently additional assessments underway in Mexico, US Virgin Islands, Saba, Belize, Curaçao, and Brazil. Goals for the AGGRA Program over the next two years include collaboration of team leaders to synthesize data for regional comparisons of reef condition, developing a regional database accessible to all, and expanding assessments to additional areas in the region. The target date for completing the assessment of the Western Atlantic and Gulf of Mexico region is the end of the year 2001. AGRRA welcomes collaboration and partnerships with individuals and organizations interested in this large-scale effort.