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Importance
of Assessing Impacts of Nutrients
January 20 2006 Dear Mr. Adam, Thanks for keeping us posted on the latest captive dolphin developments in Grand Cayman. I can only speak on the ecological impacts of nutrients from captive dolphin pens on surrounding reef areas and the need to control them in Cayman to keep your waters as clean as possible. I have swum and filmed for miles on either side of three different captive dolphin facilities in Mexico, looking at the abundance and species distribution of algae on the bottom. Because I have learned their ecological patterns from watching algae spread for 50 years around nutrient sources in Jamaica and other islands all around the earth, I am one of only a handful of people in the world who can “read” the algae distributions to identify the sources of nutrients (this is why I was asked to write the review on the impacts of land-based nutrients on coral reefs and the prospects for controlling them for the United Nations Expert Meeting on Waste Management in Small Island Developing States a couple of years ago). There is no doubt that the problem of algae overgrowing and killing coral reefs is the nutrients, which act as fertilizers, regardless of their source. In almost all places dolphins are only fairly small contributors of nutrients compared to humans because of the vast difference in their populations (even though dolphins excrete as much as around 6 people). Nevertheless captive dolphins are major cause of excess algae growth in the Chankanaab Marine Park in Cozumel because the human sewage is diverted to the other end of the island. What we see are slimy mats of bacteria and algae smothering and killing corals, and the algae around the dolphin pens are the same ones that we see killing corals in expanding rings around the sewage outfalls in South Florida. The worst algae are not present on the upstream side of the dolphin pens, but all over the downstream side and killing corals for a kilometer or more beyond it. There is little groundwater flow to the sea, and since groundwater is Cozumel’s only source of water, they have done a remarkable job keeping it free of pollution. There is no algae buildup around where the groundwater springs flow into the sea, which we see in Jamaica because the groundwater is polluted at the source since people dump sewage and garbage into the sinkholes, acts that are strictly and effectively prohibited in Cozumel. At the Chankanaab Dolphin Park the nutrients from the dolphins were also increased by nutrients from sea lions in a nearby enclosure, and it turned out that the Park also knew all along that the septic tank for the Park’s toilets were leaking through a broken pipe right out into the water next to the dolphin cage. They never admitted to this, but claimed only that dolphins could not possibly be the source and secretly fixed the broken pipes and leaking septic tanks, and then said the algae problem was natural and would go away by itself. But it made no difference afterwards in the amount of algae killing corals for kilometers down-current, since the amount from the dolphins alone were enough to trigger serious algae over-growth. In fact the local divers report that the problem continued to intensify and spread even after the dolphin operators claimed they had solved it. At another site in Cozumel, Punta Langosta, where they put in dolphin pens, slimy bacterial and algal mats that had not been present before grew very rapidly and killed the corals downstream. Before the 2004 hurricane they took the dolphins out and put them into a swimming pool, where many died. The algae then quickly died back as they were no longer over-fertilized. When they fixed the broken enclosures and put more dolphins in again, the slime re-appeared, spread, and killed yet more corals. The 2005 hurricane totally demolished the dolphin pens, and I’m sure that the algae diminished again, at least until they rebuild them. The pattern of algae in space and time indicates that nutrients from the dolphin pens are the only source that could explain this, since the algae march in lock step with the changes in nutrient inputs. That site is immediately downstream from one of the largest cruse ship piers in Cozumel, but I can see no impact from them, and it is clear the ships are not discharging the sewage of their thousands of passengers when they are in port, or I would immediately see the effects on the algae. At the third site I looked at, on Isla Mujeres, the water even upstream from the dolphin pens is highly polluted by untreated sewage effluent from Cancun, and the bottom is covered with algae. But for about a mile on the downstream side from the dolphin pens there are masses of the same kinds of algae that one finds around sewage outfalls, which were not present on the up-current side of the dolphin pens. You can clearly see the same sort of nutrient impact in Grand Cayman by swimming offshore from the turtle farm, or off the garbage dump in North Sound, or in the patches of slimy algae on the bottom sand off the 7 mile beach that reveal exactly where the hotel septic tank effluents are trickling through the rock and sand into the water. Wherever the nutrients are high, the algae will take over, and it is only by controlling and recycling all land-based nutrient inputs, and not adding new ones, that we can keep our reefs safe for corals and local or tourist swimmers. To my surprise, every place I dived around Grand Cayman had too much algae, and it is urgent that the Cayman Government get a handle on controlling the problem before you end up like Jamaica, where the reefs are now almost entirely dead and covered with masses of weeds. One of those planning to bring captive dolphins to Cayman has a dolphin operation in Ocho Rios, Jamaica, where I learned to swim as an infant. At that time we had the most incredible reefs there, the first in the world to be studied by a diving scientist (my father), but they were all quickly killed by uncontrolled development. Now the dolphin operators have no idea what we lost, since there is no longer any trace left of the magnificent reefs except in my memory and my father’s photographs. Ironically, the dolphin operators planning to move to Cayman say that the Ocho Rios site is not polluted, but there the human sewage background has been so high for 50 years that they think getting ear infections is the normal result of swimming in the sea, since nobody is left there who remembers how it used to be. My personal contribution to this issue in Cayman has been to work with the Department of the Environment to become the first place in the tropics to use new state of the art equipment to map the distributions of nutrients directly, in order to measure their impacts on the reefs and seagrasses, track them back to their sources, and plan steps to eliminate them. DOE is highly competent and fully aware of the problem, but they do not yet have the resources for the equipment they need to be on top of it. At present no coastal zone managers anywhere in the world know how many nutrients are flowing into their waters or can remedy them, because they have only the most limited knowledge of the magnitudes, locations, and impacts of the sources. Putting coastal management on a scientific basis will take new approaches that nobody else in the world is yet doing. If Cayman takes the lead, I’m sure many others will follow. I can only hope that DOE gets the funding and political support they need to clean up Cayman’s waters before things get out of control. In my view new sources of nutrients should be prevented until DOE has had the chance to fully assess the existing problems and formulate and apply solutions. Simply fooling ourselves for marketing PR that there are no problems in paradise will only let the cancer spread until it is too late or too expensive to keep Cayman waters clean and blue instead of dirty and green, like so many of your competitors. Sincerely yours, Thomas J. Goreau, PhD President, Global Coral Reef Alliance |
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