Tom Goreau Speaks at Bahamas National Natural History Conference in Nassau on Guana Cay Reef Data
Tom Goreau Speaks at Bahamas National Natural History Conference in Nassau on Guana Cay Reef Data
Summary of Observations of Sewerpipe Algae at Bakers Bay
January 19 2012
Thomas J. Goreau, PhD, President, Global Coral Reef Alliance
Observations in early January 2012 found massive blooms of “sewage-type” algae smothering beach rock and sand where Baker’s Bay golf course greens lie nearest to the shore of northwestern Guana Cay. The spatial pattern and abundance of algae species clearly indicates excessive levels of fertilizer nutrients leaching from the golf course via groundwater flowing into the coastal zone. Reefs near the golf course show an increase in weedy algae overgrowing and killing corals, and new outbreaks of coral diseases that were not found in earlier surveys. These impacts are only starting: promptly cutting off all sources of nutrients will be needed to save Guana Cay reef from being over-grown and killed by nuisance algae in the coming years. This study is to our knowledge the first to examine direct impacts of golf courses on coastal algae and coral reefs, but such impacts would be much more widely found had they been searched for.
BACKGROUND: NUTRIENTS AND CORAL REEFS
Massive blooms of nuisance algae caused by excessive nutrients are called eutrophication. Coral reefs are the most sensitive of all ecosystems to high concentrations of nitrogen and phosphorus nutrients, because they are overgrown and killed by weedy algae growth at nutrient levels so low that they would not impact any other ecosystem (A. DeGeorges, B. Reilly, & T. Goreau, 2010, Land-sourced pollution with an emphasis on domestic sewage: Lessons from the Caribbean and implications for coastal development on Indian Ocean and Pacific coral reefs, Sustainability, 2: 2919-2949). Coral reefs therefore need the strongest, ecosystem-specific water quality standards to be protected. The currently used standard limits almost everywhere are based on human drinking water quality standards, and we can safely drink water with nutrient levels hundreds of times higher than those which kill coral reefs.
ANY source of excessive nutrients, whether from golf course fertilizers or other sources, is a problem for coral reef habitats. Besides massive growth of algae there is strong evidence at sites with high levels of nutrients of strong local correlation between pollution and coral diseases. For example see footage showing algal blooms killing corals near nutrient sources from dolphin pens in Mexico and intense concentrations of White Plague Disease, the coral disease that kills corals the fastest (corals die at up to 10 cm a day), and which affects most coral species, around the Cayman Turtle Farm effluent in the documentary film by T. Goreau, 2007, Tourism, water quality, and coral reefs.
Nutrients in coastal waters have many sources, including natural nutrients recycled from healthy coral reefs, mangroves, seagrasses, and upwelling of cold deep ocean waters. Along developed coastlines almost all the nutrients come from human sources, and they greatly overwhelm the natural ones. Whenever nutrients are too high, coastal zones are overgrown with nuisance algae, killing corals, and fish and shellfish habitat. As a result development of coastal tourism next to reefs almost inevitably results in the death of nearby reefs, and tourists then must go a long way to see healthy corals and fishes. Along most coastal zones the predominant source of nutrients is human sewage, but in some areas livestock manures and agricultural fertilizers can be the major source. This is no surprise because plants need high concentrations of fertilizers to grow fast, and when these are washed into the sea, they act as fertilizers for marine plant growth. Almost all other elements the algae need to grow are present in excess in the sea, so their growth rates are limited by the least abundant elements they need, which are nitrogen and phosphorus. Very small amounts of these elements, undetectable except with the most sensitive analytical methods, trigger explosive growth of nuisance algae blooms. Of special concern are heavily fertilized golf courses on tropical islands with nearby reefs, and in particular the major fertilizer elements nitrogen and phosphorus.
Because these trace amounts of nutrients are so hard to measure accurately, very few researchers do. Most environmental impact assessments either ignore or discount the effects of nutrients, or use inadequately sensitive methods to claim that they are too low to make a difference, which might be true in any habitat EXCEPT a coral reef. Most environmental impact assessments simply assert there is no possibility of harmful effects on water quality without any measurements at all, and they almost never do before and after studies on the actual ecological impacts of the changes in water quality they cause. Nutrient concentrations will change rapidly due to changes in winds, currents, waves, rainfall etc. so very large numbers of measurements are needed to measure the average concentrations and the range of variability. Since such measurements are very expensive they are almost never done in adequate numbers.
It is much easier to document changes in the algae, because algae grow very fast in response to high nutrients, show very characteristic changes in species dominance under high nutrient conditions, and also visibly show nutrient levels by their color and branching patterns. Algae sit still on the bottom and integrate the changes in the water quality above them, and so provide information on changes in nutrients quickly and clearly that would take vast amount of work to show from direct nutrient measurements. They respond in days to weeks, whereas coral health reflects changes over years. By the time the corals have severely declined it is almost always too late to do anything about it. In contrast, the algae provide an early warning system that is hardly utilized because only a handful of people in the world know the nutrient ecology of the algae well enough to interpret them. Here we use such studies to document changes in water quality caused by golf course nutrient inputs. To our knowledge no one has directly studied such changes before, we have been unable to find any studies that actually examined the impacts of golf courses or tourism developments both before and after development. This makes it easy for developers to claim “there are no studies showing any impacts”. Our Guana Cay work appears to be the first to directly examine such impacts from golf courses.
Coral reefs in the Bahamas are well known to divers to have undergone dramatic declines in recent years, although there is little documentation. E. Pante, A. King, and P. Dustan, 2008, Short-term decline of a Bahamian patch reef coral community: Rainbow Gardens Reef 1991-2004, showed that the reefs of Iguana Cay in the Exumas had coral bottom cover decline from 13% to only 3% over this period. Much of this decline was likely due to the compound effects of global warming and new diseases. Given the overall decline it is important to prevent any additional stresses caused by human activities on the adjacent land. Yet most coral reef researchers “explain” changes in algae purely by changes in algae-eating fish, like parrotfish and surgeonfish, even though they are not eaten in the Bahamas. They blame fishermen for reef decline instead of the real causes, avoiding pressures on developers to reduce nutrient inputs or on policy makers to treat sewage adequately. Studies show that nutrients from land, not algae-eating fish, are the major control over algae abundance (B. E. Lapointe, P. J. Barile, C. S. Yentsch, M. M. Littler, D. S. Littler, & B. Kakuk, 2004, The relative importance of nutrient enrichment and herbivory on macroalgal communities near Norman’s Pond Cay, Exuma Cays, Bahamas: a “natural” enrichment experiment, Journal of Experimental Marine Biology and Ecology, 298: 275-301; C. Mora & R. Ginsburg, 2007, A clear human footprint on the Caribbean coral reefs, Proceedings of the Royal Society of London B, doi: 10.1098/rspb.2007.1472)
Plans for a huge golf course, hotel, houses, and a mega-yacht marina on the uninhabited northwest end of Guana Cay, next to some of the best reefs in the Bahamas, were strongly opposed by the local residents, who are largely traditional fishermen whose livelihood depends on the health of the reef. They appealed for help from scientists to examine the reefs before any development started as there were no previous studies of these sites or their conservation needs.
Three groups of scientists voluntarily came at different times to examine the sites. Dr. Michael Risk of McMaster University studied the area in 2004. Dr. James Cervino of Pace University and the Woods Hole Oceanographic Institution did more detailed work in 2005, 2006, and 2007. Dr. Thomas Goreau looked at these sites in 2007, and again in early 2012 after the golf course had been built. These three researchers independently examined the reefs near the Baker’s Bay development site (Central green X in image below), as well as control sites located both up-current and down-current from it. These include Fowl Cay (Green X at south east), and a site to the Northwest, all at similar depth and exposure. These sites are all regularly used by local dive operators, and observations of changes were made by local divers who go to them frequently.
Construction of the Baker’s Bay development began soon afterwards. By 2009 the entire interior of northern Guana Cay had the vegetation cleared and burned, mangroves were dredged out to form a huge marina, a channel dredged through seagrass to make an entrance to the marina, and the dredge fill dumped on low lying swampy former mangroves as landfill for development. Despite efforts to use silt curtains to contain sedimentation on seagrasses and reefs, these failed to contain the sediment plumes that passed right by the silt curtains and affected nearby habitats. The loss of most of the mangroves on Guana Cay will have long-term impacts on coastal erosion and the elimination of critical nursery habitat for juvenile fishes and lobsters.
The Golf Course was built and the lawns fertilized by 2009, but sale of lots for villas was very slow due to the economic crisis. The result is that to date the development has basically stalled at the Golf Course stage, but no houses have yet been occupied nor have the hotels and marina development opened. As a result there are no permanent inhabitants, just a caretaking staff, so there is essentially no sewage from residents or visitors, nor pollution from the marina, and golf course fertilizer is the only major source of nutrients at present. This site therefore provides an extremely unusual case in which the impacts of the golf course can be examined by itself, without the compounding effects of sewage additions from the development.
Following dredging there was greatly increased turbidity in nearby seagrass areas and coral reefs, but after several years most signs of turbidity have disappeared, because suspended sediments were washed away by wave and current action. The area has a predominant wind-driven current from the east, due to the Trade Winds. The sedimentation therefore acted as a temporary stress whose effect is now basically over, and the impacts on seagrasses and coral reefs do not seem to have been major. Of more concern than a single short-term input of suspended sediments are the long-term consequences of increased nutrient buildup from Baker’s Bay fertilizers and sewage.
CURRENT SITUATION: JANUARY 2012
The best indicator of land based nutrient inputs is growth of weedy algae species along rocky shorelines and beach rock. Local nutrient sources can be clearly identified from buildup of masses of high nutrient-indicating species not seen elsewhere. In such areas large masses of nuisance species found, and they are larger, more intensely branched, and have much darker red or green colors than the same species further away and they are growing much faster where nutrients are highest. For more information and photographs on the effects of localized nutrient inputs on algae see: B. E. Lapointe & B. J. Bedford, 2011, Stormwater nutrient inputs favor growth of non-native macroalgae (Rhodophyta) on Oahu, Hawaiian Islands, Harmful Algae, 10: 310-318
The distribution of algae therefore unambiguously allows local nutrient sources to be identified. We examined algae along the shore around large parts of Guana Cay and nearby islands including Gum Elemi Cay, northwest of Guana Cay, and Scotland Cay, southeast of Guana Cay. The only place found with massive blooms of brightly colored algae indicative of very high levels of nutrients, such as at the end of sewer pipes, was along the shore directly below where the golf course greens most closely approach the shore line just south of the northwest tip of Guana Cay. Where the golf course greens most closely approach the shore there is a bright band of intensely green and red algae along the beach rock and sand in front of it, visible in this photo as the dark line in front of the sand that is underwater in this high tide photo. At low tide the algae reaches the water line. The abundance of algae decreases away from the shoreline. Note that the golf course greens are directly above the shoreline with little or no buffer zone or vegetation barrier. Video of algae at this site can be seen at here:
The algae in front of the golf course are dominated by brightly colored green clumps of Enteromorpha flexuosa. These are intense dark green, tall and densely branched, while the same species found at other sites were pale yellowish or brown and low growing. Another nutrient indicating green alga present in smaller amounts is Anadyomene stellata. The fleshy red algae are also intensely pigmented, tall, and bushy, indicating very rapid growth. About 10 species of nutrient-indicating fleshy red algae are abundant including Heterosiphonia, Ceramium, Centroceras, Wrangelia, Dasya, Chondria, Bryothamnion, Digenia, Laurencia, and Polysiphonia. Cyanobacteria mats are seen on the sand and beach rock directly where the groundwater drains through the sand into the water from the golf course greens above them. These weedy algae diminish rapidly and are found only as small, pale and low lying colonies as one moves away from the golf course on either side or away from the shore. These results confirm that there is intense leaching of weedy algae-promoting nutrients from the golf course areas only. It should be noted that since these measurements were made near the coldest time of year, the driest time of year, and after a period of rough weather, the algae abundances were near their annual low. Higher abundances are expected when the hot and rainy season comes.
The shoreline around the harbor with the highest population density in Guana Cay shows a coating of green algae all over the rocks, but this was a very low turf and was not bright green in color as it would have been if it were rapidly growing and well fertilized, instead appearing more yellow-green or brown. This suggests that it had grown rapidly in the warm, rainy summer season and was currently dying back or senescent. The source of these nutrients is unquestionably from soak away toilets on the island. But the impact was limited to the harbor itself and did not show up outside the harbor mouth.
On Scotland Cay, which has a far lower population density, largely short-term visitors rather than permanent residents, the harbor was free of signs of weedy algae turf. The same was true of the Baker’s Bay Marina. Both the interior walls of the dredged out marina and the rock walls lining the channels to it were free of weedy algae, indicating that there is no significant source of nutrients in the marina area itself.
CURRENT SITUATION: JANUARY 2012
In 2010 an intense outbreak of White Plague disease was noted at the reefs of North Guana Cay near the golf course, with around 20 cases seen in areas where previously only one case had been seen. This disease kills corals the fastest, up to 10 cm per day, and affects the most species. The disease spread quickly during the warm summer temperature season, but then stopped when temperatures dropped for the winter season, as has been seen elsewhere in the Caribbean. When temperatures warmed up in 2011 White Plague reappeared, causing more coral mortality and again stopped when winter came. Observations in January 2012 found that even though active phases of White Band had gone dormant for the winter on all the massive corals, about 15 cases of active White Plague were seen, almost all on Agaricia agaricites and a few on Agaricia tenuifolia. Several cases of Dark Spot disease were seen on Siderastrea siderea and Stephanocoenia intersepta. One case of Yellow Band was seen. What may be a new disease was seen attacking the top of one large Montastrea annularis. In sharp contrast, at the downstream site only a single case of Dark Spot (on Agaricia agaricites) was seen and in the upstream site a single case of Black Band (on Diploria strigosa) was seen, and no cases of active White Plague.
CURRENT SITUATION: JANUARY 2012
The summer seasons of 2010 and 2011 were also distinguished by large increases of algae growth, which also largely disappeared in the cool season. However in January 2012 we noted around 20 cases of corals being overgrown by weedy algae from the base, largely caused by increases in several species of the fleshy brown alga Dictyota, something that had not been common before golf course development. An unusual prevalence of the clumps of the fleshy red alga Martensia pavonia was noted. More alarming was a rapid proliferation of slimy cyanobacteria mats on corals, gorgonians, sea fans, and on sediment. Cyanobacteria are classic indicators of high nutrient levels on coral reefs, for example around sewage outfalls, and tend to expand in the warm season and during the rainy season when more nutrients are flushed from land. Fish will not eat them because many contain toxic compounds. At the time of observation diseases and algae were at the minimum level due to low temperatures, and many algae had been washed away by rough weather, but the impacts were still clearly noticeable. It is anticipated that all of these problems will accelerate on the reef next spring when water temperatures rise.
In contrast to the sites near the golf course, the remote sites had far less algae problems. The downstream site was free of high nutrient-indicating algae species, being dominated by low to moderate nutrient-indicating brown algae and calcareous (sand producing) green and red algae species. The upstream site had moderately high algae abundances dominated by low to moderate nutrient-indicating brown and calcareous green calcareous algae, but the high nutrient indicating species like cyanobacteria and fleshy green and red algae were absent except overgrowing the sand bottom at the spots where tourist boats anchor and where fish feeding activities are focused. However the brown algae were not dominated by Dictyota species as at the down-current site but by Lobophora variegata, a species that in the neighboring Turks and Caicos Islands is an indicator of deep-water upwelling nutrients. Lobophora increased in abundance offshore towards the shelf edge. Therefore a major source of nutrients at this site appeared to be largely from offshore upwelling, rather than from nearby populated areas of Man O’War Cay, Hopetown, and Marsh Harbour. This is significant because this site is downstream from and much closer to the populated areas than any of the other sites, so if sewage were the main cause of algae causing nutrients it should have the most nutrient-indicating algae.
CONCLUSIONS AND RECOMMENDATIONS
The result of these algae and disease outbreaks has been a clear decline in coral health as shown by a decrease in live coral cover to around 30% and a clear increase in partially dead and newly killed corals. This is of serious concern because the reefs of the area are still some of the best remaining in the Bahamas, and they also have very high coral species diversity. Particularly noticeable is the large numbers of young corals of species that are fairly rare in the Caribbean, and a large diversity of colors and forms of Diploria, Mycetophyllia, Agaricia, Leptoseris, Isophyllia, Isophyllastrea, and Manicina corals. Continued algae growth will suppress new coral settlement, since coral larvae need clean limestone to attach themselves. This is a site with high coral diversity that needs to be protected and allowed to recover.
These observations provide unambiguous evidence of high nutrient inputs from the golf course to the near-shore waters, with strong negative impacts on water quality and environmental health, along with strong indications that the effects are spreading to the coral reefs offshore. These impacts are only starting and are still fairly localized, but will increase if the input of nutrients continues, threatening the coral reef itself. Despite the absence of previous studies that specifically examined impacts of golf course nutrients in coral reefs areas, it has been long known that this was a potential risk factor for reefs. Previous golf courses took no precautions to prevent nutrient runoff, and as these effects were also confounded by sewage inputs from adjacent hotels, villas, and tourism developments, there was ambiguity about potential sources that are not present in this case.
It must be pointed out that Baker’s Bay, sensitive to widespread public criticism that a golf course next to a coral reef would threaten the health of the corals, made unusual and unprecedented plans to minimize such impacts, and they should be commended for making such efforts part of their strategic environmental management plan, as they are the first to do so in the Bahamas (K. Sullivan-Sealey & N. Cushion, 2009, Efforts, resources and costs required for long-term environmental management of a resort development: the case of Baker’s Bay Golf and Ocean Club, the Bahamas, Journal of Sustainable Tourism, 17: 375-395). Previous developers made no such efforts and none were held to account for the damages that certainly must have resulted as no effort was made to identify such impacts. Baker’s Bay promoted a higher standard, as is needed in all future developments. Baker’s Bay announced that the greens would be sloped inward so all drainage would flow inland to a site where it could be pumped and treated or reused for irrigation, that the greens would be lined with an impermeable barrier layer underneath that would prevent leaching of fertilizers into the groundwater, and that they would maintain a wide buffer zone of vegetation to absorb any runoff (L. Marshall, personal communication).
Unfortunately these guidelines to minimize impacts do not appear to have been followed at the northwest tip of the island. The golf course greens lie in places just inland from the shoreline, are 5 to 10 feet higher than the water level so there is clear downward gradient of groundwater flow, and the vegetation barrier is totally absent or very sparse in many places. Where the lining could be seen from the beach there was only one short spot of a couple of feet that had an impermeable rubber barrier, but more than 95% of the visible liner was an open permeable mesh that retains sand but allows rain and ground water runoff to pass right through it.
The only solution to this problem is to rapidly cut off the supply of nutrients. Weeding the algae is a fool’s errand because it grows right back due to high nutrient inputs. The only known way to get rid of weedy algae is to totally cut off the excess nutrient inputs. This has only been accomplished successfully long-term in one place in the world, Dragon Bay in Jamaica. Within weeks of the land-based nutrient inputs being cut off the algae began to turn pale and die back, and within two months they were gone, the algae covered limestone turned clean again, and corals began to settle on them: T. Goreau, 2003, Waste Nutrients: Impacts on coastal coral reefs and fisheries, and abatement via land recycling, 28p., UNITED NATIONS EXPERT MEETING ON WASTE MANAGEMENT IN SMALL ISLAND DEVELOPING STATES, Havana, Cuba
Implementing this will not be easy unless the golf courses are redesigned to avoid all groundwater leaching into the sea, and fertilizer use reduced to a minimum. Fertilizers are typically applied in excess of the capacity of the plants to take it up, so most ends up polluting groundwater and near-shore waters. In addition most fertilizers only provide nitrogen, phosphorus, and potassium, but these limestone soils are also deficient in many other minerals. Insufficient supplies of the other limiting mineral elements prevent plants from taking up the nitrogen and phosphorus efficiently, thereby increasing losses and pollution.
Rapid action is needed. The situation would be far worse if the original development plans had resulted in operational hotels, marinas, and residences because then the impacts would have been compounded by sewage inputs. The first author has seen coral reefs in Jamaica killed in a few years when similar weedy algae, which were at first confined to the shoreline next to local nutrient inputs, rapidly spread outward and smothered entire coral reefs as development increased (T. J. Goreau, 1992, Bleaching and reef community change in Jamaica: 1951-1991, in SYMPOSIUM ON LONG TERM DYNAMICS OF CORAL REEFS, AMERICAN ZOOLOGIST, 32: 683-695). In 1991 he did a study of algae on the South Pacific island of Moorea. At that time nuisance algae were confined to the immediate vicinity of sewage outfalls. Three years later he found that the entire lagoon and reef was smothered in weedy algae. This should not be allowed to happen to some of the Bahamas’ best remaining coral reefs.
Although fertilizer runoff from golf courses is often mentioned as a development concern, to our knowledge this is the first study to directly examine the effects of golf course runoff on coastal algae and coral reefs before and after development. R. H. Richmond, 1993, Coral reefs: Present problems and future concerns resulting from anthropogenic disturbance, American Zoologist, 33: 524-536 says “Golf course construction on tropical islands has increased at an alarming rate in the past few years, considering the size of the land masses involved, the quantity of pesticides and fertilizers used, and the fresh water requirements for maintain greens and fairways.” However he discussed only the potential for soil and pesticide runoff and made no field observations. S. J. Dollar & M. J. Atkinson, 1992, Effects of nutrient subsidies from groundwater to nearshore marine ecosystems off the island of Hawaii, Estuarine, Coastal, and Shelf Science, 35: 409-424 concluded that fertilizer leaching should increase nutrient flows to the sea up to around 2 to 6 times, but claimed that the groundwater would float on top of the ocean and would not affect the algae growing on the bottom at all, and that phytoplankton (floating microscopic algae) would increase no more than 2%. Their conclusions were based on a mathematical model and not on field observations. S. J. Dollar & R. W. Grigg, 2004, Anthropogenic and natural stresses on selected coral reefs in Hawaii: A multidecade synthesis of impact and recovery, Pacific Science, 58: 281-304 examined reefs in front of three bays with golf courses, resorts, community sewage, and pineapple plantations. They concluded that reefs in Hawaii were in good condition and not affected by declines seen elsewhere in the world, that the major stress was wave energy, but that reefs in the bays were affected by sediment runoff from the bare soil in pineapple plantations causing coral smothering by mud, and that these were episodic and not progressively increasing stresses. They did not examine the algae. P. L. Jokiel, 2006, Impact of storm waves and storm floods on Hawaiian reefs, Proceedings of the 10th International Coral Reef Symposium, 390-398 mentions massive erosion of soil from land just graded for a golf course that smothered an offshore reef, but this was before the greens were planted or fertilized. E. Derse, K. L. Knee, S. D. Wankel, C. Kendall, C. L. Berg, & A. Paytan, 2007, Identifying sources of nitrogen to Hanalei Bay Kauai, utilizing the nitrogen isotope signature of macroalgae, Environmental Science and Technology, 41: 5217-5223 measured nitrogen isotopes in algae and concluded that almost all of it came from fertilizer, but were not able to pinpoint whether golf courses or farms were the source.
Because of the large number of golf courses already built and planned for the future in the Bahamas and other islands, there is a critical need to examine these for impacts on coastal and reef algae. We feel that such impacts are likely to be found wherever people actually look for them. The lack of such studies has been used by developers to claim that there is no impact, but that is simply because prior to our study, nobody seems to have looked. Absence of evidence is not evidence of absence.
Only one country in the world, the Bahamas’ closest neighbor, the Turks and Caicos Islands, has a policy that all developers must not only build a secondary sewage treatment plant, they must also recycle all the nutrient rich waste water as irrigation on their own property in order to absorb the nutrients by the vegetation and prevent contamination of the groundwater and coastal zone. TCI is also the first country to adopt coral reef-specific water quality standards for discharges to the coastal zone. The Bahamas urgently needs to learn from their brothers to the east in order to protect their own coral reefs and fisheries. And the lessons learned in Guana Cay need to be applied throughout the Bahamas and coral reef regions to prevent similar damage from similar proposed large developments elsewhere.
We thank Dr. Michael Risk for discussions of his previous observations, Stephen Jenkins for photographs, the staff of Dive Guana for assistance with boats, tanks, and dive gear, and the Guana Cay community for their kind hospitality.