Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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Status of Coral Reefs of the Lesser Antilles after the 2005 Coral Bleaching EventA mix of fringing and barrier reefs grow on the narrow shelves surrounding Guadeloupe andMartinique. These are similar to reefs growing around high islands in the Eastern CaribbeanStates with better development on the windward coasts of the islands, but greater biodiversityon the protected leeward coasts. There are 4 marine reserves: 2 in Guadeloupe; 1 each in St.Barthélemy and St. Martin; and 9 no-take zones in Guadeloupe and Martinique.Saint-Barthélemy and Saint-Martin are the northern-most islands in the FWI, situated on ashallow, sediment covered shoal. Saint-Barthélemy is surrounded by numerous small islands,and Saint-Martin/Sint-Maarten is under French and Dutch control. There are poorly developedfringing reefs and extensive seagrass beds around both islands, and large areas of mangroveshave been destroyed by land reclamation.Stat u s o f Co r a l Reefs Pr i o r to 2005There is very clear evidence of coastal ecosystem degradation throughout the FWI, whichhas affected coral reefs, seagrass beds and mangroves. Long-term monitoring since 1999has shown that the coral communities of Guadeloupe and Martinique have been degraded,particularly during the last 7 years, confirming qualitative observations since the early1980s. High rainfall, deforestation for agriculture, poorly managed coastal development andmangrove clearing have resulted in excessive sediments and nutrients flowing into coastalwaters, especially into enclosed bays and lagoons. Elevated nutrient loads from overuse offertilizers and poor wastewater treatment have fueled the proliferation of algae, particularlySargassum and Turbinaria on the exposed outer slopes on the Atlantic coasts, and Dictyota onmore sheltered areas in lagoons and reefs on the Caribbean coasts. Turbinaria and Sargassumare highly resistant to waves generated by hurricanes, whereas Dictyota is removed by eachpassing hurricane, although it recolonizes reefs rapidly after storms. Chronic over-fishing hasreduced fish stocks, particularly herbivorous fish that control algal communities.Previous coral bleaching from elevated sea surface temperatures (SST) during El Niño years in1984 and 1987 was relatively minor. The first significant bleaching occurred in September andOctober 1998, when the SSTs exceeded 29°C for several weeks. There was extensive bleachingof hard corals, actinarians, zoantharians and gorgonians. Although these reefs suffered somemortality among certain corals, the effects of bleaching in the FWI were relatively smallcompared with other regions in the Caribbean. Bleaching occurred again in 1999 in Guadeloupe,but the effects of bleaching were obscured by damage caused by Hurricane Lenny. FWI reefsshow chronic but minor bleaching almost every year in September when SSTs exceed 29 o C fora short period.The waves generated by hurricanes limit coral reef growth in the Lesser Antilles, and severehurricanes cause serious damage to coasts every 10 years on average. Direct physical damage tocoral reefs occurs to 15 m depth and recovery can take years to decades. Hurricanes are usuallyaccompanied by torrential rains that wash massive quantities of sediments and nutrientsonto nearshore reefs, resulting in short-lived algal blooms. Since 1989, there have been 4hurricanes that have directly damaged the FWI: Hurricane Hugo (1989) hit Guadeloupe; andSaint-Barthélemy and Saint-Martin were damaged by Hurricanes Luis and Marilyn in 1995,and Lenny in 1999, which also caused damage to Guadeloupe.87
Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005Guadeloupe: The first signs of reef decline were evident in the 1980s, and by 2000, satelliteremote sensing showed that only 15-20% of the marine habitats in Guadeloupe still hadhealthy coral communities. Coral cover varied from 15-22% on reef flats; and 24-26% on outerslopes before 2005. The proportion of coral colonies showing disease ranged from 23-33%,with the average surface area of dead tissue ranging from 27-32%. Algal turf was the dominantcomponent of the benthic community, but the greatest changes were in the cover of brownmacro-algae, which were influenced by nutrient concentrations, seasonal temperature changesand wave action. The increase in macro-algae was also favored by the decline in sea urchinpopulations during the early 1980s and over-fishing of herbivorous fish.The reefs of Guadeloupe were not severely damaged by previous coral bleaching, although56% of corals bleached in 1998, with up to 80% of the surface area of colonies being pale.There was, however, little mortality except among colonies of Diploria labyrinthiformis,which suffered 80% mortality. Another bleaching episode that was confined to the reefs ofGuadeloupe occurred in September 1999, affecting almost 50% of corals. Subsequent mortalitywas negligible because the passage of Hurricane Lenny in November 1999 cooled the watersand allowed corals to recover.In 1989, Hurricane Hugo destroyed branching corals (Acropora palmata, A. cervicornis,Madracis mirabilis) on the outer reef slopes down to depths of 15 m. The A. palmata stands,which were prominent on the outer reef slopes, have not recovered but Madracis mirabilis hasquickly recolonized the area. Hurricanes Luis, Marilyn and Lenny damaged Guadeloupe’s coralreefs more severely than Hugo, mainly because large waves up to 13 m high destroyed corals,sponges and gorgonians down to 25 m depth. This damage was compounded by torrential rainsand extensive soil erosion. The high diving pressure on these reefs causes additional damage,particularly from inexperienced divers, especially on the Ilets Pigeon, which receives between80-100,000 divers annually.Surveys at Guadeloupe in 2000 recorded 228 fish species in 59 families, with the average fishdensity between 119 and 550 fish per 600 m 2 . The highest numbers were in the protectedarea of Pigeon Island. The fish biomass in Guadeloupe and the other islands was 368 to1893kg. ha -1 . In 2004, the average number of fish species in 600 m 2 areas was 45 and the average fishbiomass in Guadeloupe was 807 kg.ha -1 , indicating that fish communities have not changedsignificantly in recent years. However, fish stocks around all the islands are over-exploited andlarge fish (groupers, snappers, parrotfish) are rarely seen. Most fishing is artisanal with 1200registered fishers, working from 947 fishing boats that are generally small (6-8 m long) andoperate in inshore waters. Only 10 boats are equipped to operate offshore. There are however,about 1000 unregistered fishers who fish regularly. About 40,000 Caribbean traps are used,with many of these traps being ‘lost’ after each hurricane. However, those traps with wire orplastic netting continue to catch fish long after they are lost.Martinique: Coral cover in 2004 varied between 32% and 40% on various reefs. The dominantcover type was algal turf followed by brown macro-algae, indicating that nutrient pollutionfrom the land is affecting the marine environment. The increase in brown macro-algal coveris a major factor contributing to the deterioration of the reefs. The proliferation of macroalgaewas first noticed on the Atlantic coast in the early 1980s, coinciding with the massmortality of the herbivorous sea urchin Diadema antillarum. Since 1984, macro-algae,particularly Sargassum, have become abundant along the Caribbean coast, probably because88
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Dedication: This book is dedicated
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Status of Coral Reefs in the Caribb
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3. Hu r r i ca n e s a n d t h e i
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Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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