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 EventBarbadosIn t r o d u c t i o nBarbados is the most easterly of the Lesser Antilles island chain. The uplifted fossil coralisland is surrounded by a 2-3 km wide shelf that supports a variety of coral reefs. Fringingreefs distinguish the west (leeward) coast and make up 8.4% of the mapped reefs; beyond thatthere is an almost continuous bank reef parallel to the north, west and south coasts 0.5 to 1.2km offshore. The crest of this bank reef is 5-35 m deep in the north, west and south and isshallower along the more exposed southeast coast, where it becomes a bank barrier reef. Thisbank contains 87.1% of the mapped reefs. There are also a few patch reefs at 5-16 m depthbetween the shore and the bank reef, along the west to southeast coasts.Stat u s o f Co r a l Reefs Pr i o r to 2005The inshore fringing reefs have been affected by poor water quality caused by coastal construction,tourism infrastructure and inland agriculture; by storms; and by over-exploitation of fish andcorals. Average live coral cover is about 10% in the seaward spur and groove zone (range1-30%). The offshore bank reefs are relatively undamaged with about 30% coral cover alongthe crest. These bank reefs are far enough offshore to escape damage from poor water quality,and are also less accessible to fishers. The patch reefs are more variable; they are dominatedby hard corals and sponges on the west coast, and soft corals on the more exposed windwardcoasts, although hard coral cover averages 25%. There have been infrequent bleaching eventsin south-eastern Caribbean islands; most have occurred within the last decade but were usuallyof low to moderate intensity.Effects o f t h e 2005 Bl e a c h i n g Ev e n tNOAA satellite sea surface temperature (SST) data for the eastern Caribbean, including Barbados,showed a coral bleaching ‘HotSpot’ (SSTs in excess of 1 o C above the maximum expectedtemperatures) that developed to the northeast of Barbados in early June, and strengthened inJune-July to cover Barbados and the Lesser Antilles by early August. The HotSpot strengthenedduring August and September and covered much of the Caribbean Sea by early October. Itfinally disappeared in late October.Sea temperatures at 8 m depth on a shallow patch reef confirmed the satellite data, withdaily mean temperatures climbing steadily from 28.6 o C in late June to more than 30 o C in lateAugust and early September. This was 1-2 o C above the ‘typical’ summer maximum. During thesecond and third weeks of September, strong currents brought cooler water onto the reefs andreduced temperatures by almost 1.5 o C, before they returned again to 30 o C for the last week ofSeptember. Sea temperatures declined to 29.3 o C by the end of October and to 28.6 o C by theend of November. Benthic temperature loggers at 20 m depth on other sites showed similartemperature patterns to those reported by research divers and dive operators, with widespreadwarm waters extending to at least 30 m depth.97
Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 200530.50Batts Rock30.00Temperature ( C)o29.5029.0028.5028.0027.5028/6/055/7/0512/7/0519/7/0526/7/052/8/059/8/0516/8/0523/8/0530/8/056/9/05Date13/9/0520/9/0527/9/054/10/0511/10/0518/10/0525/10/051/11/058/11/0515/11/0522/11/05An automatic temperature recorder placed on Batts Rock in 2005 showed that water temperaturesrose above the normal bleaching threshold of 29 o C in mid-year and continued until late October.Additional temperature recorders paced at North Bellairs, Coconut Court and Atlantis showed thatthese sites had a similar temperature profile to that of Batts Rock, with a characteristic declineof almost 1.5 o C during the second and third weeks of September caused by strong currents thatbrought cooler water onto the reefs before returning again to 30 o C in the last week of September. Suchprolonged hot water stress had never been recorded previously in Barbados.The accumulated heating stress was severe for the eastern Caribbean including Barbados, withDegree Heating Weeks (DHWs) exceeding 5 for much of the summer and reaching a maximumof 13-14 weeks by the end of October and beginning of November 2005.The first bleached corals were noticed on 24 August at Batts Rock (8 m depth), where severalcolonies of Siderastrea siderea were a pale mauve/blue color. Two days later, similar bleaching ofS. siderea was seen at 16-20 m depth on the Atlantis bank reef, as well as colonies of Meandrinameandrites and the fire corals (Millepora spp.). By 3 September, bleaching affected coloniesof Dendrogyra cylindrus and Porites astreoides, and some colonies of Montastraea annularis.By mid-September there was widespread bleaching of whole coral colonies in all reef habitatson the west and southwest coasts of Barbados. Dive operators, charter boat captains, fishersand the public reported bleaching. Surveys of 6 reef habitats between mid-September andOctober 2005 showed severe coral bleaching in all reef habitats, with 59-86% of all hard coralcolonies showing some bleaching. Inshore reefs were more severely affected (80.6% of coloniesbleached) than offshore reefs (60.5%).Bleaching also affected 90% of the 29 coral species, with some species being more vulnerablethan others. Among the more common species, the most susceptible to bleaching were D.cylindrus, Agaricia spp., Favia fragum and Millepora complanata, with 90% or more ofcolonies affected, whereas fewer than 10% of colonies of Colpophyllia natans and Madracisdecactis bleached. More colonies of Diploria strigosa and P. astreoides bleached on shallowreefs than on deeper reefs, while the converse was true for S. siderea.98
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Stat u s o fCa r i b b e a nCo r a
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Dedication: This book is dedicated
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Status of Caribbean Coral Reefs aft
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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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Hurricanes and their Effect on Cora
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Hurricanes and their Effect on Cora
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4. Th e 2005 Bl e a c h i n g Ev e
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The 2005 Bleaching Event: Coral-Lis
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Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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