Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005very warm ocean surface temperatures, each of the Atlantic hurricanes passed around thisregion. While this absence of storm activity saved the island communities from the potentialdevastation of hurricane landfall, it also removed the ameliorating effects that tropical stormshave for tropical regions.This figure illustrates the named storm tracks (including hurricanes) for 2005. Dottedlines show paths of tropical storms; hurricane strength is shown by the thickness of thesolid lines (3 groups: categories 1; 2 & 3 together, 4 & 5 together). The marked track isof Hurricane Katrina whose storm surge devastated New Orleans. Note the clear regioncentred around 65 o W:20 o N; no hurricanes passed over the very warm waters, whichresulted in massive coral bleaching in the Lesser Antilles . Compare this ‘hole’ with theNOAA thermal stress images on the front cover and on pages 9-11.Th e Go o d a n d t h e Ev i l o f Hu r r i ca n e s f o r Co r a l ReefsWhile there is often a perspective that hurricanes are only destructive and disastrous events,they also provide ecological benefits to tropical and sub-tropical environments. Rainfall givesa boost to wetlands and flushes out lagoons, removing waste and weeds. Hurricane windsand waves move sediment from bays into marsh areas, revitalising nutrient supplies. Whilethere is always the potential for mechanical damage, coral reefs can also receive benefit fromhurricanes during the warm summer months (1.).During the summer hurricane season, as ocean surface waters become warmer, corals oftenexperience thermal stress. Hurricanes can alleviate this thermal stress by three mechanisms.First, as hurricanes absorb energy from surface waters through the transfer of latent heat, thetemperature of the water is reduced (evaporative cooling). The magnitude of the cooling isrelated to the intensity and extent of the hurricane. Second, hurricanes also reduce sea surface34
Hurricanes and their Effect on Coral Reefstemperatures (SST) by inducing local upwelling, bringing deeper, cooler water to the surface.The amount of surface cooling resulting from these mixing mechanisms will depend on thehurricane wind speed and how the water temperature varies with depth at each location.Finally, the clouds of a hurricane shade the ocean surface from solar heating allowing thewater to cool and reducing light stress.The figure on the left shows regions of positive and negative sea surface temperature anomaly withthe track of Hurricane Katrina over the cool wake. The graph on the right is a SST time-series atSombrero Reef, Florida Keys showing the rapid drop in temperature following the passage of hurricanesDennis (D), Katrina (K), Rita (R) and Wilma (W). Hurricane Katrina passed over the FloridaKeys as a Category 1 hurricane on 26 Aug 2005, during the hottest period, reducing the temperaturestress and halting a temperature trajectory towards coral bleaching.While larger, more intense hurricanes provide the greatest cooling near the ocean surface,they are also the most destructive. Waves and water movement significantly influence thestructure and distribution of coral assemblages. Generally, the more delicate ‘branching’corals (e.g. Acropora spp.) are more vulnerable to wave damage than corals with a ‘massive’or ‘boulder-like’ growth form (e.g. Porites spp.). As a consequence, massive corals tend todominate coral communities in areas regularly exposed to oceanic swells, while delicatespecies thrive in low energy areas such as lagoons and back-reef areas (2.). In addition, wavesand tidal water movements scour some areas exposing the solid limestone structure of thereef, which provides a firm foundation on which corals can settle and grow. In other areas,water movement results in the accumulation of sediment and rubble, which is unstable and,therefore, less suitable for coral settlement.The waves generated by hurricanes are larger and more powerful than those experiencedunder normal conditions and can affect all parts of a reef. As a consequence, they are theprimary cause of hurricane-related damage to corals and coral reefs, often breaking coralbranches and overturning colonies. Dislodged coral pieces can cause further damage as theyare propelled onto other parts of the reef. In 2005, Hurricane Rita damaged the deep reefs ofthe Flower Garden Banks, while Wilma scoured the reefs of the Florida Keys.35
Page 1 and 2: Stat u s o fCa r i b b e a nCo r a
Page 3 and 4: Dedication: This book is dedicated
Page 5 and 6: Status of Caribbean Coral Reefs aft
Page 25 and 26: Status of Coral Reefs in the Caribb
Page 35 and 36: 3. Hu r r i ca n e s a n d t h e i
Page 37: Hurricanes and their Effect on Cora
Page 41 and 42: 4. Th e 2005 Bl e a c h i n g Ev e
Page 43 and 44: The 2005 Bleaching Event: Coral-Lis
Page 49 and 50: 5. Stat u s o f t h e Mesoamerican
Page 51 and 52: Status of the Mesoamerican Reef aft
Page 65 and 66: 6. Co r a l Reefs o f t h e U.S. Ca
Page 67 and 68: Coral Reefs of the U.S. Caribbean19
Page 69 and 70: Coral Reefs of the U.S. CaribbeanMe
Page 71 and 72: Coral Reefs of the U.S. Caribbeanwe
Page 73 and 74: Coral Reefs of the U.S. CaribbeanSe
Page 75 and 76: Coral Reefs of the U.S. CaribbeanBl
Page 77 and 78: 7. Th e Effects o f Co r a l Bl e a
Page 79 and 80: The Effects of Coral Bleaching in t
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Status of Caribbean Coral Reefs aft
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9. Th e Effects o f Co r a l Bl e a
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The Effects of Coral Bleaching in S
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10. Ma n ag i n g f o r Ma s s Co r
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Managing for Mass Coral Bleaching:
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Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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