Spatial pattern of coral diversity in Luhuitou fringing reef, Sanya, China

84 quadrats from 5 vertical transects of Luhuitou fringing reef are investigated in detail by using video-quadrat and indoor-interpretation methods. The results show that (1) the reef consists of 69 species of hermatypic corals belonging to 24 genera and 13 families which are unevenly distributed in abundance. (2) Among all the corals, Porites lutea is the most dominant species with importance value percentage up to 36.62%; Porites and Acropora are dominant genera with importance value percentages 43.85% and 22.88%, respectively. (3) There exist distinct spatial differences in coral communities. Both the coral covers and coral diversity indices on the northeastern transects are higher than those on the central and southern transects. (4) Coral communities also show remarkable zonal characteristics with less coral species occurring on reef flat than on reef slope. The importance value percentage of the sole dominant coral genus, Porites, is over 50%, while on the reef slope, the importance value percentages are 28.33% for the first dominant genus Acropora and 26.71% for the second dominant genus Porites. Our further analysis suggests that the spatial and zonal differences of coral diversity pattern are correlated with both natural environmental changes and human activities. The shallow water reef flat is frequently exposed at low tide and it receives more anthropogenic influences (including dredging and trampling) than the deep water reef slope. Thus, the coral community on the reef flat is not as well developed as that on reef slope. The relatively poor coral covers and coral diversity indices on the central and southern transects are closely related to heavy human activities around these sites such as aquaculture, fishing and coastal sewage drainage. Therefore, the impact of human activities must be taken into account in developing strategies for the protection of this coral reef.     

Characterization of geographically distinct bacterial communities associated with coral mucus produced by Acropora spp. and Porites spp

Acropora and Porites corals are important reef builders in the Indo-Pacific and Caribbean. Bacteria associated with mucus produced by Porites spp. and Acropora spp. from Caribbean (Punta Maroma, Mexico) and Indo-Pacific (Hoga and Sampela, Indonesia) reefs were determined. Analysis of pyrosequencing libraries showed that bacterial communities from Caribbean corals were significantly more diverse (H', 3.18 to 4.25) than their Indonesian counterparts (H', 2.54 to 3.25). Dominant taxa were Gammaproteobacteria, Alphaproteobacteria, Firmicutes, and Cyanobacteria, which varied in relative abundance between coral genera and region. Distinct coral host-specific communities were also found; for example, Clostridiales were dominant on Acropora spp. (at Hoga and the Mexican Caribbean) compared to Porites spp. and seawater. Within the Gammproteobacteria, Halomonas spp. dominated sequence libraries from Porites spp. (49%) and Acropora spp. (5.6%) from the Mexican Caribbean, compared to the corresponding Indonesian coral libraries (<2%). Interestingly, with the exception of Porites spp. from the Mexican Caribbean, there was also a ubiquity of Psychrobacter spp., which dominated Acropora and Porites libraries from Indonesia and Acropora libraries from the Caribbean. In conclusion, there was a dominance of Halomonas spp. (associated with Acropora and Porites [Mexican Caribbean]), Firmicutes (associated with Acropora [Mexican Caribbean] and with Acropora and Porites [Hoga]), and Cyanobacteria (associated with Acropora and Porites [Hoga] and Porites [Sampela]). This is also the first report describing geographically distinct Psychrobacter spp. associated with coral mucus. In addition, the predominance of Clostridiales associated with Acropora spp. provided additional evidence for coral host-specific microorganisms.     

Coral and sandstone reef-habitats in north-western Sri Lanka: patterns in the distribution of coral communities

Coral and sandstone reefs cover a significant part ofSri Lanka‘s continental shelf and contain incomparison unique reef structures. Despite this, reefsin this region of the northern Indian Ocean havereceived little research attention. In an attempt tobetter understand these ecosystems and their innatecharacter, this study describes the variety of reeftypes and habitats that are found in this area. Thestudy concentrated on four major reef areas: the BarReef Marine Sanctuary (BRMS), Kandakuliya Reefs,Talawila Reef, and Mampuri Reef. These reefs showedapparent differences in habitat structure in terms ofthe proportion coral cover, coral species compositionand structural complexity. Two reef types were presentwithin the continental shelf of BRMS: coral andsandstone patch-reefs. Acropora was the mostdominant coral genera however in total 118madreporarian species and 50 coral genera wererecorded in the sanctuary. Distinct habitats wereidentified within reef types including shallow reefflat, shallow patch reef, deep reef flat and Porites dome habitats for the coral-reef patcheswhile the sandstone-reef patches were divided intostructured and flat sandstone reef habitats.Kandakuliya Reef south of BRMS was by large dominatedby coral rubble. Talawila Reef and Mampuri Reef showedunique structures with the former being dominated bymassive corals and the latter mainly containingsandstone structures. In addition to factors such asbio-erosion, sedimentation, hydrodynamics, andrecruitment or colonisation processes, some reefs wereclearly under significant direct human impact whichappeared to play a dominant role in habitatstructuring. However, type and degree of humandisturbance varied among the reefs. Habitat alterationat Kandakuliya Reef was the result of intense fishingusing destructive fishing methods. Talawila Reef andMampuri Reef was also influenced by fishing activitiesthough reef structure seemed less affected. This revised version was published online in July 2006 with corrections to the Cover Date.     

Metal levels associated with tin dredging and smelting and their effect upon intertidal reef flats at ko phuket,Thailand

Summary Reef flats in the vicinity of tin dredging and smelting activities around the Laem Pan Wah peninsula, Phuket, and been quantitatively surveyed. the diversity of corals on all intertidal reefs was low (10 genera), the dominant genera being Porites, Montipora, Acropora and Platygyra. Two basic types of reef can be discerned, one dominated by Porites lutea and faviid species and the other by Montipora ramosa and Acropora aspera, reef type apparently being governed by the degree of exposure to water movement. Other natural factors affecting coral cover included freshwater run off, considerable sedimentation, and aerial exposure for 2–3 h each day. Heavy metal concentrations in invertebrate species such as the oyster Saccostrea, the bivalve Isognomon, and in the alga Padina reflected elevated metal levels at all sites when compared with controls (Figs. 8 and 9). In particular, levels of metals were considerably elevated in molluscs taken from the reef below the tin smelter. Interestingly, dead coral cover on this reef, although high, was not significantly different from values observed on reefs several kilometres away from the smelter, which were not apparently under the influence of such increased metal loads (Fig. 2).No elevation in metal concentrations in coral tissue or skeleton was evident at any site. It would appear, then, that these intertidal coral species are not obviously affected by the levels of metals discharged at the smelter site.     

Diversities of coral-associated bacteria differ with location, but not species, for three acroporid corals on the Great Barrier Reef

Patterns in the diversity of bacterial communities associated with three species of Acropora ( Acropora millepora, Acropora tenuis and Acropora valida ) were compared at two locations (Magnetic Island and Orpheus Island) on the Great Barrier Reef to better understand the nature and specificity of coral–microbial symbioses. Three culture-independent techniques demonstrated consistent bacterial communities among replicate samples of each coral species, confirming that corals associate with specific microbiota. Profiles were also conserved among all three species of Acropora within each location, suggesting that closely related corals of the same genus harbor similar bacterial types. Bacterial community profiles of A. millepora at Orpheus Island were consistent in samples collected throughout the year, indicating a stable community despite temporal changes. However, DGGE and T-RFLP profiles differed on corals from different reefs. Nonmetric multidimensional scaling of T-RFLP profiles showed that samples grouped according to location rather than coral species. Although similar sequences were retrieved from clone libraries of corals at both Magnetic and Orpheus Island, differences in the relative dominant bacterial ribotypes within the libraries drive bacterial community structure at different geographical locations. These results indicate certain bacterial groups associated specifically with corals, but the dominant bacterial genera differ between geographically-spaced corals.     

Coral reefs of Bocas del Toro, Panamá: IV. Distribution, structure and conservation state of continental reefs of Peninsula Valiente]

This is the fourth and last contribution describing the individual structure, distribution and conservation status of coral reefs in the Province of Bocas del Toro. Here we describe 14 new reefs along 129 km of coast from Peninsula Valiente to Río Calovébora. Average live coral coverage for this region was 17.1% (+/- 3.6%), mainly in the western region of the peninsula (Bahia Bluefield and Ensenada Tobobe). Coral cover increases with depth (> 5 m) for most species at several reefs and the corals Porites furcata and Acropora palmata dominated shallow waters. Acropora palmata was found abundant in 43% of the studied reefs and toward the regions of the Ensenada Tobobe and Punta Valiente. Coral recruitment rates were similar in distribution to those reefs with greater coral coverage, with average densities of 4 recruit/m2 (maximum 9 recruits/m2) and mainly Agaricia spp., Porites astreoides and Siderastrea siderea. The greater diversity of corals and sponges was recorded toward the western side of the peninsula, with a total of 55 coral species in the study area, including two new records for Bocas del Toro (59 species in total), Dichocoenia stellaris and Madracis luciphila and increasing the diversity of corals of Panama to 65 species. We found 24 species of octocorals and Gorgonia mariae, Muriceopsis sulphurea and Muricea laxaoosens, are informed for the first time to the area, increasing in 10% the diversity for Bocas del Toro (32 in total). We recorded 48 sponges, including five new species for the area and representing an increase of 9% in the total number (58). Large populations of Acropora palmata were found in the Ensenada Tobobe, what justifies once again the need for modifying the existing protected area, so that this new region is incorporated within the conservation plans.     

Linking Demographic Processes of Juvenile Corals to Benthic Recovery Trajectories in Two Common Reef Habitats

Tropical reefs are dynamic ecosystems that host diverse coral assemblages with different life-history strategies. Here, we quantified how juvenile (<50 mm) coral demographics influenced benthic coral structure in reef flat and reef slope habitats on the southern Great Barrier Reef, Australia. Permanent plots and settlement tiles were monitored every six months for three years in each habitat. These environments exhibited profound differences: the reef slope was characterised by 95% less macroalgal cover, and twice the amount of available settlement substrata and rates of coral settlement than the reef flat. Consequently, post-settlement coral survival in the reef slope was substantially higher than that of the reef flat, and resulted in a rapid increase in coral cover from 7 to 31% in 2.5 years. In contrast, coral cover on the reef flat remained low (~10%), whereas macroalgal cover increased from 23 to 45%. A positive stock-recruitment relationship was found in brooding corals in both habitats; however, brooding corals were not directly responsible for the observed changes in coral cover. Rather, the rapid increase on the reef slope resulted from high abundances of broadcast spawning Acropora recruits. Incorporating our results into transition matrix models demonstrated that most corals escape mortality once they exceed 50 mm, but for smaller corals mortality in brooders was double those of spawners (i.e. acroporids and massive corals). For corals on the reef flat, sensitivity analysis demonstrated that growth and mortality of larger juveniles (21–50 mm) highly influenced population dynamics; whereas the recruitment, growth and mortality of smaller corals (<20 mm) had the highest influence on reef slope population dynamics. Our results provide insight into the population dynamics and recovery trajectories in disparate reef habitats, and highlight the importance of acroporid recruitment in driving rapid increases in coral cover following large-scale perturbation in reef slope environments.     

Long-term persistence of low coral cover and abundance on a disturbed coral reef flat in the northern Red Sea

Levels of coral cover and abundance on a coral reef flat in Eilat (Israeli Red Sea) were estimated in 2001 by surveying nineteen 10-m transects, and compared to the levels reported in the same area between 1966 and 1973. Lower values compared to 1966 levels are evident, and there has been only a modest recovery following a catastrophic low tide that killed a large proportion of the corals in 1970. Percent cover of soft and stony corals (16.1%) was less than half of that reported for 1969 (35%), when a sharp decrease in coral abundance had already been observed. The total number of soft and stony coral colonies observed was 300, compared to 541 in 1966. In contrast to 1966, when half of the transects surveyed contained more than 30 coral colonies, no transects with this number of corals were observed. The cover of seven of the most common stony coral species was 841 cm, which is twice the coral cover of that in 1973, but only 22% of the 1969 level. Millepora dichotoma, an abundant species before 1970, has almost disappeared, and the soft coral Litophyton, abundant in 1972, was not observed. Anthropogenic nutrient enrichment is apparently among the causes for the lack of coral recovery in the studied reef flat. Reefs located further away from sources of pollution have recovered quickly after natural and anthropogenic disturbances and have retained their coral abundance and diversity.     

Predicting Coral Species Richness: The Effect of Input Variables,Diversity and Scale

Coral reefs are facing a biodiversity crisis due to increasing human impacts, consequently, one third of reef-building corals have an elevated risk of extinction. Logistic challenges prevent broad-scale species-level monitoring of hard corals; hence it has become critical that effective proxy indicators of species richness are established. This study tests how accurately three potential proxy indicators (generic richness on belt transects, generic richness on point-intercept transects and percent live hard coral cover on point-intercept transects) predict coral species richness at three different locations and two analytical scales. Generic richness (measured on a belt transect) was found to be the most effective predictor variable, with significant positive linear relationships across locations and scales. Percent live hard coral cover consistently performed poorly as an indicator of coral species richness. This study advances the practical framework for optimizing coral reef monitoring programs and empirically demonstrates that generic richness offers an effective way to predict coral species richness with a moderate level of precision. While the accuracy of species richness estimates will decrease in communities dominated by species-rich genera (e.g. Acropora), generic richness provides a useful measure of phylogenetic diversity and incorporating this metric into monitoring programs will increase the likelihood that changes in coral species diversity can be detected.     

The aftermath of coral bleaching on a Maldivian reef—a quantitative study

Since the bleaching event of 1998, the development of the reef flat and upper reef slope on a Maldivian reef (the Komandoo house reef; Komandoo Island, Lhaviyani atoll or Fadiffolu atoll) is under detailed observation. We quantitatively recorded specific losses, re-colonisation by coral larvae on transects on the reef flat and on dead Acropora tables at the reef slope and regeneration of partly damaged large Porites and Diploastrea—colonies over the period from 1999 to 2004. The detrimental effects on the reef structure by bioerosion and hydrodynamics, as well as the overall status of the reef community were qualitatively assessed. Recruitment soon after the bleaching was more pronounced than in the following years, Pavona varians being a main constituent. The temporal re-colonisation pattern points at an emergency spawning of local Scleractinia just prior to the bleaching, whereas a sharp decrease of young settlers in 2001 and 2002 confirms a reduction of fertile colonies. The dominant species in the coral community shifted from acroporids and pocilloporids to agariciids. The skeletal deposition of recovering Diploastrea heliopora was equivalent to that before the bleaching, but much less than that of neighbouring Porites lobata colonies. The slow and scattered formation of new reef substance, which would structurally strengthen the reef, is however outweighed by the collapse of dead protruding and spacious colonies (e.g., Acropora tables). Six years after the bleaching, the formerly three-dimensional structure of the reef flat and upper reef slope presents as a levelled field of rubble, only partly consolidated by incrusting corals. Considering the recurrence of bleaching events (1987, 1998) and the results of the present study, one may assume a cascading deterioration of the status of the reef for the future.     

Coral and sea urchin assemblage structure and interrelationships in Kenyan reef lagoons

Patterns of hard coral and sea urchin assemblage structure (species richness, diversity, and abundance) were studied in Kenyan coral reef lagoons which experienced different types of human resource use. Two protected reefs (Malindi and Watamu Marine National Parks) were protected from fishing and coral collection, but exposed to heavy tourist use. One reef (Mombasa MNP) received protection from fishermen for one year and was exploited for fish and corals prior to protection and was defined as a transitional reef. Three reefs (Vipingo, Kanamai, and Diani) were unprotected and experienced heavy fishing and some coral collection. Protected and unprotected reefs were distinct in terms of their assemblage structure with the transitional reef grouping with unprotected reefs based on relative and absolute abundance of coral genera. Protected reefs had slightly higher (p<0.01) coral cover (23.6 ± 8.3 % ± S.D.) than unprotected reefs (16.7 ± 8.5), but the transitional reef had the highest coral cover (30.8 ± 6.4) which increased by 250% since measured in 1987: largely attributable to a large increase inPorites nigrescens cover. Protected reefs had higher coral species richness and diversity and a greater relative abundance ofAcropora, Montipora andGalaxea than unprotected reefs. The transitional reef had high species richness, but lower diversity due to the high dominance ofPorites. Sea urchins showed the opposite pattern with highest diversity in most unprotected reefs. Coral cover, species richness, and diversity were negatively associated with sea urchin abundance, but the relative abundance ofPorites increased with sea urchin abundance to the point wherePorites composed >90% of the coral cover at sites with the highest sea urchin abundance. Effects of coral overcollection was only likely for the genusAcropora (staghorn corals). A combination of direct and indirect effects of human resource use may reduce diversity, species richness, and abundance of corals while increasing the absolute abundance of sea urchins and the relative cover ofPorites.     

Corals form characteristic associations with symbiotic nitrogen-fixing bacteria

The complex symbiotic relationship between corals and their dinoflagellate partner Symbiodinium is believed to be sustained through close associations with mutualistic bacterial communities, though little is known about coral associations with bacterial groups able to fix nitrogen (diazotrophs). In this study, we investigated the diversity of diazotrophic bacterial communities associated with three common coral species (Acropora millepora, Acropora muricata, and Pocillopora damicormis) from three midshelf locations of the Great Barrier Reef (GBR) by profiling the conserved subunit of the nifH gene, which encodes the dinitrogenase iron protein. Comparisons of diazotrophic community diversity among coral tissue and mucus microenvironments and the surrounding seawater revealed that corals harbor diverse nifH phylotypes that differ between tissue and mucus microhabitats. Coral mucus nifH sequences displayed high heterogeneity, and many bacterial groups overlapped with those found in seawater. Moreover, coral mucus diazotrophs were specific neither to coral species nor to reef location, reflecting the ephemeral nature of coral mucus. In contrast, the dominant diazotrophic bacteria in tissue samples differed among coral species, with differences remaining consistent at all three reefs, indicating that coral-diazotroph associations are species specific. Notably, dominant diazotrophs for all coral species were closely related to the bacterial group rhizobia, which represented 71% of the total sequences retrieved from tissue samples. The species specificity of coral-diazotroph associations further supports the coral holobiont model that bacterial groups associated with corals are conserved. Our results suggest that, as in terrestrial plants, rhizobia have developed a mutualistic relationship with corals and may contribute fixed nitrogen to Symbiodinium.     

Effects of herbivory,nutrients, and reef protection on algal proliferation and coral growth on a tropical reef

Maintaining coral reef resilience against increasing anthropogenic disturbance is critical for effective reef management. Resilience is partially determined by how processes, such as herbivory and nutrient supply, affect coral recovery versus macroalgal proliferation following disturbances. However, the relative effects of herbivory versus nutrient enrichment on algal proliferation remain debated. Here, we manipulated herbivory and nutrients on a coral-dominated reef protected from fishing, and on an adjacent macroalgal-dominated reef subject to fishing and riverine discharge, over 152 days. On both reefs, herbivore exclusion increased total and upright macroalgal cover by 9-46 times, upright macroalgal biomass by 23-84 times, and cyanobacteria cover by 0-27 times, but decreased cover of encrusting coralline algae by 46-100% and short turf algae by 14-39%. In contrast, nutrient enrichment had no effect on algal proliferation, but suppressed cover of total macroalgae (by 33-42%) and cyanobacteria (by 71% on the protected reef) when herbivores were excluded. Herbivore exclusion, but not nutrient enrichment, also increased sediment accumulation, suggesting a strong link between herbivory, macroalgal growth, and sediment retention. Growth rates of the corals Porites cylindrica and Acropora millepora were 30-35% greater on the protected versus fished reef, but nutrient and herbivore manipulations within a site did not affect coral growth. Cumulatively, these data suggest that herbivory rather than eutrophication plays the dominant role in mediating macroalgal proliferation, that macroalgae trap sediments that may further suppress herbivory and enhance macroalgal dominance, and that corals are relatively resistant to damage from some macroalgae but are significantly impacted by ambient reef condition.     

The effect of Hurricane Allen on the Bellairs fringing reef,Barbados

On August 4, 1980 Hurricane Allen damaged the northern fringing reef located just offshore from the Bellairs Research Institute of McGill University on the west coast of Barbados. During the summer and one winter month of 1981 a resurvey of the reef was done and the results were compared with a similar survey made in 1974. On a reefal scale the changes in the proportion of substrates before and after Hurricane Allen were statistically significant for all substrates and species with the exception of Millepora spp. Among the corals, Porites porites has been most affected by the catastrophe: its coverage was reduced by 96%. The other corals (Siderastrea sidera, Porites astreoides, Montastrea annularis, and Agaricia agaricites) were reduced by 75 to 25%. Onshore transport is suggested by the high abundance of Acropora cervicornis (20%) and Madracis mirabilis (30%) in the rubble on the fringing reef (the former only grows seaward of the reef). Offshore transport is suggested by the relatively poor representation of Porites porites (32%) in the rubble. Shannon-Weaver diversity indices of the corals dropped from 1.61 to 1.26. The changes in diversity are best explained by the intermediate disturbance hypothesis.     

Coral associations of the Pleistocene Ironshore Formation,Grand Cayman

The 125-ka sea level, which was approximately 6 m above present-day sea level, led to the partial flooding of many Caribbean islands. On Grand. Cayman, this event led to the formation of the large Ironshore Lagoon that covered most of the western half of the island and numerous, small embayments along the south, east, and north coasts. At that time, at least 33 coral species grew in waters around Grand Cayman. This fauna, like the modern coral fauna of Grand Cayman, was dominated byMontastrea annularis, Porites porites, Acropora polmata, andA. cervicornis. Scolymia cubensis andMycetophyllia ferox, not previously identified from the Late Pleistocene, are found in the Pleistocene patch reefs.Madracis mirabilis, Colpophyllia breviserialis, Agaricia tenuifolia, A. lamarcki, A. undata, Millepora spp., Mycetophyllia reesi, M. aliciae, andM. danaana, found on modern reefs, have not been identified from the Late Pleistocene reefs. Conversely,Pocillopora sp. cf.P. palmata, which is found in Late Pleistocene reefs, is absent on the modern reefs around Grand Cayman. The corals in the Ironshore Formation of Grand Cayman have been divided into 10 associations according to their dominant species, overall composition, and faunal diversity. Many of these associations are similar to the modern associations around Grand Cayman. Each of the Pleistocene coral associations, which can be accurately located on the known Late Pleistocene paleogeography of Grand Cayman, developed in distinct environmental settings. Overall trends identified in the modern settings are also apparent in the Late Pleistocene faunas. Thus, the diversity of the coral faunas increased from the interior of the Ironshore Lagoon to the reef crest. Similarly, the coral diversity in the Pleistocene patch reefs was related to the size of the reefs and their position relative to breaks in the barrier reef. The barrier reef included corals that are incapable of sediment rejection; whereas the patch reefs lacked such corals.     

Identity and diversity of coral endosymbionts (zooxanthellae) from three Palauan reefs with contrasting bleaching, temperature and shading histories

The potential of corals to associate with more temperature-tolerant strains of algae (zooxanthellae, Symbiodinium) can have important implications for the future of coral reefs in an era of global climate change. In this study, the genetic identity and diversity of zooxanthellae was investigated at three reefs with contrasting histories of bleaching mortality, water temperature and shading, in the Republic of Palau (Micronesia). Single-stranded conformation polymorphism and sequence analysis of the ribosomal DNA internal transcribed spacer (ITS)1 region was used for genotyping. A chronically warm but partly shaded coral reef in a marine lake that is hydrographically well connected to the surrounding waters harboured only two single-stranded conformation polymorphism profiles (i.e. zooxanthella communities). It consisted only of Symbiodinium D in all 13 nonporitid species and two Porites species investigated, with the remaining five Porites harbouring C*. Despite the high temperature in this lake (> 0.5 degrees above ambient), this reef did not suffer coral mortality during the (1998) bleaching event, however, no bleaching-sensitive coral families and genera occur in the coral community. This setting contrasts strongly with two other reefs with generally lower temperatures, in which 10 and 12 zooxanthella communities with moderate to low proportions of clade D zooxanthellae were found. The data indicate that whole coral assemblages, when growing in elevated seawater temperatures and at reduced irradiance, can be composed of colonies associated with the more thermo-tolerant clade D zooxanthellae. Future increases in seawater temperature might, therefore, result in an increasing prevalence of Symbiodinium phylotype D in scleractinian corals, possibly associated with a loss of diversity in both zooxanthellae and corals.     

Effects of disturbance on coral communities: bleaching in Moorea,French Polynesia

This study examines patterns of susceptibility and short-term recovery of corals from bleaching. A mass coral bleaching event began in March, 1991 on reefs in Moorea, French Polynesia and affected corals on the shallow barrier reef and to >20 m depth on the outer forereef slope. There were significant differences in the effect of the bleaching among common coral genera, with Acropora, Montastrea, Montipora, and Pocillopora more affected than Porites, Pavona, leptastrea or Millepora. Individual colonies of the common species of Acropora and Pocillopora were marked and their fate assessed on a subsequent survey in August, 1991 to determine rates of recovery and mortality. Ninety-six percent of Acropora spp. showed some degree of bleaching compared to 76% of Pocillopora spp. From March to August mortality of bleached colonies of Pocillopora was 17%, 38% recovered completely, and many suffered some partial mortality of the tissue. In contrast, 63% of the Acropora spp. died, and about 10% recovered completely. Generally, those colonies with less than 50% of the colony area affected by the bleaching recovered at a higher rate than did those with more severe bleaching. Changes in community composition four months after the event began included a significant decrease only in crustose algae and an increase in cover of filamentous algae, much of which occupied plate-like and branching corals that had died in the bleaching event. Total coral cover and cover of susceptible coral genera had declined, but not significantly, after the event.     

Comparison of coral diversity between big and small atolls: a case study of Yongle atoll and Lingyang reef,Xisha Islands,central of South China Sea

The South China Sea (SCS) includes large areas of extensive coral reef development but its reefs are still poorly known. Yongle atoll is the biggest typical atoll in the Xisha Islands, central of SCS. Lingyang Reef is an isolated small atoll within the whole big Yongle atoll. A total of 144 and 119 coral species were recorded at big Yongle atoll and small Lingyang Reef, respectively. The real coral richness might be higher because species accumulation curve did not saturate. The coral diversity pattern was similar between big Yongle atoll and small Lingyang Reef. Coral communities fell into three clusters, consistent with their habitats on reef slope, reef flat and lagoon slope. The highest coral diversity was observed on reef slopes and the lowest coral diversity was found on lagoon slope. Genera richness was a better proxy for representing coral species diversity on both the big and small atoll but percent live coral cover was not a robust proxy on the small atoll, which only explained 24% of species diversity. This study demonstrated high coral diversity with consistent pattern along habitat types, as has been shown from many other reefs. While far from exhaustive, the study allows first glimpses on how much biodiversity is contained on SCS coral reefs, and hopes to give an impetus to their conservation. The study also suggests that simplified surveys at a small scale and the use of genera richness as an effective proxy for overall diversity can indeed provide important information to rapidly monitor and evaluate the coral diversity in remote locations.     

Reef community structure at Falcón, Venezuela, before and after a mass mortality

Morrocoy National Park used to be considered the most important continental coral reef of Venezuela. However, in January of 1996, there was a massive mortality of the benthic organisms for unknown reasons. The coral reef community was monitored since 1995, the year before the event, and yearly after that, until June 1999, by sampling linear transects and quadrats. A total of 26 hard corals were recorded in the study site (Playa Mero) in 1995 (36.56% cover), which already had some deterioration because 90.86% of the living coral cover was represented basically by four species, M. annularis with 51.36%, Colpophyllia natans with 18.22%, Agaricia agaricites with 11.58% and Porites porites with 9.70%. Three months after the event, living coral cover was only 4.84% and algae, particularly Dyctiota spp. covered most of the surface (81.89%). Benthic organisms suffered massive mortality over the whole depth gradient and in most park reefs. Even after three years the reef community shows highly perturbed conditions, with 85% of the total cover represented by the categories: dead coral, dead coral overgrowth by algae and sand. From the initial coral richness of the area (26 species) only nine species were observed although in very low cover (<1%), except for M. annularis and M. franksi, which presented lightly higher percentages.