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Surviving Coral Bleaching Events: Porites Growth Anomalies on the Great Barrier Reef  [PDF]
Neal E. Cantin, Janice M. Lough
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088720
Abstract: Mass coral bleaching affected large parts of the Great Barrier Reef (GBR) in 1998 and 2002. In this study, we assessed if signatures of these major thermal stress events were recorded in the growth characteristics of massive Porites colonies. In 2005 a suite of short (<50 cm) cores were collected from apparently healthy, surviving Porites colonies, from reefs in the central GBR (18–19°S) that have documented observations of widespread bleaching. Sites included inshore (Nelly Bay, Pandora Reef), annually affected by freshwater flood events, midshelf (Rib Reef), only occasionally affected by freshwater floods and offshore (Myrmidon Reef) locations primarily exposed to open ocean conditions. Annual growth characteristics (extension, density and calcification) were measured in 144 cores from 79 coral colonies and analysed over the common 24-year period, 1980–2003. Visual examination of the annual density bands revealed growth hiatuses associated with the bleaching years in the form of abrupt decreases in annual linear extension rates, high density stress bands and partial mortality. The 1998 mass-bleaching event reduced Porites calcification by 13 and 18% on the two inshore locations for 4 years, followed by recovery to baseline calcification rates in 2002. Evidence of partial mortality was apparent in 10% of the offshore colonies in 2002; however no significant effects of the bleaching events were evident in the calcification rates at the mid shelf and offshore sites. These results highlight the spatial variation of mass bleaching events and that all reef locations within the GBR were not equally stressed by the 1998 and 2002 mass bleaching events, as some models tend to suggest, which enabled recovery of calcification on the GBR within 4 years. The dynamics in annual calcification rates and recovery displayed here should be used to improve model outputs that project how coral calcification will respond to ongoing warming of the tropical oceans.
Assessment of Present Status and Future Needs of Four Coral Reef Sites Along the Gulf of Aqaba, Egypt
Mohammed Shokry Ahmed Ammar
The Open Environmental Pollution & Toxicology Journal , 2009, DOI: 10.2174/1876397900901010034]
Abstract: The present status and future needs of four coral reef sites (Taba, Nuweiba , Dahab and Sharm El-Sheikh) along the Gulf of Aqaba, Egypt were evaluated. A total of 60 quadrats, distributed at different depths or different patches were surveyed at each site during the year 2007. Three mooring buoys were reported only in Ras Umm Seid but nothing was found in other sites, however excessive boating and diving pressure were recorded only in Ras Umm Seid. Highest amount of garbage was recorded in Nuweiba, patrolling efficiency was best in Taba but no patrolling activities were recorded in other sites. Ras Umm Seid (Sharm El-Sheikh) had the highest amount of dead corals (13%) due to increased boating and diving pressure compared to other sites, however Dahab had the lowest amount of dead corals (4%) due to the rough conditions (strong wind and waves) causing difficulties in accessing that site. Nuweiba and Taba had high percent cover of sands (10% and 11%, respectively) playing a key role in the considerable amount of dead corals in both sites. Lowest % new coral recruits in Taba (0.5%) was associated with the soft sandy bottom, the opposite was true in Sharm El Sheikh due to the rocky bottom. Future needs of the studied sites include decreasing the number of divers to the diver carrying capacity (DCC), repair of existing buoys and incorporation of 5 more buoys in Ras Umm Seid. Other sites have no future needs in these regards as they are far beyond the DCC. Nuweiba needs first of all to be cleaned, then being protected for giving the chance of recovery. Except for Taba which has efficient patrolling, the other 3 sites need efficient terrestrial and marine patrolling as well as enforcement of EEAA regulations. However reef access points which were absent in all sites need to be established to minimize reef damage on accessing deeper water. Also, the environmental awareness field signs which were absent in all sites need to be established and managed. Taba is recommended as a protected area as it has the food for threatened species beside being useful as a nesting site. Ras Umm Seid is recommended to have a established artificial reef to draw the attention of divers and snorklers from the natural reefs and prepare artificial shelters for fishes thus promoting the fish resources.
Reconstructing skeletal fiber arrangement and growth mode in the coral Porites lutea (Cnidaria, Scleractinia): a confocal Raman microscopy study
M. Wall,G. Nehrke
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Confocal Raman microscopy (CRM) mapping was used to investigate the microstructural arrangement and organic matrix distribution within the skeleton of the coral Porites lutea. Relative changes in the crystallographic orientation of crystals within the fibrous fan-system could be mapped, without the need to prepare thin sections, as required if this information is obtained by polarized light microscopy. Simultaneously, incremental growth lines can be visualized without the necessity of etching and hence alteration of sample surface. Using these methods two types of growth lines could be identified: one corresponds to the well-known incremental growth layers, whereas the second type of growth lines resemble denticle finger-like structures (most likely traces of former spines or skeletal surfaces). We hypothesize that these lines represent the outer skeletal surface before another growth cycle of elongation, infilling and thickening of skeletal areas continues. We show that CRM mapping with high spatial resolution can significantly improve our understanding of the micro-structural arrangement and growth patterns in coral skeletons.
Reconstructing skeletal fiber arrangement and growth mode in the coral Porites lutea (Cnidaria, Scleractinia): a confocal Raman microscopy study
M. Wall,G. Nehrke
Biogeosciences (BG) & Discussions (BGD) , 2012, DOI: 10.5194/bg-9-4885-2012
Abstract: Confocal Raman microscopy (CRM) mapping was used to investigate the microstructural arrangement and organic matrix distribution within the skeleton of the coral Porites lutea. Relative changes in the crystallographic orientation of crystals within the fibrous fan-system could be mapped, without the need to prepare thin sections, as required if this information is obtained by polarized light microscopy. Simultaneously, incremental growth lines can be visualized without the necessity of etching and hence alteration of sample surface. Using these methods two types of growth lines could be identified: one corresponds to the well-known incremental growth layers, whereas the second type of growth lines resemble denticle finger-like structures (most likely traces of former spines or skeletal surfaces). We hypothesize that these lines represent the outer skeletal surface before another growth cycle of elongation, infilling and thickening of skeletal areas continues. We show that CRM mapping with high spatial resolution can significantly improve our understanding of the micro-structural arrangement and growth patterns in coral skeletons.
Coral Skeletons Provide Historical Evidence of Phosphorus Runoff on the Great Barrier Reef  [PDF]
Jennie Mallela, Stephen E. Lewis, Barry Croke
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075663
Abstract: Recently, the inshore reefs of the Great Barrier Reef have declined rapidly because of deteriorating water quality. Increased catchment runoff is one potential culprit. The impacts of land-use on coral growth and reef health however are largely circumstantial due to limited long-term data on water quality and reef health. Here we use a 60 year coral core record to show that phosphorus contained in the skeletons (P/Ca) of long-lived, near-shore Porites corals on the Great Barrier Reef correlates with annual records of fertiliser application and particulate phosphorus loads in the adjacent catchment. Skeletal P/Ca also correlates with Ba/Ca, a proxy for fluvial sediment loading, again linking near-shore phosphorus records with river runoff. Coral core records suggest that phosphorus levels increased 8 fold between 1949 and 2008 with the greatest levels coinciding with periods of high fertiliser-phosphorus use. Periods of high P/Ca correspond with intense agricultural activity and increased fertiliser application in the river catchment following agricultural expansion and replanting after cyclone damage. Our results demonstrate how coral P/Ca records can be used to assess terrestrial nutrient loading of vulnerable near-shore reefs.
Declining Coral Skeletal Extension for Forereef Colonies of Siderastrea siderea on the Mesoamerican Barrier Reef System, Southern Belize  [PDF]
Karl D. Castillo,Justin B. Ries,Jack M. Weiss
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014615
Abstract: Natural and anthropogenic stressors are predicted to have increasingly negative impacts on coral reefs. Understanding how these environmental stressors have impacted coral skeletal growth should improve our ability to predict how they may affect coral reefs in the future. We investigated century-scale variations in skeletal extension for the slow-growing massive scleractinian coral Siderastrea siderea inhabiting the forereef, backreef, and nearshore reefs of the Mesoamerican Barrier Reef System (MBRS) in the western Caribbean Sea.
Macroalgae Decrease Growth and Alter Microbial Community Structure of the Reef-Building Coral, Porites astreoides  [PDF]
Rebecca Vega Thurber, Deron E. Burkepile, Adrienne M. S. Correa, Andrew R. Thurber, Andrew A. Shantz, Rory Welsh, Catharine Pritchard, Stephanie Rosales
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044246
Abstract: With the continued and unprecedented decline of coral reefs worldwide, evaluating the factors that contribute to coral demise is of critical importance. As coral cover declines, macroalgae are becoming more common on tropical reefs. Interactions between these macroalgae and corals may alter the coral microbiome, which is thought to play an important role in colony health and survival. Together, such changes in benthic macroalgae and in the coral microbiome may result in a feedback mechanism that contributes to additional coral cover loss. To determine if macroalgae alter the coral microbiome, we conducted a field-based experiment in which the coral Porites astreoides was placed in competition with five species of macroalgae. Macroalgal contact increased variance in the coral-associated microbial community, and two algal species significantly altered microbial community composition. All macroalgae caused the disappearance of a γ-proteobacterium previously hypothesized to be an important mutualist of P. astreoides. Macroalgal contact also triggered: 1) increases or 2) decreases in microbial taxa already present in corals, 3) establishment of new taxa to the coral microbiome, and 4) vectoring and growth of microbial taxa from the macroalgae to the coral. Furthermore, macroalgal competition decreased coral growth rates by an average of 36.8%. Overall, this study found that competition between corals and certain species of macroalgae leads to an altered coral microbiome, providing a potential mechanism by which macroalgae-coral interactions reduce coral health and lead to coral loss on impacted reefs.
Temporal variations in coral reef health at a coastal industrial site on the Gulf of Aqaba, Red Sea
Mohammad K. Al-Zibdah,Said A. Damhoureyeh,Mohammad I. Badran
Oceanologia , 2007,
Abstract: A detailed ecological study was conducted for three years (2001-03) on a 5 km stretch of well-developed coral reeffacing an industrial site in the southernmost section of the Jordanian coast of the Gulf of Aqaba, Red Sea. The degreeof modification associated with the prevailing ecological factors was assessed with respect to species diversity and abundanceof the major groups of the macrobenthic community: corals, bivalves, hydrozoans, echinoderms, sponges and macroalgae. Three locations of two depths each - 6 and 12 m - were selected and surveyed using the visual census point-intercept method. The actual area of the survey covered about 2250 m2. Macrobenthic communities occurring close to the industrial jetty were characterized by low diversity and the obvious dominance of soft coral (16-30% cover). In the deep transects (12 m) hard coral cover was higher than that in the shallow transects (30-55%). Correlation analyses indicated that species richness increased with increasing distance from the industrial jetty. Species richness of other macrobenthos was also higher as depth increased. The results revealed that the distribution and abundance of coral, echinoderms, hydrozoans and macroalgae were correlated with the relative importance of bottom modification within the various locations in the entire study area. However, no distinct influence of location or depth on the identities of most macrobenthic species was indicated.
Anthropogenic stressors and eutrophication processes as recorded by stable isotopes compositions in coral skeletons  [PDF]
O. Levy,M. Rosenfeld,Y. Loya,R. Yam
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-7657-2010
Abstract: The northern Gulf of Aqaba, in the northeastern branch of the Red Sea, is a clear example of humans effecting on the health of fringing reefs. Our results demonstrate the effect of an anthropogenic stressor on the carbon and oxygen stable isotopes compositions, namely net pen fish farming with annual fish production of 2.4×106 kg yr 1. We sampled and studied long coral cores from stressed, remote and intermediate localities and short- term transplanted Porites sp. colonies from the west side of the Gulf of Aqaba to a remote and a polluted sites, respectively. The data shows that mariculture and other human related stressors did not influence the oxygen isotopic signature over a period of two decades. However, the carbon fractionation changed along a geographical gradient and depended on proximity to the source of contamination. We suggest that δ13C of coral skeleton is a promising proxy for identifying long term processes of coral growth under high nutrient loads and potential disturbances to the coral reef ecology.
Spatial pattern of coral diversity in Luhuitou fringing reef, Sanya, China

Zhao Meixi,Yu Kefu,Zhang Qiaomin,Shi Qi,

生态学报 , 2008,
Abstract: 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.
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