Coral Reef Areas Research Articles

Abundance and local-scale processes contribute to multi-phyla gradients in global marine diversity.

Among the most enduring ecological challenges is an integrated theory explaining the latitudinal biodiversity gradient, including discrepancies observed at different spatial scales. Analysis of Reef Life Survey data for 4127 marine species at 2406 coral and rocky sites worldwide confirms that the total ecoregion richness peaks in low latitudes, near +15°N and -15°S. However, although richness at survey sites is maximal near the equator for vertebrates, it peaks at high latitudes for large mobile invertebrates. Site richness for different groups is dependent on abundance, which is in turn correlated with temperature for fishes and nutrients for macroinvertebrates. We suggest that temperature-mediated fish predation and herbivory have constrained mobile macroinvertebrate diversity at the site scale across the tropics. Conversely, at the ecoregion scale, richness responds positively to coral reef area, highlighting potentially huge global biodiversity losses with coral decline. Improved conservation outcomes require management frameworks, informed by hierarchical monitoring, that cover differing site- and regional-scale processes across diverse taxa, including attention to invertebrate species, which appear disproportionately threatened by warming seas.

Variación espacial en número de especies, abundancia y diversidad de peces en las Bahías de Huatulco, Oaxaca, México

Coral reef fish may adapt to their habitat characteristics, and the particular system intrinsic factors, may cause different fish compositions and structures. The present study aimed to determine the variation in number of species, abundance and diversity of fish communities in Huatulco bays of San Agustin, Riscalillo, Chachacual, Cacaluta, Maguey, Organo, Violín and La Entrega, from Oaxaca, Mexico. Fish communities were characterized between January 2009 and December 2010, with the use of visual census techniques. A total of 351 transects (10 x 2.5 m) were made, and for each one we analyzed the ichthyofauna species number, abundance and diversity. The analysis showed that for all variables, the highest values corresponded to Maguey, La Entrega, Órgano and Violín bays, while the lowest values corresponded to the San Agustín, Riscalillo, Chachacual and Cacaluta bays. The study identified significant differences in diversity (Kruskal-Wallis=18.71, P= 0.0091), and in the composition and structure of fish communities in the bays (ANOSIM= 0.278, P= 0.001). We observed a relationship between the number of fish species and number of coral species (Spearman=0.591, P< 0.05), while no relationship was found between the coral reef area and the number of fish species or their abundances. The number of coral species and the patchy arrangement of the coral cover created habitats that are structurally more complex, which affects the number of fish species. In areas with developed tourist infrastructure, recreational aquatic activities were found to affect the ichthyofauna behavior, abundance and diversity. The new information of this study may contribute to create and improve management, conservation and protection strategies for this important area as a whole interconnected complex.

Wind forcing of sea level variability in a tropical coral reef area in the western Gulf of Mexico

Sea level, water temperature, and wind stress data were obtained from the Western Gulf of Mexico to elucidate the relationship between sea level changes and meteorological variables in a tropical coral reef system. Sea level and water temperature data were measured with a series of acoustic Doppler current profilers anchored at a depth of approximately 13 m in the Veracruz Reef System. The barometric and wind stress data were obtained from an automatic coastal weather station. Principal Component Analysis was applied to the series to determine the relative influence of the different meteorological variables on sea level. The seasonal variability of sea level is evident in the year-long data (September 2008 to April 2010) with a thermal expansion during the summer. Barometric pressure was found to be the second strongest forcing mechanism of sea level variability and not the first one. Opposite to what would be expected in protected coastal areas where the wind forcing mechanism on sea level may not be as important. The local winds were the main forcing mechanism of the sea level variability from March to September, while the meridional winds were more important than local winds from October to February.

Island-enhanced cooling mechanism in typhoon events revealed by field observations and numerical simulations for a coral reef area, Sekisei Lagoon, Japan

While widely known for their destructive power, typhoon events can also bring benefit to coral reef ecosystems through typhoon-induced cooling which can mitigate against thermally stressful conditions causing coral bleaching. Sensor deployments in Sekisei Lagoon, Japan’s largest coral reef area, during the summer months of 2013, 2014, and 2015 were able to capture local hydrodynamic features of numerous typhoon passages. In particular, typhoons 2015-13 and 2015-15 featured steep drops in near-bottom temperature of 5 °C or more in the north and south sides of Sekisei Lagoon, respectively, indicating local cooling patterns which appeared to depend on the track and intensity of the passing typhoon. This was further investigated using Regional Ocean Modeling System (ROMS) numerical simulations conducted for the summer of 2015. The modeling results showed a cooling trend to the north of the Yaeyama Islands during the passage of typhoon 2015-13, and a cooling trend that moved clockwise from north to south of the islands during the passage of typhoon 2015-15. These local cooling events may have been initiated by the Yaeyama Islands acting as an obstacle to a strong typhoon-generated flow which was modulated and led to prominent cooling of waters on the leeward sides. These lower temperature waters from offshore may then be transported to the shallower inner parts of the lagoon area, which may partly be due to density-driven currents generated by the offshore-inner area temperature difference.

Nutrient Distribution in Coral Reef Degraded Areas within Sanya Bay, South China Sea

ABSTRACT Guo, J.; Yu, K.; Wang, Y.; Xu, D.; Huang, X.; Zhao, M.; Yang, H., and Zhang, R., 2017. Nutrient distribution in Coral Reef degraded areas within Sanya Bay, South China Sea. An investigation was conducted in August 2014 to explore the spatial distribution of dissolved inorganic nitrogen (DIN) and phosphate ( ) in overlying water, pore water, and surface sediment from Sanya Bay and living coral cover on Luhuitou fringing reef. Generally, nutrient contents gradually decreased from the estuary to the central bay, which confirmed that terrigenous inputs from Sanya River and Sanya Harbor were the primary nutrient sources. The results of K-means cluster analysis suggested the Luhuitou fringing reef is in danger of being affected by the pollution source. The results of nutrient diffusive fluxes at the sediment-seawater interface indicated diffusion from pore water to overlying water. Compared with other coral reef areas around the world, nutrient levels in Luhuitou fringing reef were at the medium level....

Planning for the future: Incorporating global and local data to prioritize coral reef conservation

Abstract It is necessary, yet challenging, to manage coral reefs to simultaneously address a suite of global and local stressors that act over the short and long term. Therefore, managers need practical guidance on prioritizing the locations and types of conservation that most efficiently address their goals using limited resources. This study is one of the first examples of a vulnerability assessment for coral reefs that uses downscaled global climate change projections and local anthropogenic stress data to prioritize coral reef locations for conservation investment. Vulnerability was separated into manageable and unmanageable components (bleaching likelihood and local anthropogenic stressors, respectively), and the highest priority was given to places with low levels of unmanageable threats and high levels of manageable threats. Following prioritization, resilience characteristics were derived from standard reef monitoring data and used to identify the specific conservation strategies most likely to succeed given local ecological conditions and threats. Using Indonesian coral reefs as a case study, 9.1% of total coral reef area was identified as of high conservation priority, including parts of Raja Ampat, Sulawesi, and Sumatra that are not currently included in marine protected areas (MPAs). Existing MPAs tend to be located in areas less threatened by local‐scale anthropogenic activities, which has implications for both the implementation costs and the likely impact of conservation investment. This approach employs common and publicly available data and can therefore be replicated wherever managers face the familiar challenge of allocating limited conservation resources in the face of rapid global change and uncertainty.

Status of Diadema antillarum populations in Grand Anse Bay, Grenada, 30 years after mass mortality

Since the mass mortality of Diadema antillarum Philippi, 1845 populations in 1983–1984, recovery has been slow and D. antillarum remain scarce at many localities across the Caribbean Sea. Yet, in 2014 we observed high densities of D. antillarum over relatively large areas of shallow nearshore coral reefs in Grand Anse Bay, Grenada. The present study sought to assess D. antillarum populations at two high-density sites in Grand Anse Bay during 2014–2015 to determine the status of D. antillarum populations on those reefs. Mean D. antillarum densities at the two sites surveyed in Grenada were relatively high [5.9 (SE 0.57) and 12.5 (SE 0.74) individuals m–2] compared with the average density (4.5 individuals m–2) of D. antillarum from a previous study in Grand Anse Bay. The majority of individuals identified at the two sites were small (9–39 mm) to medium size (40–59 mm) sea urchins. Mean density of juvenile D. antillarum (<20 mm) at site 1 was significantly greater during a nighttime survey compared with a daytime survey, suggesting that daytime surveys may have been underestimating abundance of juvenile D. antillarum on those reefs. The high density of small to medium size sea urchins, as well as the presence of several juveniles observed at night, suggests that the high D. antillarum densities found at these two sites in Grenada were unlikely to be limited by fertilization success, larval production, and/or larval survivorship.

The social feather duster worm Bispira brunnea (Polychaeta: Sabellidae): aggregations, morphology and reproduction

ABSTRACTThe fan worm Bispira brunnea is one of the most attractive sabellid polychaetes from Caribbean coral reef areas and it is exploited for ornamental purposes. An understanding of the structure of its aggregations, morphology and reproductive biology will provide information required to facilitate artificial propagation of this species. Ten aggregations were collected in October 2013, February and March 2014 in the Majahual reef lagoon, Mexican Caribbean. Whole aggregations were examined under light microscopy and scanning electron microscopy and the histology of oogenesis was determined. Aggregations were composed of 24–56 individuals and included juveniles and adults. The adults (5–20 mm) did not display any noticeable form of sexual dimorphism. In B. brunnea both sexual (hermaphroditism or gonochorism) and asexual reproduction occurred at the same time within the population: 92.71% reproduced sexually and 52% by architomy. The buds produced by architomy were inside the parental tube, at three regenerative stages. The sex ratio was 36.75% males, 33.11% females, 22.84% hermaphrodites and 7.28% unknown (gametes not seen). Gametes were distributed in the last thoracic segments and throughout the abdomen. Oogenesis was extra-ovarian, development followed four discrete stages and the oocytes were small and asynchronous (60.97 μm in diameter). Sperm morphology was adapted to external fertilization in the water column. Sequential (protandrous) hermaphroditism is suggested to occur in B. brunnea. The pyramidellid ectosymbiont mollusc Odostomia (Eulimastoma) caniculatum is recorded here for the first time as being associated with a sabellid worm.

Shelter use by large reef fishes: long-term occupancy and the impacts of disturbance

Large fishes often shelter beneath structures on coral reefs. While avoidance of UV radiation has been proposed as the main driver of this behaviour, sheltering behaviour has only been studied during the day and over short timeframes. Here we applied passive acoustic telemetry techniques to continuously monitor shelter usage patterns by large reef fishes over a period of 7 months. For three sweetlip species (Haemulidae), one snapper species (Lutjanidae) and one surgeonfish species (Acanthuridae), diurnal shelter use was remarkably consistent, with occupation of shelters throughout the day, and under all weather conditions, suggesting that factors other than UV avoidance may be important in driving shelter use. Large-scale observations revealed that all fish species appeared to undertake long-distance migrations (>1 km) away from their shelter sites each night. With the exception of the surgeonfish Acanthurus dussumieri, all fishes returned to the same areas to shelter for the entire study period. Individuals of A. dussumieri, however, failed to return on the night of a severe tropical cyclone. They never reappeared at the shelter sites. The disappearance of this species suggests that A. dussumieri probably forage at night in a different location to the carnivorous haemulids and lutjanids. Overall, this study highlights the long-term importance of shelter structures for fishes that may range over large areas of coral reefs.

GENETIC VARIATION AND POPULATION STRUCTURE IN THE HUMPBACK GROUPER, Cromileptes altivelis, TROUGHOUT ITS RANGE IN INDONESIAN WATERS

Starch gel electrophoresis was used to assess the level and distribution ofgenetic variation in humpback grouper, Cromileptes altiuelis sampled from 4 different areas of coral reefs in Raas and Kangean located in Madura as well as Sangeang and Bungin located in Sumbawa regions, between December 1997 and March 1998.

Assessment of Machine Learning Approaches for Bathymetry Mapping in Shallow Water Environments using Multispectral Satellite Images

This paper evaluates the performance of two proposed empirical approaches—random forest (RF) and multi-adaptive regression spline (MARS)—for bathymetry calculations in three diverse areas: the Alexandria harbor shallow coastal area, Egypt, as an example of a low-turbidity, silt-sand bottom water area with depths ranging from 4 m to 10.5 m; the Lake Nubia entrance zone, Sudan, which is considered a high-turbidity, unstable, clay bottom area with a depth of 6 m; and Shiraho, Ishigaki Island, Japan, a coral reef area with a depth of 14 m. Data from Landsat 8 and Spot 6 satellite images were used to evaluate the performance of the proposed models. The bathymetry results of the proposed models were compared with the corresponding results yielded from two conventional empirical methods: the neural network (NN) model and the Lyzenga generalized linear model (GLM). When compared with echo sounder data, the RF and MARS results outperformed Lyzenga GLM results. Moreover, the RF method produced more accurate results with average 0.25 m RMSE improvements range than the NN model. The RF algorithm produced the most accurate results proved to be a preferable algorithm for bathymetry mapping in the shallow water context.

Reef fish diversity of bottom set gillnet landings at Pamban, Tamil Nadu, India

The coral reef areas of Gulf of Mannar support a rich fauna of fishes and bottom set gill net is one of the important gears employed in this area. Reef fishes landed at Pamban fish landing centre by bottom-set gillnets operated in Gulf of Mannar, for a period of three years from January, 2009 to December, 2011 were studied based on fortnightly sampling. A total of 69 species belonging to 29 families were recorded during the study and as per IUCN, two species, Himantura uarnak and Rhinoptera javanica are included under the Vulnerable category. The landings amounted to 1761 tonnes during the period with a maximum contribution of 44% during 2011 and it was the minimum during 2010 with a share of 27%. Species-wise landings indicated the dominance of Lethrinus nebulosus (11.5%) followed by Neotrygon kuhlii (10.6%). The richness and diversity indices showed a gradual increase from 2009 to 2011 and all the year wise points in the funnel plot for variation in taxonomic distinctness (λ+) are within the expected limit. The qualitative and quantitative abundance along with different diversity measures are presented and discussed in this paper. The results of the present investigation suggest that the bottom set gill net fishery is in a healthy condition with respect to Pamban fish landing centre.

Kajian Metode Klasifikasi Citra Landsat-8 untuk Pemetaan Habitat Bentik di Kepulauan Padaido, Papua

&lt;strong&gt;Assessment of Landsat-8 Classification Method for Benthic Habitat Mapping in Padaido Islands, Papua.&lt;/strong&gt; Indonesia is the biggest archipelagic country in the world with an area of coral reefs of 39,583 km.This area has to be managed effectively and efficiently utilizing satellite remote sensing technique capable of mapping of benthic habitat coverage, such as coral reefs, seagrasses, macroalgae, and bare substrates. The technique is supported by the availability of Landsat-8 OLI satellite images that have been recording the regions of Indonesia continuously every 16 days. This research was carried out in June 2015 in parts of Padaido Islands, Papua. This area was selected due to high coral reef damages. This study utilized Landsat-8 OLI to compare two classification methods, namely pixel based and object based methods using ‘maximum 2 likelihood’ (ML) and ‘example based feature extraction’ classifications, respectively, after water column correction (Lyzenga method). The results showed that both methods produced benthic habitat maps with 7 class covers. The pixel-based classification resulted in a better overall accuracy (47.57%) in the mapping of benthic habitats than object-based classification approach (36.17%). Thus, the ML classification is applicable for benthic habitat mapping in Padaido Islands. However, the consistency of this method must be analyzed in many diffrent locations of Indonesian waters.

A new, high-resolution global mass coral bleaching database.

Episodes of mass coral bleaching have been reported in recent decades and have raised concerns about the future of coral reefs on a warming planet. Despite the efforts to enhance and coordinate coral reef monitoring within and across countries, our knowledge of the geographic extent of mass coral bleaching over the past few decades is incomplete. Existing databases, like ReefBase, are limited by the voluntary nature of contributions, geographical biases in data collection, and the variations in the spatial scale of bleaching reports. In this study, we have developed the first-ever gridded, global-scale historical coral bleaching database. First, we conducted a targeted search for bleaching reports not included in ReefBase by personally contacting scientists and divers conducting monitoring in under-reported locations and by extracting data from the literature. This search increased the number of observed bleaching reports by 79%, from 4146 to 7429. Second, we employed spatial interpolation techniques to develop annual 0.04° × 0.04° latitude-longitude global maps of the probability that bleaching occurred for 1985 through 2010. Initial results indicate that the area of coral reefs with a more likely than not (>50%) or likely (>66%) probability of bleaching was eight times higher in the second half of the assessed time period, after the 1997/1998 El Niño. The results also indicate that annual maximum Degree Heating Weeks, a measure of thermal stress, for coral reefs with a high probability of bleaching increased over time. The database will help the scientific community more accurately assess the change in the frequency of mass coral bleaching events, validate methods of predicting mass coral bleaching, and test whether coral reefs are adjusting to rising ocean temperatures.

Responses of coral reef fishes to past climate changes are related to life-history traits.

Coral reefs and their associated fauna are largely impacted by ongoing climate change. Unravelling species responses to past climatic variations might provide clues on the consequence of ongoing changes. Here, we tested the relationship between changes in sea surface temperature and sea levels during the Quaternary and present‐day distributions of coral reef fish species. We investigated whether species‐specific responses are associated with life‐history traits. We collected a database of coral reef fish distribution together with life‐history traits for the Indo‐Pacific Ocean. We ran species distribution models (SDMs) on 3,725 tropical reef fish species using contemporary environmental factors together with a variable describing isolation from stable coral reef areas during the Quaternary. We quantified the variance explained independently by isolation from stable areas in the SDMs and related it to a set of species traits including body size and mobility. The variance purely explained by isolation from stable coral reef areas on the distribution of extant coral reef fish species largely varied across species. We observed a triangular relationship between the contribution of isolation from stable areas in the SDMs and body size. Species, whose distribution is more associated with historical changes, occurred predominantly in the Indo‐Australian archipelago, where the mean size of fish assemblages is the lowest. Our results suggest that the legacy of habitat changes of the Quaternary is still detectable in the extant distribution of many fish species, especially those with small body size and the most sedentary. Because they were the least able to colonize distant habitats in the past, fish species with smaller body size might have the most pronounced lags in tracking ongoing climate change.

The accuracy of the outer boundary delineation of coral reef area derived from the analyses of various vegetation indices of satellite landsat thematic mapper

Abstract. Sulistyo B. 2017. The accuracy of the outer boundary delineation of coral reef area derived from the analysis of various vegetation indices of satellite Landsat thematic mapper. Biodiversitas 18: 351-358. This research aimed at determining the accuracy of the outer boundary delineation of coral reef area derived from the analysis of various vegetation indices of satellite Landsat Thematic Mapper in Enggano Island, the District of North Bengkulu, Bengkulu Province. The vegetation indices of Landsat Thematic Mapper analyzed were the Ratio Vegetation Index, the Normalized Difference Vegetation Index, the Soil Adjusted Vegetation Index, the Transformed Soil Adjusted Vegetation Index, the Modified Soil Adjusted Vegetation Index and the Transformed Vegetation Index. The result of every analysis of vegetation index (index map) was then used as a base for on-screen digitization of the points assumed to be the outer boundary of coral reefs in order to get digital data. Digitization of shoreline was also done to create an inner boundary of coral reefs. When it is combined with its outer boundary then the calculation of the area is possible. The accuracy of the result was validated by overlaying it onto Map of Coral Reefs derived from a topographic map of Joint Operation Group. To justify whether the accuracy is good (or accepted) or not good (or not accepted), a threshold value proposed by Justice and Townshend was chosen, those are Poor (when the accuracy is &lt; 70%), Moderate (when the accuracy is between 70% and 85%), and Good (when the accuracy is ≥ 85%). The results of the research showed that the accuracy of RVI and NDVI values were Poor, those are 67.11% and 66.42%, respectively, so it could not be used for further analysis. The other results were Moderate, those are 73.33% for SAVI, 74.22% for TSAVI, 77.32 % for MSAVI and 77.33% for TVI, and may be used as a quick alternative when the map is absent.&#x0D; Keywords: coral reefs, Landsat, outer boundary delineation, vegetation index

Assessment of proposed approaches for bathymetry calculations using multispectral satellite images in shallow coastal/lake areas: a comparison of five models

Bathymetric information for shallow coastal/lake areas is essential for hydrological engineering applications such as sedimentary processes and coastal studies. Remotely sensed imagery is considered a time-effective, low-cost, and wide-coverage solution for bathymetric measurements. This study assesses the performance of three proposed empirical models for bathymetry calculations in three different areas: Alexandria port, Egypt, as an example of a low-turbidity deep water area with silt-sand bottom cover and a depth range of 10.5 m; the Lake Nubia entrance zone, Sudan, which is a highly turbid, unstable, clay bottom area with water depths to 6 m; and Shiraho, Ishigaki Island, Japan, a coral reef area with varied depths ranging up to 14 m. The proposed models are the ensemble regression tree-fitting algorithm using bagging (BAG), ensemble regression tree-fitting algorithm of least squares boosting (LSB), and support vector regression algorithm (SVR). Data from Landsat 8 and Spot 6 satellite images were used to assess the performance of the proposed models. The three models were used to obtain bathymetric maps using the reflectance of green, red, blue/red, and green/red band ratios. The results were compared with corresponding results yielded by two conventional empirical methods, the neural network (NN) and the Lyzenga generalised linear model (GLM). Compared with echosounder data, BAG, LSB, and SVR results demonstrate higher accuracy ranges from 0.04 to 0.35 m more than Lyzenga GLM. The BAG algorithm, producing the most accurate results, proved to be the preferable algorithm for bathymetry calculation.

Diversity of Ecosystem Types in India: A Review

India is home to an unusually large number of endemic species and ranks sixth among the 12 megabiodiversity centers of the world. Four terrestrial biodiversity hot spots (Himalaya, Indo-Burma, Western Ghats and Sri Lanka, and Sundaland) partly lie in India. The 27 distinct biogeographic provinces, and the variety of life zones and floral groups result in equally diverse vegetation and ecosystem types. The forest ecosystems are markedly diverse and have been classified into six ‘major groups’ ranging from tropical to alpine, 16 ‘groups’ and more than 200 ‘group categories’. The grassland ecosystems are categorized into five major grass cover types. There are 1193 wetlands covering a total area of 3.9 million hectares in 274 districts. Total area of coral reefs comprises 2,375 sq km. India is one of the eight Vavilov’s centers of origin of cultivated plants in the world and has twenty distinct agro-ecosystems, characterized by variations in edaphic, climatic and geographic features, and consequently a diverse cropping pattern. In this article we give an overview of the vast array of broad ecosystem types that occur in India. We also briefly discuss the human impacts on the health of country’ s ecosystems and the ecosystem conservation scenario.

Seafloor Characterization and Backscatter Variability of Coral Reef by Different Acoustic Techniques, El-Gouna, Red Sea, Egypt

Seabed sediment classification is an important research study for marine geology, marine environment and other research areas. The study area located at 25 km North of Hurghada. This study aims at identification of sea bed sediments and coral reef habitat of El-Gouna Area. Side scan sonar and QTC system used for surveying the area. Detection of the destroyed coral reef areas depends on the acoustic backscatter and diving survey along the study area. The sea floor sediment types, features and the biological habitats were the main causes that control the acoustic signature in the study area. The main seabed sediment types in the study area were hard bottom representing the coral reef patches, coarse and fine sand fractions. Overall, the acoustic approach showed consistent results for the assessment and mapping of the benthic habitats in this shallow-water area. Three different acoustic patterns were recognized: pattern of strong backscatter related to coarse sand, while Pattern of weak backscatter confined to silt and fine sand, patches of strong and weak backscatter are Patterns with isolated reflections belong to hard and soft coral reefs.

American Samoa's Marine Protected Area System: Institutions, Governance, and Scale

Marine protected areas (MPAs) are a primary marine conservation strategy in the US territory of American Samoa, which has a goal to protect 20 percent of its coral reef area under “no-take” MPAs. T...