Distribution Patterns Of Corals Research Articles

Diversity patterns of the South African azooxanthellate scleractinians (Cnidaria: Anthozoa), with considerations of environmental correlates.

Azooxanthellate scleractinian corals, a group of species that lack a symbiotic relationship with dinoflagellates, are influenced by environmental variables at various scales. As the global commitment to sustainably manage ocean ecosystems and resources rises, there is a growing need to describe biodiversity trends in previously unsampled areas. Benthic invertebrate research in South Africa is a developing field, and many taxa in deep water environments remain inadequately characterized. Recently, the South African azooxanthellate scleractinian fauna was taxonomically reviewed, but their distributional correlations with physical parameters have not been studied. Here we aim to understand the biodiversity gradients of the South African azooxanthellate coral fauna by analysing the environmental correlates of museum samples. The associated coordinate data were georeferenced and depth obtained from a national bathymetric dataset, prior to undertaking a multivariate analysis. This analysis encompassed several steps, including the grouping of the longitude and depth data (environmental data), identifying families characteristic of the group variability, and examining the correlation of the associated data with the biological data. Additionally, the analysis involved quantifying diversity patterns along the environmental gradients. Overall, our results confirmed two longitudinal groups (eastern margin [Group A] vs southern and western margin [Group B]) and 11 depth categories represented within two bathymetric zones (shallow [50-200 m] and deep [300-1000 m]). Caryophylliids, flabellids, and dendrophylliids contributed the most towards distinguishing longitudinal and depth gradients. Both abiotic variable (longitudinal and depth) partially explained coral distribution patterns, with depth being highly correlated to the species variation observed. Data limitations within our data set resulted to unexplained variance, however, despite these limitations, the study demonstrates that historical museum samples provide a valuable data source that can fill research sampling gaps and help improve the understanding of biodiversity patterns of the coral fauna in under sampled marine ecosystems.

Unveiling deep-sea habitats of the Southern Ocean-facing submarine canyons of southwestern Australia

Here we present the outcomes of the first deep-sea remotely operated vehicle study of previously unexplored submarine canyon systems along the southwest Australian continental margin. This was conducted around: (1) the Bremer Marine Park; (2) the Mount Gabi seamount and nearby slope-shelf margin at the interface of the Southern and Indian oceans; with new information from (3) the Perth Canyon Marine Park located in the SE Indian Ocean. These canyons differ from many explored around the world in having no connectivity to continental river systems, thus little detrital input, with the Bremer systems and Mount Gabi facing the Southern Ocean which plays a key role in the global ocean circulation and climate systems. Such studies in the vast deep waters around the Australian continent are rare given the lack of local ROV capability available for research, thus little is known about these environments.Using the resources of the Schmidt Ocean Institute, we characterised the submarine topography from high-resolution bathymetric mapping, geology, physical and chemical oceanography, and provide an overview of these environments including the fauna observed and collected. We show that these Southern Ocean-influenced environments incorporate South Indian Central Water, Subantarctic Mode Water, Antarctic Intermediate Water, and Upper and Lower Circumpolar Deep Water, with Antarctic Bottom Water present in deep water just south of the Bremer canyon systems. The richness in megabenthos, especially along the steep, rocky substrates of the canyon heads and walls around the Bremer canyon systems, contrasts to the comparatively depauperate fauna of the more northerly Perth Canyon. Various corals serve as important substrates for a range of other species and often exhibit particular faunal associations. Especially notable are distinct ecological zones including a bryozoan and sponge-dominated (animal) forest on the shelf edge, spectacular coral gardens along canyon margins, and the occurrence of solitary scleractinians well below the aragonite saturation horizon. Subfossil coral deposits were discovered across all three study areas, reflecting periodic waxing and waning of deep-water Scleractinia throughout this southwest region. Extensive pre-modern assemblages at Mount Gabi contrast markedly with the sparse populations of living species and suggest that it might have once been a major coral hotspot, or whether they reflect long-term coral aggregations is yet to be determined. Nevertheless, stark differences in both living and past coral distribution patterns across our study sites point to at least localised fluctuations in Southern Ocean-derived nutrient and/or oxygen supplies to these deep-sea communities.

Coral Community: Preliminary Biodiversity Survey of Churna Island, Northern Arabian Sea

Biodiversity survey between Cape Monze and Churna Island was carried out for the assessment of coral assemblages in the area. During the present study, diving surveys were conducted to document the living corals that included deep sea coral, Coelenterates, Bryozoans, Gorgonia (Sea Fan), Scleractinian, (Stony Corals) Cnidaria (Hydroids), Porites (Small Polyp Stony), Pocilopora (Cauliflower Corals), Acropora (Hard Corals), sea urchins, sea anemones, coral fish spp, sea slugs, stone fish and bivalves were observed and documented. To have a better understanding of the distribution pattern “Shannon Weiner Biodiversity Index” for species diversity “H” (0.845-1.176) and evenness “J” (0.962-0.937) were calculated, the values indicate that the coral species were evenly distributed and did not show any significant variation in the area. Budding coral communities were observed at the sedimentary rock of Churna in patches, and showed a random distribution behavior all along the surveyed area. Random, scattered and aggregate distribution patterns of corals may be due to the wave beaten physical environment of Churna Island that do not allow sustainable growth of coral communities. Moreover, the high energy waves and water currents destablize and erode the sedimentary substrate on which corals grow. The corals are therefore unable to establish themselves to form a natural reef due to loss of natural living and non-living substrate. The ecology of Churna Island also under the influence of nearby coastal industries, and the Hub River influx causing floods in the SW monsoon period that may destablize rubble and increase the seawater turbidity level. These environmental factors contributing to the deterioration of present day corals, and larval settlement. It may be concluded that biological resources are renewable and can even increase with proper management techniques. Breakwater wall and artificial substrate must be encouraged to further facilitate the growth and development of Corals in the area.

Coral Community: Preliminary Biodiversity Survey of Churna Island, Northern Arabian Sea

Biodiversity survey between Cape Monze and Churna Island was carried out for the assessment of coral assemblages in the area. During the present study, diving surveys were conducted to document the living corals that included deep sea coral, Coelenterates, Bryozoans, Gorgonia (Sea Fan), Scleractinian, (Stony Corals) Cnidaria (Hydroids), Porites (Small Polyp Stony), Pocilopora (Cauliflower Corals), Acropora (Hard Corals), sea urchins, sea anemones, coral fish spp, sea slugs, stone fish and bivalves were observed and documented. To have a better understanding of the distribution pattern “Shannon Weiner Biodiversity Index” for species diversity “H” (0.845-1.176) and evenness “J” (0.962-0.937) were calculated, the values indicate that the coral species were evenly distributed and did not show any significant variation in the area. Budding coral communities were observed at the sedimentary rock of Churna in patches, and showed a random distribution behavior all along the surveyed area. Random, scattered and aggregate distribution patterns of corals may be due to the wave beaten physical environment of Churna Island that do not allow sustainable growth of coral communities. Moreover, the high energy waves and water currents destablize and erode the sedimentary substrate on which corals grow. The corals are therefore unable to establish themselves to form a natural reef due to loss of natural living and non-living substrate. The ecology of Churna Island also under the influence of nearby coastal industries, and the Hub River influx causing floods in the SW monsoon period that may destablize rubble and increase the seawater turbidity level. These environmental factors contributing to the deterioration of present day corals, and larval settlement. It may be concluded that biological resources are renewable and can even increase with proper management techniques. Breakwater wall and artificial substrate must be encouraged to further facilitate the growth and development of Corals in the area.

Cold-Water Corals and Anthropogenic Impacts in La Fonera Submarine Canyon Head, Northwestern Mediterranean Sea.

We assess the occurrence and extent of cold-water coral (CWC) species Madrepora oculata and Dendrophyllia cornigera, as well as gorgonian red coral Corallium rubrum, in La Fonera canyon head (Northwestern Mediterranean Sea), as well as human impacts taking place in their habitats. Occurrence is assessed based on Remotely Operated Vehicle (ROV) video imaging. Terrain classification techniques are applied to high-resolution swath bathymetric data to obtain semi-automatic interpretative maps to identify the relationship between coral distribution patterns and canyon environments. A total of 21 ROV immersions were carried out in different canyon environments at depths ranging between 79 and 401 m. Large, healthy colonies of M. oculata occur on abrupt, protected, often overhanging, rocky sections of the canyon walls, especially in Illa Negra branch. D. cornigera is sparser and evenly distributed at depth, on relatively low sloping areas, in rocky but also partially sedimented areas. C. rubrum is most frequent between 100 and 160 m on highly sloping rocky areas. The probable extent of CWC habitats is quantified by applying a maximum entropy model to predict habitat suitability: 0.36 km2 yield M. oculata occurrence probabilities over 70%. Similar predictive models have been produced for D. cornigera and C. rubrum. All ROV transects document either the presence of litter on the seafloor or pervasive trawling marks. Nets and longlines are imaged entangled on coral colonies. Coral rubble is observed at the foot of impacted colonies. Some colonies are partially covered by sediment that could be the result of the resuspension generated by bottom trawling on neighbouring fishing grounds, which has been demonstrated to be responsible of daily increases in sediment fluxes within the canyon. The characteristics of the CWC community in La Fonera canyon are indicative that it withstands high environmental stress of both natural and human origin.

Predicting the distribution of deep-sea vulnerable marine ecosystems using high-resolution data: Considerations and novel approaches

Little is known about species distribution patterns in deep-sea environments, primarily because sampling surveys in the high seas are expensive and time consuming. The increasing need to manage and protect vulnerable marine ecosystems, such as cold-water corals, has motivated the use of predictive modelling tools, which produce continuous maps of potential species or habitat distribution from limited point observations and full coverage environmental data. Rapid advances in acoustic remote sensing, oceanographic modelling and sampling technology now provide high quality datasets, facilitating model development with high spatial detail. This paper provides a short overview of existing methodologies for predicting deep-sea benthic species distribution, and illustrates emerging issues related to spatial and thematic data resolution, and the use of transect-derived species distribution data. In order to enhance the ecological relevance and reliability of deep-sea species distribution models, novel techniques are presented based on a case study predicting the distribution of the cold-water coral Lophelia pertusa in three carbonate mound provinces in Irish waters. Specifically, the study evaluates (1) the capacity of newly developed high-resolution (250m grid cell size) hydrodynamic variables to explain local scale cold-water coral distribution patterns, (2) the potential value of species occurrence proportion data to maintain semi-quantitative information of coral prevalence (i.e. coverage) and sampling effort per grid cell within the response variable, and (3) mixed effect modelling to deal with spatially grouped transect data. The study shows that predictive models using vertical and horizontal flow parameters perform significantly better than models based on terrain parameters only. Semi-quantitative proportion data may decrease model uncertainty and increase model reliability, and provide a fruitful avenue of research for analysing large quantities of video data in a detailed yet time-efficient manner. The study concludes with an outlook of how species distribution models could improve our understanding of vulnerable marine ecosystem functioning and processes in the deep sea.

Environmental variabilities and the distribution of octocorals and black corals in Hong Kong

A recent comprehensive survey covering 125 sites in Hong Kong waters recorded 29 soft coral species in 14 genera, 38 species of gorgonians in 19 genera and six species of black corals in two genera. Environmental variabilities based on water quality data collected by Hong Kong Environmental Protection Department were analyzed using multivariate statistics to find variables that are significantly correlated with coral distribution patterns. Eleven water quality zones with similar environmental variabilities were recognized, which could further be classified into five groups, namely Inner Bay, Outer Bay, Eastern, Western and Southern waters. LINKTREE analysis provided an overall trend indicating the importance of salinity, sediment and nutrient loadings in affecting octocoral and black coral distribution from west to east of Hong Kong waters, and from inner to outer bays. Furthermore, water turbidity and wave exposure could also affect the coral distribution patterns from north, northeast to southern waters.

Spatial differentiation of coral species related to wave energy along the Changqi coast, Hainan island, southern China

The regularities of the composition and the spatial distribution of hermatypic coral community is an essential aspect of coral reef ecosystem studies. The relationship between the structure and spatial distribution of hermatypic coral communities and hydrodynamics and wave energy, along the Changqi coast, are investigated. Differences in abundance of hermatypic coral species, at different depths, were found; these were related mainly to the varying influence of waves. Under average weather conditions, the wave energy was dissipated regularly at a depth of 2m. Here, the coral cover was the lowest of all of the depths. However, corals growing in that area is adapted to the conditions; therefore, wave damage was low. The areas at 5–6m water depth were influenced by waves primarily during episodes of extreme weather, with high wave energy resulting in severe damage of the corals. The coral cover in this depth was the highest observed, but the corals were generally smaller and had a short growth period. These findings indicate that the strong waves damaged particularly the weak corals, such as Acropora sp. and Montipora sp., during these short term events. Nevertheless, upon the return of normal conditions, coral communities can grow back and reproduce asexually in the damaged areas. As a result of this regrowth, Acropora sp. and Montipora sp. were highly abundant in areas at a depth of 5m. It appears that knowledge on the physical setting, i.e. the relationship between wave properties and the spatial distribution patterns of corals, is essential for understanding coral reef succession rules; likewise, protection and recovery mechanisms of the coral reef ecosystem.

サンゴ礁と造礁サンゴを用いた完新世の高精度海面変動復元にむけて

The importance of Holocene sea-level change has long been a central theme of Quaternary Science. Holocene sea-level records provide direct evidence of the progress of the melting of the ice sheet during the Holocene. Although the correlation between ice and ocean volumes is incontrovertible, casual links are commonly obscured. Some regional studies of coral-reef sites based on analyses of boring cores have been carried out from reef flat to reef slope at present-day reefs, demonstrating a long-term (1000-10000 years) and large-amplitude (10-100 m) melt-water history. However, short-term (< 100 years) and small-scale (< 1 m) sea-level changes that detail past sea-level records and play a major role in predicting sea-level fluctuations in the near future are not observed from reef cores. This paper is based principally on a re-examination of sea-level records from the literature and presents the following suggestions to reconstruct high-resolution Holocene sea-level records: (1) Identifying species from boring core samples is effective to reconstruct sea-level changes more precisely during the Holocene. (2) Relative abundance of data for each species is essential to determine position and course of sea-level curve within the envelope of their living depths. (3) The accuracy of reconstructing the sea-level record depends on the distribution pattern of corals; the vertical distribution in a present-day reef obtained from a site close to a given boring site is all that is required. The sea-level curve based on agreement with the above requirement is characterized by smaller fluctuations (±0.5 - ±2.5 m) during the Holocene, thus studies on the high-resolution sea-level record will provide predictions for research on the spatial and temporal histories of sea-level change to Holocene sciences and management of conservation of land in the near future.

Human Impacts on Coral Reefs in the Sultanate of Oman

A rapid assessment survey of the coral reefs of the Sultanate of Oman was conducted by the Ministry of Regional Municipalities and Environment during the first half of 1996. The survey revealed new information on the distribution pattern of corals in Oman and identified impacts, threats and potential threats to coral communities for the purpose of preparation of a National Coral Reef Management Plan (Phase One of the implementation of a National Coastal Zone Management Plan). Impacts on coral reefs in Oman were found to be attributable to both natural and human causes, resulting in significant and widespread degradation. Damage resulting from fisheries activities was the most commonly recorded human impact, with the most severe effects. Other human impacts resulted from coastal construction, recreational activities, oil pollution and eutrophication. Predation of corals by Acanthaster planci, damage caused by storms, coral diseases and temperature-related stress were the most commonly recorded natural impacts to coral reefs. Further minor natural impacts were attributable to siltation, rock falls and predation by a corallivorous gastropod (Drupella sp.). Significant differences between different areas of the country were found in terms of human impacts on coral reefs and these were related to coastal demography and human activity. Eighty per cent of sites studied were recorded to have been affected by human impacts to some degree. Impacts attributable to fisheries activities were found at 69% of the sites. Lost or abandoned gill nets were found to affect coral reefs at 49% of sites throughout Oman and accounted for 70% of all severe human impacts. Lost gill nets were also found to have a negative affect on fisheries resources and other marine wildlife. Observations of the behaviour of gill nets on coral reefs suggested a predictable pattern of damage over time and a significant increase in damage intensity during storms. Fishing nets were found to act selectively, causing greater damage to certain coral communities than to others. Results of the study are discussed in relation to management of coral reef areas in Oman.

Pleistocene reef environments, constituent grains, and coral community structure: Curaçao, Netherlands Antilles

We investigated the degree to which component grains vary with depositional environment in sediments from three reef habitats from the Pleistocene (125 ka) Hate Unit of the Lower Terrace, Curacao, Netherlands Antilles: windward reef crest, windward back reef, and leeward reef crest. The windward reef crest sediment is the most distinctive, dominated by fragments of encrusting and branching coralline red algae, coral fragments and the encrusting foraminiferan Carpenteria sp. Windward back reef and leeward reef crest sediments are more similar compositionally, only showing significant differences in relative abundance of coral fragments and Homotrema rubrum. Although lacking high taxonomic resolution and subject to modification by transport, relative abundance of constituent grain types offers a way of assessing ancient skeletal reef community composition, and one which is not limited to a single taxonomic group. The strong correlation between grain type and environment we found in the Pleistocene of Curacao suggests that constituent grain analysis may be an effective tool in delineating Pleistocene Caribbean reef environments. However, it will not be a sufficient indicator where communities vary significantly within reef environments or where evolutionary and/or biogeographical processes lead to different relationships between community composition and reef environment. Detailed interpretation of geological, biological, and physical characteristics of the Pleistocene reefs of Curacao reveals that the abundance of the single coral species, Acropora palmata, is not a good predictor of the ecological structure of the ancient reef coral communities. This coral was the predominant species in two of the three reef habitats (windward and leeward reef crest), but the taxonomic composition (based on species relative abundance data) of the reef coral communities was substantially different in these two environments. We conclude that qualitative estimates of coral distribution patterns (presence of a key coral species or the use of a distinctive coral skeletal architecture), when used as a component in a multi-component analysis of ancient reef environments, probably introduces minimal circular reasoning into quantitative paleoecological studies of reef coral community structure.

Patterns of Coral Distribution and Benthic Space Partitioning on the Fringing Reefs of Southern Taiwan

Abstract. The distribution pattern of corals and benthic space partitioning patterns on the fringing reefs of southern Taiwan were studied by the line‐transect method. The bathymetric distribution of corals in the study area was basically homogeneous except on the protected reef slopes and the exposed reef fronts and terraces. Corals on protected reef slopes are mainly foliaceous, including Montipora foliosa, Merulina ampliata, Mycedium elephantotus, and Pachyseris speciosa, but the dominant species on a reef slope vary from site to site. The formation of the foliaceous coral community is possibly related to a complex of environmental factors, chance, and biological interactions. The reef fronts and submarine terraces of exposed areas are dominated by alcyonacean corals. The most abundant species are Sarcophyton trocheliophorum, S. crassocaule, and Lobophytum sarcophytoides; their distributions are relatively homogeneous. The formation of alcyonacean‐dominated assemblages can be related to the special adaptive strategies of these corals. In regard to space partitioning patterns, the major space occupiers on those reefs exposed to storm disturbances are alcyonacean soft corals, scleractinian corals, and algae; on reefs protected from storms, scleractinian corals and algae dominate. Two conspicuous features of the study area are the high proportion of space occupied by algae and the abundant unoccupied space. The dense algal cover is possibly caused by sewage pollution and overfishing of the reef area. The unoccupied space is most likely related to the high frequency of typhoon disturbances.

Coral Distribution Patterns in Miocene Reefs of Anguilla, Leeward Islands, West Indies: ABSTRACT

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