Recent benthic foraminiferal assemblages from cold-water coral mounds in the Porcupine Seabight

Cold-water coral ecosystems are characterised by a high diversity and population density. Living and dead foraminiferal assemblages from 20 surface sediment samples from Galway and Propeller Mounds were analysed to describe the distribution patterns of benthic foraminifera on coral mounds in relation to different sedimentary facies. Hard substrates were examined to assess the foraminiferal microhabitats and diversities in the coral framework. We recognised 131 different species, of which 27 prefer an attached lifestyle. Epibenthic species are the main constituents of the living and dead foraminiferal assemblages. The frequent species Discanomalina coronata was associated with coral rubble, Cibicides refulgens showed preference to the off-mound sand veneer, and Uvigerina mediterranea displayed abundance maxima in the main depositional area on the southern flank of Galway Mound, and in the muds around Propeller Mound. The distribution of these species is rather governed by their specific ecological demands and microhabitat availability than by the sedimentary facies. Benthic foraminiferal assemblages from coral mounds fit well into basin-wide-scale distribution patterns of species along the western European continental margin. The diversity of the foraminiferal faunas is not higher on the carbonate mounds as in their vicinity. The living assemblages show a broad mid-slope diversity maximum between 500 and 1,300 m water depth, which is the depth interval of coral mound formation at the Celtic and Amorican Margin. The foraminiferal diversity maximum is about 700 m shallower than comparable maxima of nematodes and bivalves. This suggests that different processes are driving the foraminiferal and metazoan diversity patterns.     

Effect of habitat complexity on population density and species richness in tropical intertidal predatory gastropod assemblages

Summary Structural complexity of the habitat significantly increases population density and number of species in assemblages of predatory gastropod molluscs (families Conidae, Muricidae, Mitridae and Vasidae) on intertidal, generally smooth, horizontal limestone platforms fringing tropical Pacific islands. The important topographic features are physical (depressions partly filled with coral rubble) and biotic (thick algal turf binding sand). Higher population density and species richness in areas with than without such natural refuges, and following experimental addition of artificial refuges on portions of habitat lacking them support this hypothesis. Two species of Drupa differ from the other species present in not utilizing refuges during times of physical stress; this is attributed to their depressed shell and broad, tenacious foot. Highest gastropod densities occur in steep-sided depressions and those containing much coral rubble and sand, suggesting that these are important qualities of refuges. We believe this is the first demonstration of how specific environmental factors affect population density and species diversity of benthic invertebrates in a coral reef-associated habitat.     

Reach- and catchment-scale determinants of the distribution of freshwater mussels (Bivalvia: Unionidae) in south-eastern Michigan, U.S.A.

1. We investigated the diversity and distribution of freshwater mussels at 40 sites in an agricultural catchment, the River Raisin in south‐eastern Michigan, to relate mussel assemblages and individual taxa to reach and catchment‐scale variables. Unionids were surveyed by timed searches in 100‐m reaches, and in‐stream and riparian habitat were quantified as well as flow, water chemistry and channel morphology. Land use/cover and surficial geology were determined for site subcatchments and riparian buffers. 2. Some 21 mussel species were found overall; richness ranged from 0 to 12 living species per site. From the upper to middle to lower catchment, the number of individuals, number of species, Shannon–Weaver diversity and relative abundance of intolerant unionids all declined significantly. 3. Four groupings based on overall mussel diversity and abundance were significantly related to reach‐scale habitat variables. The richest mussel assemblages were associated with sites with higher overall habitat quality, greater flow stability, less fine substratum, and lower specific conductance. 4. Stepwise multiple regressions revealed that the distribution and abundance of the total mussel assemblage, as well as the most common species, could be predicted from a combination of reach‐ and catchment‐scale variables (R² = 0.63 for total mussels, R² = 0.51–0.86 for individual species). 5. Flow stability, substratum composition and overall reach habitat quality were the most commonly identified reach‐scale variables, and measures of surficial geology were the most effective catchment‐scale variables. The spatial pattern of geology is likely to be responsible for the diversity gradient from the upper to the lower catchment. 6. Prior studies, attempting to explain mussel distributions from local habitat features alone, have found relatively weak relationships. By employing a combination of reach‐ and catchment‐scale habitat variables, this study was able to account for a substantial amount of the spatial variability in mussel distributions.     

Polychaete populations of the shallow soft bottoms off Terra Nova Bay (Ross Sea, Antarctica): distribution, diversity and biomass

 Diversity, distribution and biomass patterns of polychaetes were studied in the shallow soft bottoms off Terra Nova Bay (Ross Sea, Antarctica). Benthic samples, collected in the austral summer 1989–1990, were sampled using a Van Veen grab at 14 stations distributed between 23- and 194-m depth. A total of 5,768 individuals of polychaetes belonging to 77 species were found. The species richness recorded was high, despite the few biotopes investigated at Terra Nova Bay in this study, especially when compared to that recorded from previous investigations in the same area and from the whole Ross Sea (146 species). Despite the high number of species found, only a few species accounted for 76% of the total abundance: Tharyx cincinnatus (27%), Spiophanes tcherniai (23%), Leitoscoloplos mawsoni (18%) and Laonice weddellia (5%) were mainly distributed in the deeper stations (below 100-m depth), while Aglaophamus ornatus (3%) was the only species abundant in the shallowest stations (above 50-m depth), characterized by gravels and coarse sands. Species richness, diversity and evenness showed an increase with depth. Abundances ranged between 40 to over 12,000 ind/m². Biomass values ranged between 0.9 to 176 g/m² (wet weight). A trophic-guild classification revealed the occurrence of various feeding categories that were, however, numerically dominated by deposit feeders with both discretely motile epiand endobenthic forms, and sessile ones. Both the Bray-Curtis similarity and Correspondence (C.A.) analyses showed stations ordered according to depth and to the local dominance of some species. Both poorly and well-structured polychaete assemblages occurred and they seemed related to depth-related factors, such as degree of environmental disturbance (shallowest bottoms vs deep ones), heterogeneity of the substrate and habitat complexity (gravel and coarse sands vs mixed sediment. The richest and most diverse assemblages of polychaetes were those occurring below 140-m depth, where the substrate was dominated by medium sands, often mixed with a mosaic of rocks and boulders. Received: 30 October 1995/Accepted: 1 May 1996     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

Relative Importance of Coral Cover,Habitat Complexity and Diversity in Determining the Structure of Reef Fish Communities

The structure of coral reef habitat has a pronounced influence on the diversity, composition and abundance of reef-associated fishes. However, the particular features of the habitat that are most critical are not always known. Coral habitats can vary in many characteristics, notably live coral cover, topographic complexity and coral diversity, but the relative effects of these habitat characteristics are often not distinguished. Here, we investigate the strength of the relationships between these habitat features and local fish diversity, abundance and community structure in the lagoon of Lizard Island, Great Barrier Reef. In a spatial comparison using sixty-six 2m² quadrats, fish species richness, total abundance and community structure were examined in relation to a wide range of habitat variables, including topographic complexity, habitat diversity, coral diversity, coral species richness, hard coral cover, branching coral cover and the cover of corymbose corals. Fish species richness and total abundance were strongly associated with coral species richness and cover, but only weakly associated with topographic complexity. Regression tree analysis showed that coral species richness accounted for most of the variation in fish species richness (63.6%), while hard coral cover explained more variation in total fish abundance (17.4%), than any other variable. In contrast, topographic complexity accounted for little spatial variation in reef fish assemblages. In degrading coral reef environments, the potential effects of loss of coral cover and topographic complexity are often emphasized, but these findings suggest that reduced coral biodiversity may ultimately have an equal, or greater, impact on reef-associated fish communities.     

Impact of cyclones on hard coral and metapopulation structure,connectivity and genetic diversity of coral reef fish

Cyclones have one of the greatest effects on the biodiversity of coral reefs and the associated species. But it is unknown how stochastic alterations in habitat structure influence metapopulation structure, connectivity and genetic diversity. From 1993 to 2018, the reefs of the Capricorn Bunker Reef group in the southern part of the Great Barrier Reef were impacted by three tropical cyclones including cyclone Hamish (2009, category 5). This resulted in substantial loss of live habitat-forming coral and coral reef fish communities. Within 6–8 years after cyclones had devastated, live hard corals recovered by 50–60%. We show the relationship between hard coral cover and the abundance of the neon damselfish (Pomacentrus coelestis), the first fish colonizing destroyed reefs. We present the first long-term (2008–2015 years corresponding to 16–24 generations of P. coelestis) population genetic study to understand the impact of cyclones on the meta-population structure, connectivity and genetic diversity of the neon damselfish. After the cyclone, we observed the largest change in the genetic structure at reef populations compared to other years. Simultaneously, allelic richness of genetic microsatellite markers dropped indicating a great loss of genetic diversity, which increased again in subsequent years. Over years, metapopulation dynamics were characterized by high connectivity among fish populations associated with the Capricorn Bunker reefs (2200 km²); however, despite high exchange, genetic patchiness was observed with annual strong genetic divergence between populations among reefs. Some broad similarities in the genetic structure in 2015 could be explained by dispersal from a source reef and the related expansion of local populations. This study has shown that alternating cyclone-driven changes and subsequent recovery phases of coral habitat can greatly influence patterns of reef fish connectivity. The frequency of disturbances determines abundance of fish and genetic diversity within species.

     

A high local species richness and biodiversity within high-latitude calcareous aggregates of tube-building polychaetes

In general, biodiversity and species richness follow the latitudinal diversity gradient and decrease from the tropics towards the poles. Exceptions have however been recorded, as for deep coldwater coral reefs at high latitudes, which comprise biodiversity hotspots. Here we assess and characterise the high-latitude (69°N) species richness and diversity of a local shallow-water fauna associated with small calcareous aggregations of a serpulid polychaete. A dense and very species rich fauna was recorded within aggregations of Filograna implexa Berkeley, 1828. Totally 4663 individuals belonging to 99 species (61 solitary, 38 colonial) were recorded in a total aggregation volume of only 4.4 l covering an area less than 0.05 m² of a wreck situated in a tidal stream in North Norway. The number of species within each aggregation was positively related to its size, indicating that the high species diversity may be due to structural heterogeneity, which increase with aggregation size and probably creates new microhabitats and protect against predation. We present a species list including abundance and biomass, pin-point common species and describe a method for sampling such faunas associated with calcareous structures.     

Scleractinian coral recruitment patterns at Salt River submarine canyon,St. Croix,U.S. Virgin Islands

Scleractinian coral recruitment patterns were studied at depths of 9, 18, 27 and 37 m on the east and west walls of Salt River submarine canyon, St. Croix, U.S. Virgin Islands, by censusing coral juveniles which settled on experimental settling plates placed on the reef for 3–26 months as well as coral juveniles within quadrats on the reef. The most common species in the juvenile population within quadrats were Agaricia agaricites, Porites astreoides, Madracis decactis, Stephanocoenia michelinii, and A. lamarcki. The only species settling on settling plates were Agaricia spp., Madracis decactis, Porites spp., Stephanocoenia michelinii and Favia fragum. A total of 271 corals settled on 342 plates, with 51% of the juveniles on the east wall and 49% on the west wall. Of these 34% settled on horizontal surfaces and 66% on vertical surfaces. Based on results from quadrats, Agaricia agaricites and Porites astreoides had high recruitment rates relative to their abundance on the reef. In contrast, Agaricia lamarcki, Montastraea annularis, M. cavernosa and Siderastrea siderea had high amounts of cover compared to their abundance as juveniles within quadrats. The mean number of juveniles per m² within quadrats ranged from 3 to 42. In general, there was a decrease in the mean number of juveniles and the number of species with depth. Total number of juveniles on settling plates was highest at 18 m on both walls. The largest number within quadrats was at 18 m on the east wall, followed by 9 m and 18 m on the west wall. High rates of coral recruitment tended to be associated with low algal biomass and relatively high grazing pressure by urchins and fishes.     

Coastal sponge communities of the West Indian Ocean: taxonomic affinities, richness and diversity

Sponges assemblages were sampled in four coastal study regions (Malindi, Kenya; Quirimba Archipelago, northern Mozambique; Inhaca Island, Southern Mozambique and Anakao, Madagascar) in the west Indian Ocean. Sponge species were counted in multiple 0.5 m² quadrats at depths of between 0 and 20 m at a number of sites within localities within each region. Despite the relatively small areas sampled, sponge samples comprised a total of 130 species and 70 genera of the classes Demospongiae and Calcarea. Sponges are clearly a major taxon in these regions in terms of numbers of species, percentage cover or biomass, although their ecology in the west Indian Ocean is virtually unknown. Nearly half of the genera, e.g. Iotrochota, found were species with a so‐called Tethyan distribution. Most of the other genera were cosmopolitan, e.g. Clathria, but some were cold water (Coelosphaera), Indo‐Australian (Ianthella) or circum‐African (Crambe). Many of the species encountered in the present study occurred in at least two study regions, many in more and could occupy large areas of substratum. Some of these, e.g. Xestospongia exigua, are commonly found throughout the Indo‐west Pacific region where they also occupy much space. The endemicity of the shallow water sponge faunas in East Africa (20–25%) seem to be high within the Indo‐Pacific realm but are lower than northern Papua New Guinea. The tropical regions (Kenya and Northern Mozambique) were more speciose than subtropical regions (southern Mozambique and Madagascar) but not significantly more diverse (Shannon H′). Although latitude was not a major influence on sponge community patterns, hard substratum assemblages did form a cline from the tropics to Southern Mozambique, linked by Madagascar. Substratum nature (habitat) was most important in influencing the suite and number of species present. Sponge assemblages of soft substrata were much more dissimilar, both within and between habitats, than those on hard substrata. There was a predictable variability in species richness between hard substratum habitats: coral reefs being speciose and caves being less so. Our findings showed that both patterns and influences on species richness may be decoupled from those influencing diversity. In our data species richness, but not diversity, showed striking regional and bathymetric trends. In addition, sponge species richness mainly split at coral reef vs. non‐reef habitats, whilst diversity divided principally into assemblages on hard and soft substrata. We consider this dichotomy of findings between species richness and diversity values to be important, as these are two principal measures used for the interpretation of biodiversity.     

Assessment of site specific benthic impact of floating cage farming in the eastern Hios island, Eastern Aegean Sea, Greece

The site specific impact on the benthic fauna was assessed within a 4.64 km² area of intensive aquaculture situated on the eastern side of Hios island (Aegean Sea, Greece) at 11 stations seasonally between November 2000 and October 2001. The benthic fauna showed marked changes in species numbers, diversity and faunal abundance between farm and control sites. The polychaetes Nereis diversicolor, Scolelepis fuliginosa and Capitella capitata were the most dominant species at the farm sites (35% of the total abundance), whilst the most dominant species at the control sites were the polychaete Hyalinoecia brementi and the sipunculid Aspidosiphon muelleri (23% of the total abundance). Species richness, diversity and evenness were higher at the control sites whereas numerical abundance was higher at the farm sites. K-dominance curves suggest a minor impact on the benthic community at the farm sites and temporal changes on macrobenthic assemblages.     

Anthropogenic Disturbance on Shallow Cryptofaunal Communities in a Marine Life Conservation District on Oahu,Hawaii

Cryptic invertebrate communities in coral rubble and sand from Hanauma Bay, a Marine Life Conservation District, were analyzed. Substratum samples were collected from the shallow bench and sand channels next to the beach and the cryptofauna were examined. Sand from the shallows (0.6 m deep) is frequently trampled by beach users and has a depauperate community dominated by a polychaete (Saccocirrus alanhongi) and a variety of nematodes (mean no. taxa = 12, mean no. individuals = 1,143 (0.1 m^–2), but sand collected 25 m seaward from below trampling depths (3 m). showed significantly greater diversity (mean no. taxa = 46, mean no. individuals = 6,448 (0.1 m^–2). Coralline rubble from 0.5 m depth was acid dissolved to extract the cryptofauna that was trapped on 0.5 and 0.25 mm sieves. In total, 102 taxa and 10,673 individual invertebrates (0.1 m^–2) were found. Rubble collected from areas used by waders had a greater diversity than sand habitats. This substratum provides a greater variety of microhabitats and protection from trampling for endolithic fauna than sand. Waders may actively avoid rubble because of the discomfort from walking on this hard, uneven substratum. We found that despite enforced protective measures, i.e., stopping fishing and collecting of marine life, banning fish feeding, and limiting the number of visitors, disturbance by human trampling on shallow sands still reduces the species richness in these areas. Cryptic biota below wading depths, and from adjacent coral rubble on sand, are not similarly affected. These results are similar to those from another heavily used beach on Oahu and cryptofauna ecology may be useful to adopt as a management option for Marine Preserves in other locations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bacterial profiling of White Plague Disease in a comparative coral species framework

Coral reefs are threatened throughout the world. A major factor contributing to their decline is outbreaks and propagation of coral diseases. Due to the complexity of coral-associated microbe communities, little is understood in terms of disease agents, hosts and vectors. It is known that compromised health in corals is correlated with shifts in bacterial assemblages colonizing coral mucus and tissue. However, general disease patterns remain, to a large extent, ambiguous as comparative studies over species, regions, or diseases are scarce. Here, we compare bacterial assemblages of samples from healthy (HH) colonies and such displaying signs of White Plague Disease (WPD) of two different coral species (Pavona duerdeni and Porites lutea) from the same reef in Koh Tao, Thailand, using 16S rRNA gene microarrays. In line with other studies, we found an increase of bacterial diversity in diseased (DD) corals, and a higher abundance of taxa from the families that include known coral pathogens (Alteromonadaceae, Rhodobacteraceae, Vibrionaceae). In our comparative framework analysis, we found differences in microbial assemblages between coral species and coral health states. Notably, patterns of bacterial community structures from HH and DD corals were maintained over species boundaries. Moreover, microbes that differentiated the two coral species did not overlap with microbes that were indicative of HH and DD corals. This suggests that while corals harbor distinct species-specific microbial assemblages, disease-specific bacterial abundance patterns exist that are maintained over coral species boundaries.     

Marine Polychaete Annelids of Easter Island

This study increases the number of species of marine polychaete annelids known to occur at Easter Island from 11 to 60, of which 43 are identified to species. Nearly 90% of these occur in the tropical Indo-West Pacific region, but 60% are of circumtropical distribution. The strong Indo-West Pacific zoogeographic affinity is consistent with other taxa of Easter Island inshore marine animals for which data are available, the fishes, corals, and gastropod molluscs. Polychaete species composition and abundance were determined in substrate samples from two types of microhabitat in a tidepool. A sample of 290 ml of sand and 70 ml of algae contained 1,779 specimens of 41 species of polychaetes (species diversity H′ = 2.57). A basalt boulder of surface area 340 cm² contained a polychaete assemblage of 864 specimens of 35 species (H′ = 2.49). Population density of the latter sample is equivalent to 25,400 polychaetes/m². Of the 49 species present in the two samples, 34 were identified to species. Although 27 species (55%) were common to both samples, similarity as measured by C_λ, which weighs differences in relative abundance, was only 24%. More than half of all polychaetes present in the two samples belonged to the family Syllidae; they comprised 65% of the individuals in the sand-algae sample and 35% in the boulder sample. Spirorbinae predominated numerically in the boulder sample (40%). Chaetopteridae (10%) and Spionidae (8%) were the next most abundant families in the sand-algae sample.     

Diversity and composition of macrobenthic community associated with sandy shoals of the Louisiana continental shelf

Along the Louisiana, USA continental shelf, sandy shoals are shallow, possibly oxygen-rich “islands” surrounded by deeper muddy deposits prone to hypoxia. Shoals also contain significant quantities of fine sand that may be mined in the future for coastal restoration. The ecological role of shoals remains poorly understood and we hypothesized that shoals provide critical habitat for benthic invertebrates. Using Ship Shoal as a model system, we assessed the diversity and structure of macrobenthic assemblages and how community structure varies with season and environmental parameters. High biomass (averaging 26.7 g m⁻²) and high diversity (161 species) of macrobenthos was found in 2006. Polychaetes (45%—72 species) and crustaceans comprised most of the species (28%—46 species); spionids and amphipods dominated the polychaete and crustacean groups respectively, both in terms of number of species and abundances. Sharp decreases in diversity, abundance and biomass occurred from spring to autumn. Species diversity and total abundance significantly increased with decreasing sediment grain size and increasing bottom water dissolved oxygen. Across seasons, mole crabs Albunea paretii and amphioxus Branchiostoma floridae typified the community and contributed most of the biomass. The polychaetes Nephtys simoni, Neanthes micromma, Dispio uncinata, Mediomastus californiensis and Magelona sp. A, the amphipod Acanthohautorius sp. A and the burrowing shrimp Ogyrides alphaerostris also contributed to variation in community composition. Cluster analyses quantified seasonal variation, mainly based on sharp decreases in abundance, as well as spatial differences in species composition oriented along both east–west and north–south gradients. Variation in benthic assemblages was correlated with water depth and sediment characteristics (mean grain size and percentage of gravel-sized shell debris). We conclude that Ship Shoal is an unrecognized biodiversity hotspot and a hypoxia refuge compared to the immediate surrounding area where the benthic community is affected by seasonal hypoxia events and we discuss how sand-mining may influence this community.     

Danian cold‐water corals from the Baunekule facies,Faxe Formation,Denmark: a rare taphonomic window of a coral mound flank habitat

Well‐preserved cold‐water corals are comparatively rare in the fossil record. This is partly due to the very low fossilization potential of the predominantly aragonitic corals but also due to the fact that coral ecosystems of deep water are a geologically young development. A Middle Danian cold‐water coral mound complex is well exposed in Faxe Quarry, Denmark. The coral mounds are intercalated with bryozoan mounds of various sizes and form the Faxe Formation. The coral limestone displays large variations in diagenesis, and this complicates the palaeoecological reconstructions. However, the Baunekule facies from the Faxe Formation contain a well‐preserved originally aragonitic and calcitic fauna. The aragonitic skeletons have been recrystallized to calcite during early diagenesis and the excellent preservation makes taxonomic identifications straightforward. A diverse fauna of ten scleractinian coral species, nine stylasterine coral species and seven octocoral species has been described from the Baunekule facies. The fossil fauna represents an ecological niche between the dead coral framework and coral rubble on a flank of a growing Dendrophyllia coral mound with multiple colonization events. The diversity and relative abundance of the fossil scleractinian corals are comparable to the modern settings in the NE Atlantic and Mediterranean. The distribution and diversity of the octocorals and the stylasterine corals are suggested to represent coral gardens as described from modern setting in the NE Pacific. The presence of a diverse and abundant stylasterine fauna suggests a stable palaeoenvironment, probably in a bathymetric depth range of 200–400 metre.     

Diversity,habitats and size-frequency distribution of the gastropod genus Conus at Dahab in the Gulf of Aqaba,Northern Red Sea

Topographically complex subtidal reefs of the Indo-West Pacific region are characterised by a high species richness of cone snails of the genus Conus (up to 36 on some reefs) but low population densities (≤1 individual/m²), whereas Conus assemblages on reef flats usually support fewer species (5–9) and high population densities (up to 5.2 individuals/m²). Subtidal sand areas are known to be least species-rich (1–6 species). Although the diversity of this predatory gastropod genus has been described previously from different areas of the Indo-Pacific, little ecological information is available on Conus in the Northern Red Sea. Therefore, data from five habitat types were obtained along 73 line-transects (245?m²⁾, which yielded ecological data for a total of 175 individuals of 9 species. In accordance with former findings, our results demonstrate that the reef flat was the habitat with the highest observed population densities (6.15 individuals/m²) but low species diversity (H’ = 0.9; 5 species); subtidal reefs, in contrast, were characterised by low densities (0.13 individuals/m²) and a relatively high species diversity (H ‘= 1.5; 6 species). This suggests that Conus diversity and species richness in the Northern Red Sea around Dahab is lower than in other parts of the Indo-West Pacific region. Furthermore, hardand soft substrata were dominated by different Conus species in accordance to the distribution of favourable microhabitat patches, the degree of physical stress and the availability of refuges and prey organisms. The fact that these Conus were predominantly small-bodied vermivores (size range: 6–85?mm; mean shell size: 15?mm; SD = 9?mm) suggests that this size class possesses an advantage over molluscivores and piscivores. Except for subtidal reefs, which showed a highly variable species composition, the studied habitat types around Dahab were characterised by distinct assemblages of Conus.     

Dinoflagellate-targeted PCR reveals highly abundant and diverse communities of parasitic dinoflagellates in and near Zhubi Reef,South China Sea

While diversity of symbiodiniacean dinoflagellates has been a focus of coral reef ecological research, information on the diversity of planktonic dinoflagellates in reef ecosystems remains limited. We used dinoflagellate-targeted PCR to investigate dinoflagellate diversity for a coral reef ecosystem. In the summer of 2007, plankton samples were collected from a lagoon, atoll, and open sea area of Zhubi Reef in the Nansha Islands, South China Sea. Sequencing of dinoflagellate-specific SSU rDNA clone libraries from samples in each of these habitats revealed high diversity and numerous novel dinoflagellate lineages. Gymnodiniales were most abundantly represented in all three water areas. Lagoon assemblages were co-dominated by Syndiniales and Gonyaulacales, the atoll by Gonyaulacales and Peridiniales, and the open sea by Syndiniales and Prorocentrales taxa. Species in the Syndiniales (group II) genus Amoebophrya were represented by eight new sequences and 13 previously described clades and were dominated by species reported to infect Gymnodiniales, Gonyaulacales, Peridiniales, and Prorocentrales taxa. And Amoebophrya were particularly abundant and diverse in the lagoon. Our results suggest that Amoebophrya probably play an important role in regulating dynamics of dinoflagellate assemblages in the Zhubi Reef coral ecosystem. In contrast, the few symbiodiniacean taxa detected occurred only in the open sea, suggesting planktonic aposymbiotic Symbiodiniaceae rarely occur in the reef ecosystem. We demonstrate the usefulness of a dinoflagellate-specific molecular technique for profiling dinoflagellate communities, and uncover diversity and the potential importance of parasitic lineages in a coral reef ecosystem.

     

Differences in microbial communities between healthy and bleached coral Acropora solitaryensis from Xisha Islands,South China Sea

Serious bleaching events have been observed in Acropora solitaryensis, one of the main species of reef-building coral in the area of the Xisha islands in the South China Sea, during 2008–2011. The microbial communities of healthy and bleached coral samples were compared to explore the difference in the bacterial composition using 16S rRNA gene sequencing and denaturing gradient gel electrophoresis (DGGE). Analysis of 16S rRNA gene sequences showed that the diversity of bacteria from the corals was different between the healthy and the bleached. Albeit both the healthy coral and bleached coral displayed similar dominant bacterial species (α- and γ-proteobacteria), the ratio of Vibrio spp. increased sharply in the latter. As the bleaching developed, the diversity of the microbial community was dramatically decreased and the dominant species were replaced by γ-proteobacteria where Vibrio spp. and Escherichia spp. overwhelmed other genera. Similar results were gained by the DGGE technique though the abundance was lower. Furthermore, in the bleached tissues, Vibrio coralliilyticus was identified using both methods. These results indicated that pathogenic Vibrio spp. might be one of the factors causing A. solitaryensis bleaching in the coral reef of the Xisha islands.