Coral Ecosystems Research Articles

Composition of the zooplankton community associated with mesophotic corals in “Corales de Profundidad” National Natural Park, Colombian Caribbean

Mesophotic coral ecosystems (MCE) are located between 30 and 150 m deep and shelter unique communities. However, they have been poorly studied due to the high cost of the available sampling technologies. Zooplankton are key organisms for the maintenance of the coral colonies as their primary food source because the zooxanthellae in these habitats have a low photosynthetic rate due to the low light incidence. The purpose of this work was to characterize the zooplankton community associated with MCEs. We took 15 samples (three samples per station) by filtering 24 L of seawater (45 µm mesh size) in five stations at Bajo Fríjol with a device designed to collect zooplankton right just above the reef substrate. We determined the taxonomic composition, density, and relative abundance, and we categorized the species according to their trophic level. Crustaceans (especially nauplii and copepods), tintinnids, and foraminifers were the most abundant while tintinnids and radiolarians had the higher species richness. Herbivores dominated in both composition and abundance as usually happens in other pelagic communities. We present here the first reports of planktonic radiolarians and tintinnids from oceanic zones and MCEs in the Colombian Caribbean and the first global list of zooplankton species associated with MCEs.

Persistence of marine heat waves for coral bleaching and their spectral characteristics around Andaman coral reef.

Coral reefs are fragile and endangered ecosystems in the tropical marine and coastal environment. Thermal stress due to marine heat waves (MHW) could cause significantly negative impacts on the health conditions, i.e., bleaching of the coral ecosystem. The current study is an attempt to quantify the intensity of coral bleaching in the Andaman region in recent decades using the intensity of marine heat wave (IMHW) estimated from satellite measured sea surface temperature (SST). A linear regression model was developed between IMHW and in situ observations of percent coral bleaching (PCB) which has the slope 7.767 (of IMHW unit) and intercept (- 141.7). Further, an attempt was also made to establish the relationship between PCB and the ratio between the remote sensing reflectance (Rrs) at 443 and 531nm to upscale the percentage of coral bleaching at synoptic scales. A significant positive correlation between the PCB and band ratio index was found (R2 = 0.72). This approach can be used for the operational monitoring of coral reef beaching in this region.

Caulerpa Bikinensis (Chlorophyta) Preference for the Mesophotic Depths of Pacific Atolls1

The marine green alga Caulerpa bikinensis W. R. Taylor was described as a new species in 1950 from dredged specimens (37–57 m depth) from Bikini Atoll and Rongelap Atoll in the Marshall Islands. Its relative rareness in collections from waters less than 30 m deep from these atolls indicated that it favored the mesophotic coral ecosystem (MCE) at depths of 30–150 m. Published and unpublished records of this species over the past 70 years show its habitat preference on the seaward slopes of atolls and in lagoons. Observations were based on collections from Pacific atolls of the Marshall Islands, Tuamotu Islands, Chuuk State in the Federated States of Micronesia, Cook Islands, and Johnston Atoll, and on the deep lagoonal reefs of Palau. Caulerpa bikinensis has also been recorded in shallow waters 1 m deep in dark microcavities on lagoonal pinnacles at Takapoto Atoll (Tuamotu Islands) and in Chuuk Lagoon, and 2 m deep at Raroia Atoll (Tuamotu Islands). Caulerpa bikinensis favors the deeper depths of the MCE for its low light intensity rather than its cooler temperature, and definitely shows a strong affinity to the high energy seaward slopes of calcareous Pacific atolls.

A Review of Marine Viruses in Coral Ecosystem

Coral reefs are among the most biodiverse biological systems on earth. Corals are classified as marine invertebrates and filter the surrounding food and other particles in seawater, including pathogens such as viruses. Viruses act as both pathogen and symbiont for metazoans. Marine viruses that are abundant in the ocean are mostly single-, double stranded DNA and single-, double stranded RNA viruses. These discoveries were made via advanced identification methods which have detected their presence in coral reef ecosystems including PCR analyses, metagenomic analyses, transcriptomic analyses and electron microscopy. This review discusses the discovery of viruses in the marine environment and their hosts, viral diversity in corals, presence of virus in corallivorous fish communities in reef ecosystems, detection methods, and occurrence of marine viral communities in marine sponges.

Seasonal fluctuations in symbiotic bacteria and their role in environmental adaptation of the scleractinian coral Acropora pruinosa in high-latitude coral reef area of the South China Sea

Coral-associated bacterial communities are paramount for coral ecosystems and holobiont health. However, the role of symbiotic bacteria in the adaptation of high-latitude corals to seasonal fluctuations remains underexplored. Therefore, we used 16S rRNA-based high-throughput sequencing to analyze the symbiotic bacterial diversity, composition, and core bacterial community in high-latitude coral and explored the seasonal fluctuation characteristics of symbiotic bacterial communities. We found that bacterial richness and α-diversity changed significantly across different seasons. Additionally, the community structure recombined seasonally, with different dominant bacterial phyla and genera in different seasons. However, the symbiotic bacterial community structures of Acropora pruinosa in winter and spring were similar. Proteobacteria were the dominant bacteria in spring, autumn, and winter. In summer, the dominant bacterial taxa were Bacteroidota and Proteobacteria. Ralstonia was the dominant bacterial genus in spring and winter, whereas in autumn, BD1-7_clade was dominant. Linear discriminant analysis effect size identified 20 abundant genera between the different groups. Core microbiome analysis revealed that 12 core bacterial operational taxonomic units were associated with A. pruinosa in all seasons, seven of which varied with the seasons, changing between dominant and rare. Distance-based redundancy and variation partitioning analyses revealed that sea surface temperature was the major contributor of variation in the microbial community structure. We hypothesized that the high diversity and abundance of symbiotic bacteria and the increase in Prosthecochloris abundance in coral in summer can help A. pruinosa maintain its physiological functions, ameliorating the negative physiological effects of the decrease in Symbiodiniaceae density under high-temperature stress. Thus, the rapid reorganization of the symbiotic bacterial community structure and core microflora in different seasons may allow the corals to adapt to large seasonal environmental fluctuations. In conclusion, seasonal variation of bacteria plays an important role in coral adaptation to large environmental fluctuations.

Global coral reef ecosystems exhibit declining calcification and increasing primary productivity

Long-term coral reef resilience to multiple stressors depends on their ability to maintain positive calcification rates. Estimates of coral ecosystem calcification and organic productivity provide insight into the environmental drivers and temporal changes in reef condition. Here, we analyse global spatiotemporal trends and drivers of coral reef calcification using a meta-analysis of ecosystem-scale case studies. A linear mixed effects regression model was used to test whether ecosystem-scale calcification is related to seasonality, methodology, calcifier cover, year, depth, wave action, latitude, duration of data collection, coral reef state, Ωar, temperature and organic productivity. Global ecosystem calcification estimated from changes in seawater carbonate chemistry was driven primarily by depth and benthic calcifier cover. Current and future declines in coral cover will significantly affect the global reef carbonate budget, even before considering the effects of sub-lethal stressors on calcification rates. Repeatedly studied reefs exhibited declining calcification of 4.3 ± 1.9% per year (x̄ = 1.8 ± 0.7 mmol m−2 d−1 yr−1), and increasing organic productivity at 3.0 ± 0.8 mmol m−2 d−1 per year since 1970. Therefore, coral reef ecosystems are experiencing a shift in their essential metabolic processes of calcification and photosynthesis, and could become net dissolving worldwide around 2054.

Climate-induced species range shift and local adaptation strategies in a temperate marine protected area, Ashizuri-Uwakai National Park, Shikoku Island, western Japan

In temperate seas, expansion of reef-building coral distribution, decline of macroalgal beds, and changes in constituent species for coral communities and/or macroalgal beds mainly due to increase in sea surface temperature have been reported. Not only mitigation but also adaptive responses are important for the measures against climate change. Consideration of adaptive measures depends on local conditions such as the degree of environmental change and industrial structure is necessary when measures are implemented. This study focused on the marine protected area (Ashizuri-Uwakai National Park in Japan) and its surrounding area. This area is characterized by a very large north-south gradient in water temperature and the distribution of corals and macroalgae along it. The purpose of this study is to consider what adaptive measures are suitable for each region and industry in response to changes in coastal ecosystems (coral community and macroalgal bed). Future (assuming the end of this century under RCP2.6 and RCP8.5 scenarios) changes in the potential distribution area of coral, macroalgae, and their consumers were projected using simulated sea surface temperature with a high-spatial resolution. After projecting the coastal ecosystem changes and assessing the contemporary use of coastal ecosystem, we give examples of what specific adaptive measures should be taken in each area for three fields, i.e., biodiversity conservation, fisheries, and tourism. Assuming the 2090s, though drastic changes in coastal ecosystem are not projected compared to the present state under RCP2.6 scenario, as coral distribution shifts north, feeding damage by crown-of-thorn starfish is projected to become a problem. Therefore, expansion of protected areas and promotion of conservation activities are major challenges for coral ecosystem conservation. On the other hand, under RCP8.5 scenario, it is important to take appropriate conservation measures for macroalgae since coral growth becomes difficult to achieve and grazing pressure on macroalgae increases due to extreme elevated water temperature. Moreover, creation of alternate or new tourism resources will be needed. This research represents projected scenarios of coastal ecosystem changes with a high spatial resolution and adaptation measures based on the changes for each municipality.

Characterizing Geomorphology of Mesophotic Coral Reef Ecosystems in the Southwestern Gulf of Mexico: Implications for Conservation and Management

Coral reefs are the most biodiverse ecosystems on earth and are presently experiencing severe declines globally. Shallow coral reef ecosystems (<30 m) have been studied extensively while mesophotic coral ecosystems (MCE) are poorly studied. As a result, MCE are rarely included in marine reserve design and management, despite their ecological importance and connectivity to shallow reefs. In this study, we assessed the fine-scale topographic complexity, a proxy for structural complexity, for a group of coastal coral reefs in a marine park in the southwestern Gulf of Mexico, in depths between 2 and 49 m. We conducted hydrographic surveys using a semi-portable multibeam echosounder system to produce 3D bathymetry digital terrain models (DTM) with a 2.5 m spatial resolution for three submerged bank reefs and two emerging reefs. From these models, descriptive terrain parameters were calculated for each reef, including slope, aspect, curvature, rugosity and ruggedness. Results show that all reefs are predominantly northeast-southwest oriented, with well-defined leeward and windward sides. For the three submerged bank reefs, structural complexity increased with depth. Estimated mean ruggedness and rugosity were highest at 20–40 m depth range on windward side slopes. Emerging reefs showed high structural complexity, particularly at the 25–40 m depth range. We identified a spur and groove zone with maximum ruggedness (0.26) and rugosity (3.17) values, and four channels with steep slopes (68°) and dispersed mounds. We found that at mesophotic depths (>30 m), southern reefs basements from two distinct reefs merge to form a continuous complex. This has important management implications since presently, only 28.7% of this reef complex (mostly shallow areas) are within the existing limits of the marine park’s core zone. Considering the newly recognized importance of MCE, we propose expanding and reshaping the core zone to include the entire reef complex which mostly encompasses MCE with high structural complexity. Our study illustrates the value of semi-portable MBES for marine planning in developing countries and remote poorly studied areas.

STRATEGI PENGELOLAAN EKOSISTEM TERUMBU KARANG DI DAERAH WISATA AIR TANJUNG BENOA DAN JEMELUK AMED, BALI

Tanjung Benoa and Jemeluk Amed are two famous marine tourism sites in Bali. This study aims to determine the state of coral ecosystem in its life form, factors associated with coral damage, and the strategy to manage coral in those two area. We used two methods: Line Intercept Transect (LIT) and SWOT. The live coral coverage condition in Tanjung Benoa is in moderate and worse category. While the Jemeluk Amed is in moderate level and good condition, respectively. Factors causing damage to coral ecosystem are: the corals are under pressure, some corals are already bleaching, the anchoring activity and oil spill from ships, and algae. The coral reefs ecosystem in Tanjung Benoa and Jemeluk Amed can be sustained in good condition with government support and NGOs in the development of environmentally friendly activities and monitoring studies, implementation of coral reef preservation rules (prohibition of taking coral reefs) and colaboration of the community, government, and NGOs to carry out coral reef rehabilitation and monitoring studies. As one of the tourism area in Bali, the role of universities are needed for continuous research on the state of coral reefs to maintain environmentally friendly and sustainable tourism.Keywords: Coral reef; Life form; Strategy; Marine conservation.

New Distributional Record of Twelve Scleractinian Corals From Saint Martin’s Island, Bangladesh

Saint Martin's Island is the only island in Bangladesh where coral communities are found. An expedition on marine biodiversity monitoring of Saint Martin’s Island through underwater visual census method was carried out from December 2017 to March 2018. In this study, a total of 25 scleractinian coral species of 8 families and 14 genera were identified, of which 12 species, Dipsastraea lizardensis, Dipsastraea maritima, Dipsastraea veroni, Favites acuticollis, Favites melicerum, Favites pentagona, Goniastrea stelligera, Goniopora albiconus, Goniopora norfolkensis, Pavona clavus, Plesiastrea versipora, and Psammocora exesa were recorded for the first time in Bangladeshi marine water. These new records exemplify gaps in sampling and recording of coral species in Bangladesh, and suggest the need of extensive research on coral ecosystem in the country. Assessment of different valid reports and publications including the present study revealed that a total of 98 species of hard corals of 18 families and 37 genera have been reported until now in Saint Martin’s Island as well as Bangladesh. Bangladesh J. Zool. 49(1): 03-18, 2021

The Significance of Genotypic Diversity in Coral Competitive Interaction: A Transcriptomic Perspective

Competitive interactions shape coral assemblages and govern the dynamics of coral ecosystems. Although competition is an ecological concept, the outcomes of competitive interactions are ultimately determined by patterns of gene expression. These patterns are subject to genotypic variation on both sides of any interaction. Such variation is typically treated as “noise”, but it is sometimes possible to identify patterns within it that reveal important hidden factors in an experiment. To incorporate genotypic variation into the investigation of coral competitive interactions, we used RNA-sequencing to study changes in gene expression in a hard coral (Porites cylindrica) resulting from non-contact competition experiment with a soft coral (Lobophytum pauciflorum). Hard coral genotype explained the largest proportion of variation between samples; however, it was also possible to detect gene expression changes in 76 transcripts resulting from interaction with the soft coral. In addition, we found a group of 20 short secreted proteins that were expressed as a coordinated unit in three interacting Porites-Lobophytum pairs. The presence of this secretion response was idiosyncratic in that it could not be predicted based on polyp behaviour, or the genotype of hard or soft coral alone. This study illustrates the significance of individual variation as a determinant of competitive behaviour, and also provides some intriguing glimpses into the molecular mechanisms employed by hard corals competing at a distance.

Estimation of the CO2 flux index in the San Andrés Island using fuzzy logic

When applying diffuse inference systems through the GeoFIS tool in a database of the coral complex of the island of San Andrés, a CO2 flux index was estimated that allows us to know the effect of the flux on the sea and the influence of the variables involved. It was found that six of the studied areas had a state of acidification of the sea due to CO2, while all the other areas had a slight incorporation of the gas. Likewise, it was evident that the variables that have a significant influence on the incorporation of CO2 into the marine environment are the sea surface temperature and the chemical nature of this gas, according to the component analysis. Therefore, the diffuse methods for the determination of acidification of coral ecosystems, allows establishing an approach to the effects that the gradual incorporation of CO2 would have into the marine environment, in addition to providing excellent advantages in terms of its determination based on satellite information.

Microplastic pollution in Marine Protected Areas of Southern Sri Lanka

Microplastics (MPs) are ubiquitous in marine environment. The prevalence of MPs in coastal and lagoon sediments, and water were studied in two Marine Protected Areas (MPAs); Bundala National Park (BNP) and Hikkaduwa Marine National Park (HNP) in Sri Lanka. Both areas are important for turtles, birds and coral ecosystems, all of which are particularly threatened by MPs. Abundance of MPs was generally higher in both coastal sediments and waters in HNP (111±29 MPs/m2 for sediments and 0.515±0.054 MPs/m3 for water) than in the BNP (102±16 MPs/m2 for sediments and 0.276±0.077 MPs/m3 for water). The most common shape and polymer type of MPs were fragments and Polyethylene respectively. This research is the first to survey MPs in MPAs in Sri Lanka and provides a baseline of MPs pollution in these environments for future research and management.

First approach to the characterization of the ecological succession on perforated trapezoidal multi-purpose reef modules: Building climate resilience

The study reports the colonization and ecological succession of epibenthic communities on perforated trapezoidal Artificial Reef (AR) modules deployed in Vaan Island of Gulf of Mannar, southeast India. These AR communities assist in building climate resilience among the coastal ecosystems, which have faced severe climate change impacts during the last decade. Based on wave dynamics modeling studies, 10,600 modules were deployed in two layers to protect the Island from beach erosion and to enhance biodiversity. Randomly selected modules were subject to continuous monitoring from 2015 to 2020 to understand the ecological succession of the epibenthic communities. Hard corals turned out to be the dominant epibenthic category with 76.01 no.module−1(SE ± 2.16) by 2020. A total of 37 coral species belonging to 16 genera were found inhabiting the modules at the end of five years. The other major epibenthic categories were molluscs, hydroids, sponges, ascidians, octocorals and echinoderms with a total density of 40.44 no.module−1(SE ± 1.41) by 2020. A couple of years after the deployment, when hard corals started to flourish on the AR modules, the density of other epibenthic categories began to decline. A comparison of the numbers of epibenthic organisms on the inner and outer layers of AR modules reveals that the inner layer has a larger epibenthic community. After five years, the AR modules have started to act as coral refugia and are expected to create reef ecosystem analogous to natural reefs. The modules also provide the much needed topographic complexity for the fish to move in. This planned deployment not only helped in reef recovery and enhancement of associated biodiversity in Gulf of Mannar, which is severely impacted by global climate change, but also would serve to enhance the climate resilience of the coral ecosystems by increasing the coral biomass and thereby restoring the ecological services, which help to sustain the livelihood of the dependent small-scale fisher folk.

Upper-mesophotic and shallow reef corals exhibit similar thermal tolerance, sensitivity and optima

The physiology of ectotherms living in marine environments is strongly influenced by their local thermal experience. Scleractinian corals living near their thermal optimums are increasingly vulnerable to bleaching and mortality as oceanic heat waves increase globally. Mesophotic coral ecosystems (MCEs) below 30 m depths are characteristically cooler than adjacent shallow water reefs, which according to theory should result in differential metabolic responses to temperature between depths. How local temperatures influence physiological responses in mesophotic corals is poorly understood. We compared thermal sensitivities of four coral species between a shallow (5–10 m) and upper-mesophotic (30−35 m) reef in Bermuda. Thermal performance curves (TPC) were measured in laboratory mesocosms for four common coral species (Diploria labyrinthiformis, Orbicella franksi, Montastraea cavernosa and Porites astreoides) across a wide range of temperatures (19−36). Our results indicate that the maximum rate of gross photosynthetic (GP) performance (GP-Pmax) and the mean overall photosynthetic rates (GP-lnc) varied significantly among species. In contrast, thermal sensitivity (Pmax, Topt, lnc, E, Eh, or Th) did not vary between depths for conspecifics except for deactivation energy (GP-Eh) in D. labyrinthiformis. Additionally, gross respiration (R) did not differ among species or between depths for any thermal metric. Similar metabolic responses between depths suggest that local adaptation and/or acclimatization to different thermal conditions is likely not occurring. Instead, upper-mesophotic corals in Bermuda do not have lower bleaching thresholds than shallow water conspecifics, but similar thermal sensitivities supporting the potential for MCEs to function as a thermal refuge.

Coral associated bryozoans and their role in reviving the depleting coral ecosystem

Coral reefs are one of the important habitats of marine biodiversity in shallow tropical waters as they sustain numerous crucial ecosystem services. This study provides the taxonomic account and sheds light on the habitat of Bryozoan species, which exclusively considers corals as its substratum for their growth and their role in reviving the depleting coral ecosystem. The systematic description of 12 coral associated bryozoans is, discussed here. Among the described 12 species, six of them, Parasmittina collifera (Robertson, 1908), Smittipora philippinensis (Canu and Bassler, 1929), Onychocella angulosa (Reuss, 1848), Plesiocleidochasma porcellanum (Busk, 1860), Robertsonidra argentea (Hincks, 1881) and Schizoporella errata (Waters, 1878) are reported for the first time in Indian waters. The survey was conducted during April 2013–April 2015 in Gulf of Mannar Marine Biosphere Reserve (GoMBR). Bryozoan species were, collected from the coral rubble and coral skeletal framework in the shallow waters (up to 5 m) and illustrated by scanning electron microscopy (SEM). A conclusion was drawn from this study, where Bryozoans, which colonise dead coral skeletal framework and rubble, can revive the depleting coral reef ecosystem as they play a major role in cementation and act as pioneer species in succession.

Genetic Divergence and Polyphyly in the Octocoral Genus Swiftia [Cnidaria: Octocorallia], Including a Species Impacted by the DWH Oil Spill

Mesophotic coral ecosystems (MCEs) are recognized around the world as diverse and ecologically important habitats. In the northern Gulf of Mexico (GoMx), MCEs are rocky reefs with abundant black corals and octocorals, including the species Swiftia exserta. Surveys following the Deepwater Horizon (DWH) oil spill in 2010 revealed significant injury to these and other species, the restoration of which requires an in-depth understanding of the biology, ecology, and genetic diversity of each species. To support a larger population connectivity study of impacted octocorals in the GoMx, this study combined sequences of mtMutS and nuclear 28S rDNA to confirm the identity of Swiftia sea fans in the GoMx, compare these markers for different polyp colors in the GoMx and Atlantic, and examine the phylogeny of the genus. Two mtMutS haplotypes were identified, one seemingly endemic to the northern GoMx. Compared to other North Atlantic Swiftia, S. exserta, the type of the genus was found to be extremely divergent and distinct from the two other Swiftia at both loci, with strong evidence of polyphyly in the genus. This information refines our understanding of the geographical distribution of injured coral and highlights how little is known about MCEs. Substantial taxonomic revisions may be needed for several taxa injured by the DWH oil spill.

Photosynthesis and Bio-Optical Properties of Fluorescent Mesophotic Corals

Mesophotic coral ecosystems (MCEs) are light-dependent coral-associated communities found at 30–150 m depth. Corals inhabiting these deeper reefs are often acclimatized to a limited and blue-shifted light environment, enabling them to maintain the relationship with their photosynthetic algal symbionts (family Symbiodiniaceae) despite the seemingly suboptimal light conditions. Among others, fluorescent proteins produced by the coral host may play a role in the modulation of the quality and spectral distribution of irradiance within the coral tissue through wavelength transformation. Here we examined the bio-optical properties and photosynthetic performances of different fluorescence morphs of two mesophotic coral species Goniopora minor and Alveopora ocellata, in order to test the photosynthesis enhancement hypothesis proposed for coral fluorescence. The green morph of G. minor and the low fluorescence morph of A. ocellata exhibit, in their natural habitats, higher abundance. The morphs also presented different spectral reflectance and light attenuation within the tissue. Nevertheless, chlorophyll a fluorescence-based, and O2 evolution measurements, revealed only minor differences between the photosynthetic abilities of three fluorescence morphs of the coral G. minor and two fluorescence morphs of A. ocellata. The fluorescence morphs did not differ in their algal densities or chlorophyll concentrations and all corals harbored Symbiodiniaceae from the genus Cladocopium. Thus, despite the change in the internal light quantity and quality that corals and their symbionts experience, we found no evidence for the facilitation or enhancement of photosynthesis by wavelength transformation.

Richness, abundance and spatial heterogeneity of gastropods and bivalves in coral ecosystems across the Mexican Tropical Pacific

ABSTRACT The diversity of gastropods and bivalves, total mollusc richness and total mollusc abundance were analysed for three substrates (coral, rock and sand) in the coral and reef ecosystems of the Mexican Tropical Pacific (MTP). Up to 3,828 individuals (70% gastropods and 30% bivalves), belonging to 209 species (146 gastropods and 63 bivalves), were identified; this is one of the most diverse molluscan faunas (2.77 species/m2) associated with reef systems in the MTP. Evaluation of the sampling effort demonstrated that 80% of gastropod species and 93% of bivalve species inhabiting the reef system were recovered. The highest abundance occurred in the coral substrate (1,939 individuals), while the highest species richness was found on the rock substrate (131 species). The analysis showed that the greatest spatial variation in total mollusc, gastropod and bivalve diversity occurred among different substrates within individual localities, with minor differences among assemblages with increasing spatial scale reflecting the relative homogeneity of the molluscan fauna in the study area. While the gastropods Conus nux, Steironepion piperatum and Muricopsis zeteki accounted for differences among different regions, and Vermicularia pellucida eburnea and Bostrycapulus aculeatus accounted for differences among states, the abundances of M. zeteki, B. aculeatus and V. pellucida eburnea were related to differences in diversity at the scale of individual localities. Among bivalves, Leiosolenus aristatus, L. plumula and Gastrochaena ovata accounted for differences between regions, states and localities, respectively. Overall, the study shows that species composition is influenced by both the substrate and the geographical location of assemblages. This indicates that conservation strategies should address preserving habitat heterogeneity at local scales in the study area.

Gorgonians Are Foundation Species on Sponge-Dominated Mesophotic Coral Reefs in the Caribbean

Foundation species (FS) regulate ecological processes within communities often facilitating biodiversity and habitat complexity. Typically FS are dominant structure-forming taxa; but less dominant taxa having disproportionate ecological impacts to the community can also be FS. Mesophotic coral ecosystems (MCEs) are deep coral reef (∼30–150 m) communities, often dominated by emergent sponges in the Caribbean Basin. Despite the potential competitive advantage of sponges on MCEs, gorgonians are also common constituents of these reefs. Data from the Bahamas demonstrate increased biodiversity and densities of sponges on mesophotic reefs with gorgonians relative to reefs without these species. Drawing upon fifteen years of field surveys at five sites in the Caribbean Basin we assessed in situ interactions between gorgonians and sponges to quantify outcomes consistent with competition (i.e., tissue necrosis and overgrowth). Gorgonians were effective competitors against a variety of sponges, and two allelochemicals produced by Ellisella elongata were mechanistically important in interactions with Agelas clathrodes. We also examined invertebrate recruitment patterns near gorgonians to assess their role in facilitating MCE biodiversity. Our results indicate that live gorgonians, Antillogorgia bipinnata and E. elongata, facilitate biodiverse recruitment into MCEs, indicating that this process is governed by more than passive hydrodynamics. Collectively, these data indicate that these gorgonians exhibit both positive and negative ecological interactions (i.e., facilitation and competition, respectively) with sponges, and other taxa. Thus, these gorgonians are FS of MCE communities within the Caribbean Basin that display several traits contributing to the ecological structure of these understudied communities.