Assessing population structure of Diadema antillarum in a shallow reef of the southeastern coast of the Dominican Republic

The sea urchin Diadema antillarum is an herbivore that plays an important ecological role in controlling benthic community structure in Caribbean reefs. After the mass mortality documented between 1982-1983, their populations were reduced by 94-99% triggering a phase shift from coral to macroalgae-dominated benthic communities across the Caribbean. Almost 4 decades after its regional collapse, it is not clear weather D. antillarum populations are recovering, thus local surveys are valuable to track the fate of this herbivore. This study aims to determine the population structure of this sea urchin in a shallow reef located southeast of the Dominican Republic. We conducted a visual survey in three haphazardly selected sites of the reef studying a total surface of 90 m2 in which test size and D. antillarum densities were measured. Overall, the mean density of D. antillarum was 1.77 ± 1.07 ind/ m2 (Mean ± SD) with an average test size of 67.3 ± 22.7 mm (Mean ± SD) a median of 70 mm and a mode of 80 mm. Test diameter had a platykurtic distribution (kurtosis = 2.53) slightly skewed to the left (skewness = -0.1). This information is valuable to establish a local baseline to follow up the population dynamics of this key species.El erizo Diadema antillarum es un herbívoro clave en el control de las comunidades bentónicas del Caribe. Tras los eventos de mortalidad masiva de 1982-1983, sus poblaciones se redujeron un 94-99%, lo que provocó un cambio de fase de corales a comunidades dominadas por macroalgas en el Caribe. Casi 4 décadas después del colapso, esta especie no se está recuperando, por lo que los estudios locales son valiosos para conocer la tendencia de sus poblaciones. Nuestro objetivo es determinar su estructura poblacional en un arrecife poco profundo del sureste de la República Dominicana. Muestreamos en tres sitios del arrecife, explorando una superficie total de 90 m2 en los que se midieron el diámetro del caparazón y las densidades de D. antillarum. La densidad media de D. antillarum fue 1,77 ± 1,07 ind/ m2 (Media ± DE) con un tamaño de caparazón medio de 6,73 ± 2,27 cm (Media ± DE), una mediana de 7 cm y una moda de 8 cm. La distribución del diámetro fue platicúrtica (curtosis = 2,53), ligeramente sesgada hacia la izquierda (asimetría = -0,1). Estos resultados sirven para establecer una línea base para el seguimiento de la dinámica poblacional de esta especie

Site Selection for Coral Reef Restoration Using Airborne Imaging Spectroscopy

Over the past decade, coral restoration efforts have increased as reefs continue to decline at unprecedented rates. Identifying suitable coral outplanting locations to maximize coral survival continues to be one of the biggest challenges for restoration practitioners. Here, we demonstrate methods of using derivatives from imaging spectroscopy from the Global Airborne Observatory (GAO) to identify suitable coral outplant sites and report on the survival rates of restored coral at those sites. Outplant sites for a community-based, citizen science outplant event in Bávaro, Dominican Republic, were identified using expert-defined criteria applied to a suitability model from data layers derived from airborne imagery. Photo quadrat analysis of the benthic community confirmed the accuracy of airborne remote sensing maps with live coral cover averaging 3.5–4% and mean algal cover (macro algae and turf) ranging from 28 to 32%. Coral outplant sites were selected at 3–7 m depth with maximized levels of habitat complexity (i.e., rugosity) and live coral cover and minimized levels of macroalgal cover, as predicted by the imaging spectrometer data. In November 2019, 1,722 Acropora cervicornis fragments (80–180 mm in length) were outplanted to these sites. Surveys conducted in January 2020 in four of these sites confirmed that 92% of outplants survived after 3 months. By October 2020 (11 months after outplanting), survivorship remained above 76%. These results demonstrate higher than average success rates for coral outplant survival for this species. An online tool was developed to enable replication and facilitate future selection of coral restoration sites. Our objective is to present a case study that uses GAO-derived map products within a suitability model framework to provide a quantitative and replicable method for selecting coral restoration sites with the goal of increasing outplant survival over time

Stony Coral Tissue Loss Disease and Other Diseases Affect Adults and Recruits of Major Reef Builders at Different Spatial Scales in the Dominican Republic

Monitoring programs can help understand coral disease dynamics. Here, we present results from a national program in the Dominican Republic (DR) aimed at evaluating coral diseases 3 times a year following a nested spatial design. Prevalence of coral diseases in DR varied from sites to regions, suggesting that disease dynamics can be driven by local processes and/or across larger spatial scales. Three diseases were common: Dark Spot (DSD), Yellow Band (YBD) and Stony Coral Tissue Loss Disease (SCTLD). DSD and YBD were more prevalent across the western coast (north and south), whereas SCTLD was restricted for the study period to the northern coast. SCTLD has become endemic in the northwestern coast, epizootic in the northeastern, and absent in other sites across DR. SCTLD prevalence in the northwest was below 10% across sites, whereas in the northeast it varied from 2.13±3.69% (mean± sd) to 38.7±13.55% in Galeras and from 1.9±0.99% to 38.5±19.8% in Samaná. Over 10 coral species were affected by SCTLD in DR, with Pseudodiploria spp, Dendrogyra cylindrus, Eusmilia fastigiata, Siderastrea siderea, Montastraea cavernosa and Meandrina spp, being the most susceptible. We observed SCTLD affecting recruits and juvenile corals with 5% prevalence on average. Furthermore, we observed Oreaster reticulatus climbing on 1% healthy and 27% SCTLD P. strigosa colonies in Samaná. We conclude that SCTLD is a serious problem in DR, producing rapid loss of coral cover of major reef builders that are locally used for propagation efforts. This monitoring plan will provide future insights to design more effective disease responses

Characterisation of the bacterial and fungal communities associated with different lesion sizes of Dark Spot Syndrome occurring in the Coral Stephanocoenia intersepta

The number and prevalence of coral diseases/syndromes are increasing worldwide. Dark Spot Syndrome (DSS) afflicts numerous coral species and is widespread throughout the Caribbean, yet there are no known causal agents. In this study we aimed to characterise the microbial communities (bacteria and fungi) associated with DSS lesions affecting the coral Stephanocoenia intersepta using nonculture molecular techniques. Bacterial diversity of healthy tissues (H), those in advance of the lesion interface (apparently healthy AH), and three sizes of disease lesions (small, medium, and large) varied significantly (ANOSIM R = 0.052 p,0.001), apart from the medium and large lesions, which were similar in their community profile. Four bacteria fitted into the pattern expected from potential pathogens; namely absent from H, increasing in abundance within AH, and dominant in the lesions themselves. These included ribotypes related to Corynebacterium (KC190237), Acinetobacter (KC190251), Parvularculaceae (KC19027), and Oscillatoria (KC190271). Furthermore, two Vibrio species, a genus including many proposed coral pathogens, dominated the disease lesion and were absent from H and AH tissues, making them candidates as potential pathogens for DSS. In contrast, other members of bacteria from the same genus, such as V. harveyii were present throughout all sample types, supporting previous studies where potential coral pathogens exist in healthy tissues. Fungal diversity varied significantly as well, however the main difference between diseased and healthy tissues was the dominance of one ribotype, closely related to the plant pathogen, Rhytisma acerinum, a known causal agent of tar spot on tree leaves. As the corals’ symbiotic algae have been shown to turn to a darker pigmented state in DSS (giving rise to the syndromes name), the two most likely pathogens are R. acerinum and the bacterium Oscillatoria, which has been identified as the causal agent of the colouration in Black Band Disease, another widespread coral disease

Development of Bacterial Biofilms on Artificial Corals in Comparison to Surface-Associated Microbes of Hard Corals

Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in their surrounding environment. However, these environmental samples often represent vastly different microbial micro-environments with few studies having looked at the settlement and growth of bacteria on surfaces similar to corals. As a result, it is difficult to determine which bacteria are associated specifically with coral tissue surfaces. In this study, early stages of passive settlement from the water column to artificial coral surfaces (formation of a biofilm) were assessed. Changes in bacterial diversity (16S rRNA gene), were studied on artificially created resin nubbins that were modelled from the skeleton of the reef building coral Acropora muricata. These models were dip-coated in sterile agar, mounted in situ on the reef and followed over time to monitor bacterial community succession. The bacterial community forming the biofilms remained significantly different (R = 0.864 p<0.05) from that of the water column and from the surface mucus layer (SML) of the coral at all times from 30 min to 96 h. The water column was dominated by members of the α-proteobacteria, the developed community on the biofilms dominated by γ-proteobacteria, whereas that within the SML was composed of a more diverse array of groups. Bacterial communities present within the SML do not appear to arise from passive settlement from the water column, but instead appear to have become established through a selection process. This selection process was shown to be dependent on some aspects of the physico-chemical structure of the settlement surface, since agar-coated slides showed distinct communities to coral-shaped surfaces. However, no significant differences were found between different surface coatings, including plain agar and agar enhanced with coral mucus exudates. Therefore future work should consider physico-chemical surface properties as factors governing change in microbial diversity

Tissue mortality by Caribbean ciliate infection and white band disease in three reef-building coral species

Caribbean ciliate infection (CCI) and white band disease (WBD) are diseases that affect a multitude of coral hosts and are associated with rapid rates of tissue losses, thus contributing to declining coral cover in Caribbean reefs. In this study we compared tissue mortality rates associated to CCI in three species of corals with different growth forms: Orbicella faveolata (massive-boulder), O. annularis (massive-columnar) and Acropora cervicornis (branching). We also compared mortality rates in colonies of A. cervicornis bearing WBD and CCI. The study was conducted at two locations in Los Roques Archipelago National Park between April 2012 and March 2013. In A. cervicornis, the rate of tissue loss was similar between WBD (0.8 ± 1 mm/day, mean ± SD) and CCI (0.7 ± 0.9 mm/day). However, mortality rate by CCI in A. cervicornis was faster than in the massive species O. faveolata (0.5 ± 0.6 mm/day) and O. annularis (0.3 ± 0.3 mm/day). Tissue regeneration was at least fifteen times slower than the mortality rates for both diseases regardless of coral species. This is the first study providing coral tissue mortality and regeneration rates associated to CCI in colonies with massive morphologies, and it highlights the risks of further cover losses of the three most important reef-building species in the Caribbean

Monitoring coastal pollution associated with the largest oil refinery complex of Venezuela

This study evaluated pollution levels in water and sediments of Península de Paraguaná and related these levels with benthic macrofauna along a coastal area where the largest Venezuelan oil refineries have operated over the past 60 years. For this, the concentration of heavy metals, of hydrocarbon compounds and the community structure of the macrobenthos were examined at 20 sites distributed along 40 km of coastline for six consecutive years, which included windy and calm seasons. The spatial variability of organic and inorganic compounds showed considerably high coastal pollution along the study area, across both years and seasons. The southern sites, closest to the refineries, had consistently higher concentrations of heavy metals and organic compounds in water and sediments when compared to those in the north. The benthic community was dominated by polychaetes at all sites, seasons and years, and their abundance and distribution were significantly correlated with physical and chemical characteristics of the sediments. Sites close to the oil refineries were consistently dominated by families known to tolerate xenobiotics, such as Capitellidae and Spionidae. The results from this study highlight the importance of continuing long-term environmental monitoring programs to assess the impact of effluent discharge and spill events from the oil refineries that operate in the western coast of Paraguaná, Venezuela

Colony geometry and structural complexity of the endangered species Acropora cervicornis partly explains the structure of their associated fish assemblage

In the past decade, significant efforts have been made to describe fish-habitat associations. However, most studies have oversimplified actual connections between fish assemblages and their habitats by using univariate correlations. The purpose of this study was to identify the features of habitat forming corals that facilitate and influences assemblages of associated species such as fishes. For this we developed three-dimensional models of colonies of Acropora cervicornis to estimate geometry (length and height), structural complexity (i.e., volume, density of branches, etc.) and biological features of the colonies (i.e., live coral tissue, algae). We then correlated these colony characteristics with the associated fish assemblage using multivariate analyses. We found that geometry and complexity were better predictors of the structure of fish community, compared to other variables such as percentage of live coral tissue or algae. Combined, the geometry of each colony explained 40% of the variability of the fish assemblage structure associated with this coral species; 61% of the abundance and 69% of fish richness, respectively. Our study shows that three-dimensional reconstructions of discrete colonies of Acropora cervicornis provides a useful description of the colonial structural complexity and may explain a great deal of the variance in the structure of the associated coral reef fish community. This demonstration of the strongly trait-dependent ecosystem role of this threatened species has important implications for restoration and conservation efforts

Variation in 16S rRNA gene fingerprints between sample types (Biofilm, SML and water column), for March 2009 (summer); (a) Composite DGGE image standardised for gel-to-gel comparison using BioNumerics, (b) Multidimensional scaling (MDS) plot based on relative band intensity from composite DGGE profile.

<p>Variation in 16S rRNA gene fingerprints between sample types (Biofilm, SML and water column), for March 2009 (summer); (a) Composite DGGE image standardised for gel-to-gel comparison using BioNumerics, (b) Multidimensional scaling (MDS) plot based on relative band intensity from composite DGGE profile.</p