Carolina Bastidas

Connectivity of Caribbean coral populations: complementary insights from empirical and modelled gene flow

Understanding patterns of connectivity among populations of marine organisms is essential for the development of realistic, spatially explicit models of population dynamics. Two approaches, empirical genetic patterns and oceanographic dispersal modelling, have been used to estimate levels of evolutionary connectivity among marine populations but rarely have their potentially complementary insights been combined. Here, a spatially realistic Lagrangian model of larval dispersal and a theoretical genetic model are integrated with the most extensive study of gene flow in a Caribbean marine organism. The 871 genets collected from 26 sites spread over the wider Caribbean subsampled 45.8% of the 1900 potential unique genets in the model. At a coarse scale, significant consensus between modelled estimates of genetic structure and empirical genetic data for populations of the reef‐building coral Montastraea annularis is observed. However, modelled and empirical data differ in their estimates of connectivity among northern Mesoamerican reefs indicating that processes other than dispersal may dominate here. Further, the geographic location and porosity of the previously described east–west barrier to gene flow in the Caribbean is refined. A multi‐prong approach, integrating genetic data and spatially realistic models of larval dispersal and genetic projection, provides complementary insights into the processes underpinning population connectivity in marine invertebrates on evolutionary timescales.

Metal Content on the Reef Coral Porites astreoides: an Evaluation of River Influence and 35 Years of Chronology

Ten metals (Al, Ca, Cd, Cu, Cr, Fe, Hg, Pb, V and Zn) were analysed in skeletal sections of the coral Porites astreoides. Each skeletal section comprised five years of growth, and a total of 35 years of carbonate deposition was analysed from 1960 to 1995. The skeletal sections were determined through the analysis of growth bands using tomography. The corals were taken from two localities that differ in their sedimentation rate and closeness to river inputs that were considered as factors that could lead to differences in coral metal content. The concentration of most metals did not differ throughout the period of time analysed. This, together with the fact that most metals showed concentrations higher than others reported for pristine locations in the Caribbean, suggests a relatively chronic contamination of the study site established at least since 1960 for the metals analysed. Only the skeletal content of Al, Fe, Cr and Ca differed significantly between localities: (a) corals from the locality closer to the river inputs had a greater concentration of Al and Fe; (b) the difference in Cr was only due to an increased concentration in one colony, although detectable in 3 skeletal sections (15 years), and; (c) the skeletal Ca difference could be associated with different growth rates between localities.

Sedimentation Rates and Metal Content of Sediments in a Venezuelan Coral Reef

The sedimentation rate and metal content in trapped sediments were determined at four localities at the Parque Nacional Morrocoy and for a sampling period of 1 year. The sedimentation rate was inversely related to the distance from the main terrestrial sources of sediment and ranged from 44+7 to 281+46 g m-2d -n (mean+SE) for the farthest two localities (11 km apart). February through May showed the highest sedimentation rate considering all localities. Except for Ca and Hg, metals in sediments also varied inversely to the distance from terrestrial sources and ranged as follows: AI 1.01-2.57, Fe 0.70-2.08, Ca 22.3-34.8 in %; and Zn 44.6-77.9, V 19.9-41.8, Pb 18.1-35.6, Cr 18.1-31.9, Cu 6.8-40.3, Hg 0.269-0.325 in lag g i based on dry weight. A common source of metal pollution is suggested from the positive and significant correlation found between the concentrations of most metals. Only Hg was not correlated with any other metal and its concentration was relatively constant for all localities. Based on our results we speculate that reef environments of P.N. Morrocoy are being affected by long-term continuous load of sediment moderately contaminated, brought about by drainage of the neighboring rivers.

Ecological Inferences from a deep screening of the Complex Bacterial Consortia associated with the coral, Porites astreoides

The functional role of the bacterial organisms in the reef ecosystem and their contribution to the coral well‐being remain largely unclear. The first step in addressing this gap of knowledge relies on in‐depth characterization of the coral microbial community and its changes in diversity across coral species, space and time. In this study, we focused on the exploration of microbial community assemblages associated with an ecologically important Caribbean scleractinian coral, Porites astreoides, using Illumina high‐throughput sequencing of the V5 fragment of 16S rRNA gene. We collected data from a large set of biological replicates, allowing us to detect patterns of geographical structure and resolve co‐occurrence patterns using network analyses. The taxonomic analysis of the resolved diversity showed consistent and dominant presence of two OTUs affiliated with the order Oceanospirillales, which corroborates a specific pattern of bacterial association emerging for this coral species and for many other corals within the genus Porites. We argue that this specific association might indicate a symbiotic association with the adult coral partner. Furthermore, we identified a highly diverse rare bacterial ‘biosphere’ (725 OTUs) also living along with the dominant bacterial symbionts, but the assemblage of this biosphere is significantly structured along the geographical scale. We further discuss that some of these rare bacterial members show significant association with other members of the community reflecting the complexity of the networked consortia within the coral holobiont.

Bacterial assemblages shifts from healthy to yellow band disease states in the dominant reef coral Montastraea faveolata.

Descriptions of microbial diversity in healthy and diseased corals are necessary first steps before further investigating the mechanisms that lead to coral pathology. This is the first study that characterizes the microbial associates from healthy corals to yellow band disease (YBD) lesions using two complementary screening techniques of bacterial 16S rRNA genes [amplified 16S ribosomal DNA restriction analysis (ARDRA) of clone libraries and denaturing gradient gel electrophoresis (DGGE)]. Both these techniques showed similar trends, namely a significant difference in the bacterial community and an increase in diversity from healthy to YBD diseased lesions. There was an increase in the number of sequences retrieved of potentially pathogenic bacteria in diseased tissues compared with healthy samples, most notably from the genus Vibrio. Furthermore, we also detected a number of known pathogenic bacteria within the natural healthy microbiota such as Vibrio carchariae and Vibrio harveyi, a result supporting previous studies, showing healthy corals have the ability to harbour these species.

First report of folliculinid ciliates affecting Caribbean scleractinian corals

This is the first report of a ciliate of the genus Halofolliculina infecting hard coral species of six families (Acroporidae, Agaricidae, Astrocoeniidae, Faviidae, Meandrinidae and Poritidae) and milleporids in the Caribbean. Surveys conducted during 2004–2005 in Venezuela, Panama and México confirmed that this ciliate affects up to 25 scleractinian species. The prevalence of this ciliate at the coral community level was variable across sites, being most commonly found at Los Roques, Venezuela, and at Bocas del Toro, Panama (prevalence 0.2–2.5%), but rarely observed in the Mexican Caribbean. Ciliates were more prevalent within populations of acroporids (Acropora palmata, Acropora cervicornis and Acropora prolifera) in Los Roques. Recent observations also corroborate the presence of these ciliates in Curacao and Puerto Rico. Our observations indicate that ciliates affecting corals have a wider distribution than previously thought, and are no longer exclusively found in the Indo-Pacific and Red Sea.

High densities of the Elkhorn coral Acropora palmata in Cayo de Agua, Archipelago Los Roques National Park, Venezuela

We observed high densities of Acropora palmata in Cayo de Agua, a coralline key in the southwestern edge of Los Roques National Park, Venezuela, including adults (>30 cm), juveniles, and recruits (<5 cm diameter) (Fig. 1A and B). Most of these colonies had no signs of disease or damage by predation; but a few colonies showed signs of white band disease, and injuries likely produced by predation, damselfishes, and sedimentation. The living cover of A. palmata (10.5%) and the colony density (3,2 col/10 m) in Cayo de Agua were similar to or higher than those observed in the few Caribbean reefs where recovery has been reported, such as San Andrés (Garzón-Ferreira and Dı́az 2002). This is in contrast with many Florida and Caribbean localities, where A. palmata populations continue declining, or have failed to recover (levels <1% in cover or <1 colony/10 m) (Jaap 2002; Miller et al. 2003). The population of A. palmata in Cayo de Agua may have resulted from asexual reproduction of surviving colonies after the 1980s WBD outbreak, but the predominance of small size colonies suggests that sexual recruitment also takes place.

Phase I and II biotransformation and antioxidant enzymes in the coral Siderastrea siderea act as biomarkers for reproductive condition and habitat quality

Abstract In this study we examined the behaviour of biomarkers in corals combining the reproductive status of colonies and reef sites with different levels of contamination. The content of P450 and P420 and the activities of NADPH c reductase, glutathione S-transferase (GST), catalase (CAT) and superoxide dimutase (SOD) were measured in the coral Siderastrea siderea at two marine parks. Parque Nacional Morrocoy (PNM) encompasses a continental marine ecosystem largely influenced by anthropogenic impacts. In contrast, Parque Nacional Archipielago Los Roques (PNALR) is 160 km offshore and relatively less impacted. As these enzymes are also affected by reproduction, samples were taken in both parks during the reproductive and non-reproductive seasons. In both parks, NADPH c reductase and GST were higher in the reproductive than in the non-reproductive season. Differences in enzymatic content or activity in corals from the two parks were usually more prominent during the reproductive season. Hence, P450 and P420 were undetectable during the non-reproductive season, while during the reproductive season, P420 was highest in colonies from the most impacted park (PNM). Activities of NADPH c reductase, CAT and SOD were also higher at PNM than at PNALR, while GST was an exception to this trend. Our results show that the aforementioned enzymes act as biomarkers in the coral S. siderea, changing in relation to its reproductive status and with the habitat quality.

Widespread local chronic stressors in Caribbean coastal habitats

Coastal ecosystems and the livelihoods they support are threatened by stressors acting at global and local scales. Here we used the data produced by the Caribbean Coastal Marine Productivity program (CARICOMP), the longest, largest monitoring program in the wider Caribbean, to evidence local-scale (decreases in water quality) and global-scale (increases in temperature) stressors across the basin. Trend analyses showed that visibility decreased at 42% of the stations, indicating that local-scale chronic stressors are widespread. On the other hand, only 18% of the stations showed increases in water temperature that would be expected from global warming, partially reflecting the limits in detecting trends due to inherent natural variability of temperature data. Decreases in visibility were associated with increased human density. However, this link can be decoupled by environmental factors, with conditions that increase the flush of water, dampening the effects of human influence. Besides documenting environmental stressors throughout the basin, our results can be used to inform future monitoring programs, if the desire is to identify stations that provide early warning signals of anthropogenic impacts. All CARICOMP environmental data are now available, providing an invaluable baseline that can be used to strengthen research, conservation, and management of coastal ecosystems in the Caribbean basin.

Correction: Widespread local chronic stressors in Caribbean coastal habitats

[This corrects the article DOI: 10.1371/journal.pone.0188564.].