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Brocke H.J.,Max Planck Institute for Marine Microbiology | Brocke H.J.,Leibniz Center for Tropical Marine Ecology | Brocke H.J.,CNRS Insular Research Center and Environment Observatory | Polerecky L.,Max Planck Institute for Marine Microbiology | And 7 more authors.
PLoS ONE | Year: 2015

Benthic cyanobacterial mats (BCMs) are impacting coral reefs worldwide. However, the factors and mechanisms driving their proliferation are unclear. We conducted a multi-year survey around the Caribbean island of Curaçao, which revealed highest BCM abundance on sheltered reefs close to urbanised areas. Reefs with high BCM abundance were also characterised by high benthic cover of macroalgae and low cover of corals. Nutrient concentrations in the water-column were consistently low, but markedly increased just above substrata (both sandy and hard) covered with BCMs. This was true for sites with both high and low BCM coverage, suggesting that BCM growth is stimulated by a localised, substrate-linked release of nutrients from the microbial degradation of organic matter. This hypothesis was supported by a higher organic content in sediments on reefs with high BCM coverage, and by an in situ experiment which showed that BCMs grew within days on sediments enriched with organic matter (Spirulina). We propose that nutrient runoff from urbanised areas stimulates phototrophic blooms and enhances organic matter concentrations on the reef. This organic matter is transported by currents and settles on the seabed at sites with low hydrodynamics. Subsequently, nutrients released from the organic matter degradation fuel the growth of BCMs. Improved management of nutrients generated on land should lower organic loading of sediments and other benthos (e.g. turf and macroalgae) to reduce BCM proliferation on coral reefs. © 2015 Brocke et al. Source


Filatov M.V.,University of Amsterdam | Frade P.R.,University of Vienna | Bak R.P.M.,Netherlands Institute for Sea Research | Vermeij M.J.A.,Caribbean Research and Management of Biodiversity CARMABI Foundation | And 2 more authors.
PLoS ONE | Year: 2013

A major challenge in coral biology is to find the most adequate and phylogenetically informative characters that allow for distinction of closely related coral species. Therefore, data on corallite morphology and genetic data are often combined to increase phylogenetic resolution. In this study, we address the question to which degree genetic data and quantitative information on overall coral colony morphologies identify similar groupings within closely related morphospecies of the Caribbean coral genus Madracis. Such comparison of phylogenies based on colony morphology and genetic data will also provide insight into the degree to which genotype and phenotype overlap. We have measured morphological features of three closely related Caribbean coral species of the genus Madracis (M. formosa, M. decactis and M. carmabi). Morphological differences were then compared with phylogenies of the same species based on two nuclear DNA markers, i.e. ATPSα and SRP54. Our analysis showed that phylogenetic trees based on (macroscopical) morphological properties and phylogenetic trees based on DNA markers ATPSα and SRP54 are partially similar indicating that morphological characteristics at the colony level provide another axis, in addition to commonly used features such as corallite morphology and ecological information, to delineate genetically different coral species. We discuss this new method that allows systematic quantitative comparison between morphological characteristics of entire colonies and genetic data. © 2013 Filatov et al. Source


Frade P.R.,National Autonomous University of Mexico | Frade P.R.,Netherlands Institute for Sea Research | Frade P.R.,University of Amsterdam | Frade P.R.,Caribbean Research and Management of Biodiversity CARMABI Foundation | And 8 more authors.
Molecular Phylogenetics and Evolution | Year: 2010

Introgressive hybridization is described in several phylogenetic studies of mass-spawning corals. However, the prevalence of this process among brooding coral species is unclear. We used a mitochondrial (mtDNA: nad5) and two nuclear (nDNA: ATPSα and SRP54) intron markers to explore species barriers in the coral genus Madracis and address the role of hybridization in brooding systems. Specimens of six Caribbean Madracis morphospecies were collected from 5 to 60. m depth at Buoy One, Curaçao, supplemented by samples from Aruba, Trinidad & Tobago and Bermuda. Polymerase chain reaction and denaturing gradient gel electrophoresis were coupled to detect distinct alleles within single colonies. The recurrent nDNA phylogenetic non-monophyly among taxa is only challenged by Madracis senaria, the single monophyletic species within the genus. nDNA AMOVAs indicated overall statistical divergence (0.1% significance level) among species but pairwise comparisons of genetic differentiation revealed some gene exchange between Madracis taxa. mtDNA sequences clustered in two main groups representing typical shallow and deep water Madracis species. Madracis pharensis shallow and deep colonies (with threshold at about 23-24. m) clustered in different mtDNA branches, together with their depth-sympatric congenerics. This divergence was repeated for the nDNA (ATPSα) suggestive of distinct M. pharensis depth populations. These matched the vertical distribution of the dinoflagellate symbionts hosted by M. pharensis, with Symbiodinium ITS2 type B7 in the shallows but type B15 in the deep habitats, suggesting symbiont-related disruptive selection. Recurrent non-monophyly of Madracis taxa and high levels of shared polymorphism reflected in ambiguous phylogenetic networks indicate that hybridization is likely to have played a role in the evolution of the genus. Using coalescent forward-in-time simulations, lineage sorting alone was rejected as an explanation to the SRP54 genetic variation contained in Madracis mirabilis and Madracis decactis (species with an old fossil record), showing that introgressive hybridization has taken place between these species, either directly or through the gene pool of other Madracis taxa. Madracis widespread non-monophyly and the absence of statistical divergence between some species suggest that introgressive hybridization plays an important role in the evolution of the genus. Different reproductive traits and symbiont signatures of taxa forming distinct genetic clusters also point to the same conclusion. We suggest that Madracis morphospecies remain recognizable because introgressive hybridization is non-pervasive and/or because disruptive selection is in action. © 2010 Elsevier Inc. Source


Frade P.R.,University of Vienna | Frade P.R.,Caribbean Research and Management of Biodiversity CARMABI Foundation | Roll K.,University of Vienna | Bergauer K.,University of Vienna | And 2 more authors.
PLoS ONE | Year: 2016

Comparative studies on the distribution of archaeal versus bacterial communities associated with the surface mucus layer of corals have rarely taken place. It has therefore remained enigmatic whether mucus-Associated archaeal and bacterial communities exhibit a similar specificity towards coral hosts and whether they vary in the same fashion over spatial gradients and between reef locations. We used microbial community profiling (terminalrestriction fragment length polymorphism, T-RFLP) and clone library sequencing of the 16S rRNA gene to compare the diversity and community structure of dominant archaeal and bacterial communities associating with the mucus of three common reef-building coral species (Porites astreoides, Siderastrea siderea and Orbicella annularis) over different spatial scales on a Caribbean fringing reef. Sampling locations included three reef sites, three reef patches within each site and two depths. Reference sediment samples and ambient water were also taken for each of the 18 sampling locations resulting in a total of 239 samples. While only 41% of the bacterial operational taxonomic units (OTUs) characterized by TRFLP were shared between mucus and the ambient water or sediment, for archaeal OTUs this percentage was 2-fold higher (78%). About half of the mucus-Associated OTUs (44% and 58% of bacterial and archaeal OTUs, respectively) were shared between the three coral species. Our multivariate statistical analysis (ANOSIM, PERMANOVA and CCA) showed that while the bacterial community composition was determined by habitat (mucus, sediment or seawater), host coral species, location and spatial distance, the archaeal community composition was solely determined by the habitat. This study highlights that mucusassociated archaeal and bacterial communities differ in their degree of community turnover over reefs and in their host-specificity. © 2016 Frade et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Frade P.R.,University of Vienna | Frade P.R.,Caribbean Research and Management of Biodiversity CARMABI Foundation | Schwaninger V.,University of Innsbruck | Glasl B.,University of Vienna | And 5 more authors.
Environmental Chemistry | Year: 2016

Environmental context Corals produce copious amounts of dimethylsulfoniopropionate (DMSP), a sulfur compound implicated in climate regulation. We studied DMSP concentrations inside corals and unveiled the linkage between DMSP availability and the abundance of DMSP-degrading bacterial groups inhabiting the corals' surface. Our findings suggest that DMSP mediates the interplay between corals and microbes, highlighting the importance of sulfur compounds for microbial processes in corals and for the resilience of coral reef ecosystems. Abstract Corals produce copious amounts of dimethylsulfoniopropionate (DMSP), a sulfur compound thought to play a role in structuring coral-associated bacterial communities. We tested the hypothesis that a linkage exists between DMSP availability in coral tissues and the community dynamics of bacteria in coral surface mucus. We determined DMSP concentrations in three coral species (Meandrina meandrites, Porites astreoides and Siderastrea siderea) at two sampling depths (5 and 25m) and times of day (dawn and noon) at Curaçao, Southern Caribbean. DMSP concentration (4-409nmolcm-2 coral surface) varied with host species-specific traits such as Symbiodinium cell abundance, but not with depth or time of sampling. Exposure of corals to air caused a doubling of their DMSP concentration. The phylogenetic affiliation of mucus-associated bacteria was examined by clone libraries targeting three main subclades of the bacterial DMSP demethylase gene (dmdA). dmdA gene abundance was determined by quantitative Polymerase Chain Reaction (qPCR) against a reference housekeeping gene (recA). Overall, a higher availability of DMSP corresponded to a lower relative abundance of the dmdA gene, but this pattern was not uniform across all host species or bacterial dmdA subclades, suggesting the existence of distinct DMSP microbial niches or varying dmdA DMSP affinities. This is the first study quantifying dmdA gene abundance in corals and linking related changes in the community dynamics of DMSP-degrading bacteria to DMSP availability. Our study suggests that DMSP mediates the regulation of microbes by the coral host and highlights the significance of sulfur compounds for microbial processes in coral reefs. © CSIRO 2016. Source

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