82 research outputs found

    Bacterial community profiles in low microbial abundance sponges

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    It has long been recognized that sponges differ in the abundance of associated microorganisms, and they are therefore termed either 'low microbial abundance' (LMA) or 'high microbial abundance' (HMA) sponges. Many previous studies concentrated on the dense microbial communities in HMA sponges, whereas little is known about microorganisms in LMA sponges. Here, two LMA sponges from the Red Sea, two from the Caribbean and one from the South Pacific were investigated. With up to only five bacterial phyla per sponge, all LMA sponges showed lower phylum-level diversity than typical HMA sponges. Interestingly, each LMA sponge was dominated by a large clade within either Cyanobacteria or different classes of Proteobacteria. The overall similarity of bacterial communities among LMA sponges determined by operational taxonomic unit and UniFrac analysis was low. Also the number of sponge-specific clusters, which indicate bacteria specifically associated with sponges and which are numerous in HMA sponges, was low. A biogeographical or host-dependent distribution pattern was not observed. In conclusion, bacterial community profiles of LMA sponges are clearly different from profiles of HMA sponges and, remarkably, each LMA sponge seems to harbour its own unique bacterial communit

    Epifaunal habitat associations on mixed and hard bottom substrates in coastal waters of Northern Norway

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    Hard and mixed seafloor substrates are an important benthic habitat in coastal northern Norway and they are known to be colonized by relatively diverse communities of sessile epifauna. These assemblages are highly susceptible to physical damage and stresses imposed by organic material from industrial and municipal sources. However, despite increasing prevalence of stressors, the diversity and distribution of benthic substrates and biological communities in coastal Arctic and sub-Arctic regions remain poorly documented. In response, this study has characterized the composition of mixed and hard bottom substrates and associated sessile epifauna in fjords in Finnmark, northern Norway, using remote sensing and an innovation low-cost towed camera method. The study fjords supported a dense covering (0.1 to 0.68 individuals m–2) of sponge taxa common to deep-water ostur sponge habitats (Geodia sp., Mycale lingua, Polymastia sp., Phakellia ventilabrum, and Axinella infundibuliformis). In addition, aggregations of the soft coral (Duva florida), the tunicate (Ascidia sp.), the seastar (Ceramaster granularis) and anemone (Hormathia digitata) were prominent fauna. The small-scale spatial patterns of the epifaunal communities in this study were primarily influenced by the local hydrodynamic regime, depth, the topographical slope and the presence of hard bedrock substrates. This description of the composition, distribution and the identification of environmental drivers of epibenthic communities is valuable for the development of predictive habitat models to manage the benthic impact of multiple stressor on these ecological valuable and vulnerable Arctic habitats.publishedVersio

    DNA barcoding of sponges (Phylum Porifera) in South Africa

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    Abstract : South Africa is renowned for its biological diversity and is a hotspot for marine invertebrates (Griffith et al., 2010), including sponges (Porifera). Despite their pivotal role for the functionality of the marine ecosystem, a reliable estimate of the species richness of sponges in South Africa is difficult. Using morphological characters for species identification has its limitations: it is hindered by the paucity and plasticity of morphological characters (Blanquer & Uriz 2007, Sperling et al., 2011) which may result in numerous species being morphologically indistinguishable, i.e. “cryptic” species. The sponge fauna of South Africa is also understudied, although this issue has begun to be addressed, with more than 40 new species described from this region over the last 10 years. It is likely that the current estimate of sponge biodiversity nonetheless remains a considerable underestimate, and numerous suspected new species remain to be described (Samaai, pers. comm.). Over the last five years, increased efforts were placed on documenting South African biodiversity, with sponges as one of the focus groups. The present study is part of this initiative, and constitutes the first genetic study on South African sponges aimed at complementing morphological data to help resolve sponge taxonomy. The results indicate that South African sponges are not as widespread as previously thought, but comprise cryptic and genetically distinct evolutionary lineages. Importantly, the results show that sponges identified from South Africa as southern hemisphere are representatives of supposedly cosmopolitan species that have been misidentified. Moreover, some species assumed to be widespread in southern Africa actually turned out to be subdivided into regional evolutionary lineages with distinct distribution ranges. In some cases the molecular data corroborated the morphological species identification, whereas in other instances the combined approach revealed the presence of species complexes. This study represents a first step in constructing a reference library for South African sponges and to advance our understanding of the diversity, biogeography and evolutionary adaptability of South African sponges.M.Sc. (Zoology

    Assessing the complex sponge microbiota: core, variable and species-specific bacterial communities in marine sponges

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    Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the world's oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations

    Estimates of Particulate Organic Carbon Flowing from the Pelagic Environment to the Benthos through Sponge Assemblages

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    Despite the importance of trophic interactions between organisms, and the relationship between primary production and benthic diversity, there have been few studies that have quantified the carbon flow from pelagic to benthic environments as a result of the assemblage level activity of suspension-feeding organisms. In this study, we examine the feeding activity of seven common sponge species from the Taputeranga marine reserve on the south coast of Wellington in New Zealand. We analysed the diet composition, feeding efficiency, pumping rates, and the number of food particles (specifically picoplanktonic prokaryotic cells) retained by sponges. We used this information, combined with abundance estimates of the sponges and estimations of the total amount of food available to sponges in a known volume of water (89,821 m3), to estimate: (1) particulate organic carbon (POC) fluxes through sponges as a result of their suspension-feeding activities on picoplankton; and (2) the proportion of the available POC from picoplankton that sponges consume. The most POC acquired by the sponges was from non-photosynthetic bacterial cells (ranging from 0.09 to 4.69 g C d−1 with varying sponge percentage cover from 0.5 to 5%), followed by Prochlorococcus (0.07 to 3.47 g C d−1) and then Synechococcus (0.05 to 2.34 g C d−1) cells. Depending on sponge abundance, the amount of POC that sponges consumed as a proportion of the total POC available was 0.2–12.1% for Bac, 0.4–21.3% for Prochlo, and 0.3–15.8% for Synecho. The flux of POC for the whole sponge assemblage, based on the consumption of prokaryotic picoplankton, ranged from 0.07–3.50 g C m2 d−1. This study is the first to estimate the contribution of a sponge assemblage (rather than focusing on individual sponge species) to POC flow from three groups of picoplankton in a temperate rocky reef through the feeding activity of sponges and demonstrates the importance of sponges to energy flow in rocky reef environments

    Benthosearcher: a machine learning based tool to ultra-fast, automatic characterization of vulnerable marine ecosystems

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    The degradation and impoverishment of the seabed that has been detected during last decades is the result of numerous variables, among which are uncontrolled exploitation of the seabed concerning its vulnerability, based on trawling gear. Intending to bring the situation under control, European fishing authorities have concluded a series of proposals to promote, define and defend Marine Vulnerable Ecosystems (VMEs), among which one of the most controversial and with the greatest social and economic impact is the veto of trawling in numerous fishing areas/grounds that currently are exploited by a large c number of vessels from many countries of the EU, which see their livelihood in danger. In the process of proposing an alternative that is attractive to both parts, we propose an automatic, real-time tool (BentoSearcher) based on artificial intelligence so that trawlers have will have the autonomy to decide whether or not to cast the net on the seabed in which the vessel is operating based on the data of benthic species detected in previous fishing hauls or trips that characterize and allow to identify vulnerable seabeds

    Investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata

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    The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species
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