Ecology and Biogeography of Free-Living Nematodes Associated with Chemosynthetic Environments in the Deep Sea: A Review

Background: Here, insight is provided into the present knowledge on free-living nematodes associated with chemosynthetic environments in the deep sea. It was investigated if the same trends of high standing stock, low diversity, and the dominance of a specialized fauna, as observed for macro-invertebrates, are also present in the nematodes in both vents and seeps. Methodology: This review is based on existing literature, in combination with integrated analysis of datasets, obtained through the Census of Marine Life program on Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss). Findings: Nematodes are often thriving in the sulphidic sediments of deep cold seeps, with standing stock values ocassionaly exceeding largely the numbers at background sites. Vents seem not characterized by elevated densities. Both chemosynthetic driven ecosystems are showing low nematode diversity, and high dominance of single species. Genera richness seems inversely correlated to vent and seep fluid emissions, associated with distinct habitat types. Deep-sea cold seeps and hydrothermal vents are, however, highly dissimilar in terms of community composition and dominant taxa. There is no unique affinity of particular nematode taxa with seeps or vents. Conclusions: It seems that shallow water relatives, rather than typical deep-sea taxa, have successfully colonized the reduced sediments of seeps at large water depth. For vents, the taxonomic similarity with adjacent regular sediments is much higher, supporting rather the importance of local adaptation, than that of long distance distribution. Likely the ephemeral nature of vents, its long distance offshore and the absence of pelagic transport mechanisms, have prevented so far the establishment of a successful and typical vent nematode fauna. Some future perspectives in meiofauna research are provided in order to get a more integrated picture of vent and seep biological processes, including all components of the marine ecosystem

Diversity of Meiofauna from the 9°50′N East Pacific Rise across a Gradient of Hydrothermal Fluid Emissions

Background: We studied the meiofauna community at deep-sea hydrothermal vents along a gradient of vent fluid emissions in the axial summit trought (AST) of the East Pacific Rise 9 degrees 50'N region. The gradient ranged from extreme high temperatures, high sulfide concentrations, and low pH at sulfide chimneys to ambient deep-sea water conditions on bare basalt. We explore meiofauna diversity and abundance, and discuss its possible underlying ecological and evolutionary processes. Methodology/Principal Findings: After sampling in five physico-chemically different habitats, the meiofauna was sorted, counted and classified. Abundances were low at all sites. A total of 52 species were identified at vent habitats. The vent community was dominated by hard substrate generalists that also lived on bare basalt at ambient deep-sea temperature in the axial summit trough (AST generalists). Some vent species were restricted to a specific vent habitat (vent specialists), but others occurred over a wide range of physico-chemical conditions (vent generalists). Additionally, 35 species were only found on cold bare basalt (basalt specialists). At vent sites, species richness and diversity clearly increased with decreasing influence of vent fluid emissions from extreme flow sulfide chimney (no fauna), high flow pompei worm (S: 4-7, H-loge': 0.11-0.45), vigorous flow tubeworm (S: 8-23; H-loge': 0.44-2.00) to low flow mussel habitats (S: 28-31; H-loge': 2.34-2.60). Conclusions/Significance: Our data suggest that with increasing temperature and toxic hydrogen sulfide concentrations and increasing amplitude of variation of these factors, fewer species are able to cope with these extreme conditions. This results in less diverse communities in more extreme habitats. The finding of many species being present at sites with and without vent fluid emissions points to a non endemic deep-sea hydrothermal vent meiofaunal community. This is in contrast to a mostly endemic macrofauna but similar to what is known for meiofauna from shallow-water vents

Correlations between the stereochemistry and the chemical ionization spectra of epimeric 3,4-dimethyl-1,2-cyclopentanediols

The eight epimeric 3,4-dimethyl-1,2-cyclopentanediols have been investigated as bis-trimethylsilyl (TMS) ethers and as diacetates by means of isobutane chemical ionization (CI). Correlations between stereochemistry and CI spectra appear to be limited in the case of the TMS ethers. All eight diacetates, however, can be unequivocally identified from their isobutane CI spectra

Chemical ionization mass spectroscopy of some crown ethers

Methane and isobutane chemical ionization mass spectrometry is superior to the classical electron impact technique for the analysis of aliphatic macrocyclic polyethers of the 4n-crown-n type. The latter reagent gas is particularly suited for molecular weight determinations

Differentiation between regio- and stereoisomers of bicyclo[3,2,0]heptanone-2 derivatives by chemical ionization mass spectrometry

The c.i. (isobutane) mass spectral behaviour was examined for a series of bicyclo[3,2,0]heptanone 2 derivatives, produced by (2π+2π) photocycloaddition reactions. The c.i. (isobutane) data allow unequivocal differentiation between hh- and ht-regioisomers. In some cases, a further assignment of the syn or anti form can also be made on the basis of the intensity of the protonated molecule ion

Trophic specialisation of metazoan meiofauna at the Håkon Mosby Mud Volcano: fatty acid biomarker isotope evidence

We report the results of a detailed investigation on the trophoecology of two dominant meiofaunal species at the Håkon Mosby Mud Volcano (HMMV), a deep-sea cold methane-venting seep. Analyses of fatty acids (FAs) and their stable carbon isotopes were used to determine the importance of chemosynthetic nutritional pathways for the dominant copepod species (morphologically very similar to Tisbe wilsoni) inhabiting the volcano’s centre and the abundant nematode Halomonhystera disjuncta from the surrounding microbial mats. The strong dominance of bacterial biomarkers (16:1?7c, 18:1?7c and 16:1?8c) coupled with their individual light carbon isotopes signatures (d13C ranging from -52 to -81‰) and the lack of symbiotic relationships with prokaryotes (as revealed by molecular analyses and fluorescent in situ hybridisation) indicated that chemosynthetically derived carbon constitutes the main diet of both species. However, the copepod showed a stronger reliance on the utilisation of methanotrophic bacteria and contained polyunsaturated FAs of bacterial origin (20:5?3 and 22:6?3 with isotope signatures d13C H. disjuncta suggested that sulphide-oxidising bacteria constituted the main diet of this nematode. Therefore, HMMV can be regarded as a persistent deep-sea cold seep, allowing a chemosynthesisbased trophic specialisation by the dominant meiofaunal species inhabiting its sediments. The present investigation, through the determination of the fatty acid profiles, provides the first evidence for trophic specialisation of meiofauna associated with sub-habitats within a cold seep

Interdisciplinary science to support North Sea marine management: lessons learned and future demands

(IF 2.39; Q1)International audienceThe expected increase of maritime activities in the North Sea and the growing awareness of its natural environmental value require enhanced science-based environmental advice for more efficient and effective marine management. The North Sea Open Science Conference organised by the Royal Belgian Institute of Natural Sciences and the Belgian Biodiversity Platform in 2016 aimed to take stock of the present-day scientific knowledge on the North Sea ecosystem, its interactions with human activities and its management. The conference was structured along three themes: (1) ‘the scientific backbone of the North Sea ecosystem: adequacy of the knowledge base?’, (2) ‘A new era in environmental monitoring and assessment: what is at stake?’, and (3) ‘Sustainability: one for all, all for one?’. Focusing on ‘open science’, we welcomed about 200 participants from around the North Sea with different backgrounds and interests in environmental sciences. The participants were challenged to reflect on current and future challenges for the North Sea management and, in particular, to explore possible nature-friendly solutions for addressing these challenges during a series of introductory oral (69) and poster (59) presentations, and World Café and Fish Bowl participatory sessions. The participants agreed on six main actions to (1) provide a solid scientific base for marine management decisions; (2) develop society-driven research; (3) increase interdisciplinary science; (4) recognise the need for system knowledge; (5) improve communication, knowledge exchange, and collective implementation of scientific knowledge; and (6) build integrated knowledge bases. For each of these, concrete action points were identified, and this review gives the most important and relevant ones for creating the knowledge base and managerial framework for a sustainable North Sea