High environmental stress and productivity increase functional diversity along a deep-sea hydrothermal vent gradient.

Productivity and environmental stress are major drivers of multiple biodiversity facets and faunal community structure. Little is known on their interacting effects on early community assembly processes in the deep sea (>200 m), the largest environment on Earth. However, at hydrothermal vents productivity correlates, at least partially, with environmental stress. Here, we studied the colonization of rock substrata deployed along a deep-sea hydrothermal vent gradient at four sites with and without direct influence of vent fluids at 1,700-m depth in the Lucky Strike vent field (Mid-Atlantic Ridge [MAR]). We examined in detail the composition of faunal communities (>20 µm) established after 2 yr and evaluated species and functional patterns. We expected the stressful hydrothermal activity to (1) limit functional diversity and (2) filter for traits clustering functionally similar species. However, our observations did not support our hypotheses. On the contrary, our results show that hydrothermal activity enhanced functional diversity. Moreover, despite high species diversity, environmental conditions at surrounding sites appear to filter for specific traits, thereby reducing functional richness. In fact, diversity in ecological functions may relax the effect of competition, allowing several species to coexist in high densities in the reduced space of the highly productive vent habitats under direct fluid emissions. We suggest that the high productivity at fluid-influenced sites supports higher functional diversity and traits that are more energetically expensive. The presence of exclusive species and functional entities led to a high turnover between surrounding sites. As a result, some of these sites contributed more than expected to the total species and functional ß diversities. The observed faunal overlap and energy links (exported productivity) suggest that rather than operating as separate entities, habitats with and without influence of hydrothermal fluids may be considered as interconnected entities. Low functional richness and environmental filtering suggest that surrounding areas, with their very heterogeneous species and functional assemblages, may be especially vulnerable to environmental changes related to natural and anthropogenic impacts, including deep-sea mining.

Megabenthic assemblages at the southern Central Indian Ridge - Spatial segregation of inactive hydrothermal vents from active-, periphery- and non-vent sites.

Active hydrothermal vents are small-scale habitats hosting endemic fauna in a well-defined zonation around fluid effluents. The fauna of inactive hydrothermal vents and its relation to active vents and non-vent area is poorly known. Characterizing inactive areas is prerequisite to establish protected areas, especially in the context of potential seafloor massive sulfide mining, which targets inactive sites. Hierarchical clustering and Distance-based Redundancy Analysis revealed five assemblages, with significantly associated substrate types: I) active hydrothermal vent, II) periphery, III) inactive hydrothermal vent and IV) soft- and V) hard-substrate within the non-vent area. For the first time, a unique inactive faunal assemblage could be identified within the hydrothermally extinct inactive Gauss field and on adjacent hard substrates. The spatial separation from the active Edmond field and periphery and the non-vent area indicates the existence of an inactive assemblage.

Revealing higher than expected diversity of Harpacticoida (Crustacea:Copepoda) in the North Sea using MALDI-TOF MS and molecular barcoding.

The North Sea is one of the most extensively studied marine regions of the world. Hence, large amounts of molecular data for species identification are available in public repositories, and expectations to find numerous new species in this well-known region are rather low. However, molecular reference data for harpacticoid copepods from this area in particular but also for this group in general is scarce. By assessing COI barcodes and MALDI-TOF mass spectra for this group of small crustaceans, it was discovered that there is a huge unknown diversity in this area. In total, COI sequences for 548 specimens from 115 species of harpacticoid copepods are presented. Over 19% of these were new to science and ten MOTUs were found to be part of cryptic species complexes. MALDI-TOF mass spectra were assessed for 622 specimens from 75 species. Because results were in concordance with species delimitation by COI barcoding and also enabled recognition of possible cryptic species, the discriminative power of this technique for biodiversity assessments is highlighted. Findings imply, species diversity in this group may be largely underestimated and total species number can be expected to be much higher than previously assumed.

Comparison of molecular species identification for North Sea calanoid copepods (Crustacea) using proteome fingerprints and DNA sequences.

Calanoid copepods play an important role in the pelagic ecosystem making them subject to various taxonomic and ecological studies, as well as indicators for detecting changes in the marine habitat. For all these investigations, valid identification, mainly of sibling and cryptic species as well as early life history stages, represents a central issue. In this study, we compare species identification methods for pelagic calanoid copepod species from the North Sea and adjacent regions in a total of 333 specimens. Morphologically identified specimens were analysed on the basis of nucleotide sequences (i.e. partial mitochondrial cytochrome c oxidase subunit I (COI) and complete 18S rDNA) and on proteome fingerprints using the technology of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). On all three molecular approaches, all specimens were classified to species level indicated by low intraspecific and high interspecific variability. Sequence divergences in both markers revealed a second Pseudocalanus species for the southern North Sea identified as Pseudocalanus moultoni by COI sequence comparisons to GenBank. Proteome fingerprints were valid for species clusters irrespective of high intraspecific variability, including significant differences between early developmental stages and adults. There was no effect of sampling region or time; thus, trophic effect, when analysing the whole organisms, was observed in species-specific protein mass spectra, underlining the power of this tool in the application on metazoan species identification. Because of less sample preparation steps, we recommend proteomic fingerprinting using the MALDI-TOF MS as an alternative or supplementary approach for rapid, cost-effective species identification.

Epizooic metazoan meiobenthos associated with tubeworm and mussel aggregations from cold seeps of the northern Gulf of Mexico.

The abundance and higher taxonomic composition of epizooic metazoan meiobenthic communities associated with mussel and tubeworm aggregations of hydrocarbon seeps at Green Canyon, Atwater Valley, and Alaminos Canyon in depths between 1400 and 2800 m were studied and compared to the infaunal community of non-seep sediments nearby. Epizooic meiofaunal abundances of associated meiobenthos living in tubeworm bushes and mussel beds at seeps were extremely low (usually <100 ind. 10 cm(-2)), similar to epizooic meiofauna at deep-sea hydrothermal vents, and the communities were composed primarily of nematodes, copepods, ostracods, and halacarids. In contrast, epizooic meiobenthic abundance is lower than previous studies have reported for infauna from seep sediments. Interestingly, non-seep sediments contained higher abundances and higher taxonomic diversity than epizooic seep communities, although in situ primary production is restricted to seeps.