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Wastewater treatment plants (WWTPs) represent major point sources of pollution in coastal systems, affecting benthic ecosystems. In the present study we assessed the potential role that WWTPs have in shaping nematode communities and established baseline knowledge of free-living nematode community structures in St. Andrew Bay, Florida. Sediment samples were collected from four sites representing areas of WWTP outflow and areas with no apparent outflow, during the winter and summer. Nematode communities across sites were significantly different, and the differences were strongly associated with the distance to the nearest WWTP. While the communities were not different along transects at each site, nor across seasons, community dissimilarity across sites was high, implying strong contrasts throughout the bay system. Dominance of tolerant, opportunistic genera and Ecological Quality Status assessments suggest that the system is stressed by organic enrichment, possibly linked to the WWTPs. Our results suggest that knowledge on the life-history of dominant genera is imperative to assess the ecological quality of a benthic system, in addition to taxonomic and functional metrics. Considering the value of marine nematodes as bioindicators, more work should be done to monitor temporal variability in nematode communities in this system as future infrastructure changes alter its dynamics.

A better understanding of deep-sea biology requires knowledge of the structure and function of their communities, the spatial, temporal, and environmental patterns, and the changes and dynamics that govern them. Some of the most studied patterns in deep-sea biology are those related to bathymetrical gradients. For meiofauna and nematodes, such studies have highlighted the importance of recognizing regional differences in using ecological mechanisms to explain those patterns. Despite holding significant fisheries and oil and gas resources, the eastern Brazilian Continental Margin is poorly understood with respect to its seafloor biology and ecology. To answer ecological questions of deep-sea infaunal structural and functional diversity in relation to bathymetrical patterns, we used nematode data from five bathymetric transects (400, 1000, 1900, 2500, and 3000 m water depth) sampled in 2011 and 2013 on the Esp&iacute, rito Santo slope off the coast of southeast (SE) Brazil. Deep nematode community analysis based on 6763 nematode identifications showed very high levels of diversity (201 genera, 43 families) compared to other ocean basins and deep-sea regions. Our analyses showed that there is a distinct bathymetric break in standing stocks and community structure between 1000 and 1900 m. Nematode standing stocks were much higher at 400 and 1000 m compared to those for similar depths worldwide, likely linked to the intense and frequent upwelling and specific hydrographic and topographic identity of the region. The bathymetric break was not present for structural and functional nematode diversity. Instead, bathymetric regressions showed that they increased gradually toward 3000 m water depth. The deep Esp&iacute, rito Santo basin is characterized by rich and equitable nematode communities that are both mature and trophically diverse. General deep-sea ecological theories apply to our findings, but there are also substantial regional effects related to the local margin topography, upwelling, and oceanographic and hydrodynamic processes that make the Esp&iacute, rito Santo Basin a unique and diverse deep-sea ecosystem.

The calving of A-68, the 5,800-km2, 1-trillion-ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice-shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large-scale modifications to Southern Ocean ecosystems and continental ice movements, with global-scale implications. The thinning and rate of future ice-shelf demise is notoriously unpredictable, but models suggest increased shelf-melt and calving will become more common. To date, little is known about sub-ice-shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice-shelf melt, volume loss, retreat, and calving, (b) ice-shelf-associated ecosystems through sub-ice, sediment-core, and pre-collapse and post-collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps. This article is categorized under: Climate, Ecology, and Conservation > Modeling Species and Community Interactions.

The composition, spatial structure, diversity and abundance of Antarctic nematode and copepod meiobenthic communities was examined in shallow (5–25 m) marine coastal sediments at Casey Station, East Antarctica. The sampling design incorporated spatial scales ranging from 10 meters to kilometers and included testing for human impacts by comparing polluted (metal and hydrocarbon contaminated sediments adjacent to old waste disposal sites) and control areas. A total of 38 nematode genera and 20 copepod families were recorded with nematodes being dominant, comprising up to 95% of the total abundance. Variation was greatest at the largest scale (km’s) but each location had distinct assemblages. At smaller scales there were different patterns of variation for nematodes and copepods. There were significant differences between communities at control and impacted locations. Community patterns had strong correlations with concentrations of metals introduced by human activity in sediments as well as sediment grain size and total organic content. Given the strong association with environmental patterns, particularly those associated with human impacts, we provide further evidence that meiofauna are very useful indicators of anthropogenic environmental changes in Antarctica.

The deep sea (>200 m depth) encompasses >95% of the world’s ocean volume and represents the largest and least explored biome on Earth (

The meiofauna represent a highly informative faunal group for ecological evaluation in marine ecosystems, but few studies have investigated their spatial distribution patterns in tidal creeks. As an important component of the tidal flat, tidal creeks tend to have unique, contrasting habitats associated with erosion and accretion beds within a short distance of each other. The gradient represented by these habitats is expected to have consequences on the meiofauna and nematode communities. Based on sediment samples from two tidal creeks on a tidal flat covered with very fine-grained sediments, we show that there are distinct relationships between the benthic habitats, meiofauna/nematode communities and the erosion/accretion status of the tidal creek bed. Although there were no differences in sediment grain size between the eroding and accretion sides of the creek, higher sedimentary phaeopigment, total organic carbon and water contents were observed at the accreting side compared to the eroding side. The meiofauna exhibited a significant spatial variability between the two sides. The dominant taxon, nematodes, was more abundant on the accretion side, whilst copepods were more abundant on the erosion side of the creeks. The nematode/copepod ratio was in agreement with the observation that more pollutants and/or organic matter settled down on the accretion side. A total of 53 nematode genera were identified, belonging to 3 orders and 22 families. The prevalence of tolerant nematode genera such as Desmodora, Sabatieria and Viscosia , suggested that nematodes inhabiting highly dynamic environments are well adapted to the physical disturbance. Our results show that geomorphic evolution as implied by erosion/accretion patterns are reflected in the meiofauna and nematode communities and can be assessed using different community characteristics.

Results from a 1D setup of the European Regional Seas Ecosystem Model (ERSEM) biogeochemical model were compared with new observations collected under the UK Shelf Seas Biogeochemistry (SSB) programme to assess model performance and clarify elements of shelf-sea benthic biogeochemistry and carbon cycling. Observations from two contrasting sites (muddy and sandy) in the Celtic Sea in otherwise comparable hydrographic conditions were considered, with the focus on the benthic system. A standard model parameterisation with site-specific light and nutrient adjustments was used, along with modifications to the within-seabed diffusivity to accommodate the modelling of permeable (sandy) sediments. Differences between modelled and observed quantities of organic carbon in the bed were interpreted to suggest that a large part (>90%) of the observed benthic organic carbon is biologically relatively inactive. Evidence on the rate at which this inactive fraction is produced will constitute important information to quantify offshore carbon sequestration. Total oxygen uptake and oxic layer depths were within the range of the measured values. Modelled depth average pore water concentrations of ammonium, phosphate and silicate were typically 5–20% of observed values at the muddy site due to an underestimate of concentrations associated with the deeper sediment layers. Model agreement for these nutrients was better at the sandy site, which had lower pore water concentrations, especially deeper in the sediment. Comparison of pore water nitrate with observations had added uncertainty, as the results from process studies at the sites indicated the dominance of the anammox pathway for nitrogen removal; a pathway that is not included in the model. Macrofaunal biomasses were overestimated, although a model run with increased macrofaunal background mortality rates decreased macrofaunal biomass and improved agreement with observations. The decrease in macrofaunal biomass was compensated by an increase in meiofaunal biomass such that total oxygen demand remained within the observed range. The permeable sediment modification reproduced some of the observed behaviour of oxygen penetration depth at the sandy site. It is suggested that future development in ERSEM benthic modelling should focus on: (1) mixing and degradation rates of benthic organic matter, (2) validation of benthic faunal biomass against large scale spatial datasets, (3) incorporation of anammox in the benthic nitrogen cycle, and (4) further developments to represent permeable sediment processes. Electronic supplementary material The online version of this article (doi:10.1007/s10533-017-0367-0) contains supplementary material, which is available to authorized users.

Warming and ocean acidification have been shown to have significant impacts on marine organisms. However, none studies have addressed the impact of these two stressors on harpacticoid copepod community structure. A mesocosm experiment was conducted to assess the potential interactive impact of different levels of elevated CO2 and temperature on an intertidal harpacticoid copepod community. Artificial substrate units (ASUs) colonized by meiofauna from the extreme low intertidal zone were exposed to eight experimental treatments (four pH levels: 8.0, 7.7, 7.3 and 6.7, crossed with two temperature levels: 12 and 16 °C). After 60 days exposure communities were significantly affected by both stressors. The dominant harpacticoid species were mainly affected at treatments held at pH 6.7, but with divergent biological response patterns. At pH 6.7 Tisbe sp and Ectinosoma sp2 exhibited important density reductions, while considerable density increases were observed for Amphiascus longarticulatus and Amphiascoides golikovi. This study has demonstrated that elevated levels of CO2 and ocean warming may have substantial effects on the structure of harpacticoid communities. Importantly, the increase in malformations observed at pH 6.7 indicated that we need to consider sub-lethal effects that could have consequences for populations after long periods of exposure.

Macroalgae drive the largest CO2 flux fixed globally by marine macrophytes. Most of the resulting biomass is exported through the coastal ocean as detritus and yet almost no field measurements have verified its potential net sequestration in marine sediments. This gap limits the scope for the inclusion of macroalgae within blue carbon schemes that support ocean carbon sequestration globally, and the understanding of the role their carbon plays within distal food webs. Here, we pursued three lines of evidence (eDNA sequencing, Bayesian Stable Isotope Mixing Modeling, and benthic-pelagic process measurements) to generate needed, novel data addressing this gap. To this end, a 13-month study was undertaken at a deep coastal sedimentary site in the English Channel, and the surrounding shoreline of Plymouth, UK. The eDNA sequencing indicated that detritus from most macroalgae in surrounding shores occurs within deep, coastal sediments, with detritus supply reflecting the seasonal ecology of individual species. Bayesian stable isotope mixing modeling [C and N] highlighted its vital role in supporting the deep coastal benthic food web (22–36% of diets), especially when other resources are seasonally low. The magnitude of detritus uptake within the food web and sediments varies seasonally, with an average net sedimentary organic macroalgal carbon sequestration of 8.75 g C·m−2·yr−1. The average net sequestration of particulate organic carbon in sediments is 58.74 g C·m−2·yr−1, the two rates corresponding to 4–5% and 26–37% of those associated with mangroves, salt marshes, and seagrass beds, systems more readily identified as blue carbon habitats. These novel data provide important first estimates that help to contextualize the importance of macroalgal-sedimentary connectivity for deep coastal food webs, and measured fluxes help constrain its role within global blue carbon that can support policy development. At a time when climate change mitigation is at the foreground of environmental policy development, embracing the full potential of the ocean in supporting climate regulation via CO2 sequestration is a necessity.

Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. Mean total densities in our sampling cores (400-1800 m water depth) were highest with 3688 ind. 10 cm-2 at the OMZ core at 400 m water depth, decreasing rapidly downslope. Nematodes were overall dominant, with a maximum of 99.9% in the OMZ core, followed by copepods (13%), nauplii (4.8%), and polychaetes (3%). Relative copepod and nauplii abundance increased consistently with depth and increasing bottom-water O2. Meiofaunal composition was significantly different among sites, with lower taxonomic diversity at OMZ sites relative to deeper, oxygenated sites. Vertical distribution patterns within sediments showed that in strongly oxygen-depleted sites less meiofauna was concentrated in the surface sediment than at deeper slope sites. Highest meiofaunal abundance and lowest diversity occurred under lowest oxygen and highest pigment levels, whereas highest diversity occurred under highest oxygen-concentrations and low CPE, as well as high quality of sedimentary pigment (chl a/phaeo) and organic carbon (C/N). The lower meiofaunal diversity, and hence lower structural and trophic complexity, at oxygen-depleted sites raises concerns about changes in the structure and function of benthic marine ecosystems in the face of OMZ expansions.

14 páginas, 6 tablas, 4 figuras, We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution of the meiofauna in the submarine Blanes Canyon, and its adjacent western slope (NW Mediterranean margin of the Iberian Peninsula). We analyzed the relationships between the main sedimentary environmental variables (i.e. grain size, Chl-a, Chl-a: phaeopigments, CPE, organic carbon and total nitrogen) and the density and structure of the meiofaunal assemblages along a bathymetric gradient (from 500 to 2000 m depth) in spring and autumn of 2012 and 2013. Twenty-one and 16 major taxa were identified for respectively the canyon and slope, where the assemblages were always dominated by nematodes. The gradual decreasing meiofaunal densities with increasing depth at the slope showed little variability among stations and corresponded with a uniform pattern of food availability. The canyon was environmentally much more variable and sediments contained greater amounts of food resources (Chl-a and CPE) throughout, leading not only to increased meiofaunal densities compared to the slope, but also different assemblages in terms of composition and structure. This variability in the canyon is only partly explained by seasonal food inputs. The high densities found at 900 m and 1200 m depth coincided with significant increases in food availability compared to shallower and deeper stations in the canyon. Our results suggest that the disruption in expected bathymetric decrease in densities at 900–1200 m water depth coincided with noticeable changes in the environmental variables typical for disturbance and deposition events (e.g., higher sand content and CPE), evoking the hypothesis of an anthropogenic effect at these depths in the canyon. The increased downward particle fluxes at 900–1200 m depth caused by bottom trawling along canyon flanks, as reported in previous studies, support our hypothesis and allude to a substantial anthropogenic factor influencing benthic assemblages at these depths. The possible relationships of the observed patterns and some major natural environmental (e.g., surface productivity or dense shelf water cascading) and anthropogenic (e.g. the lateral advection and downward transport of food-enriched sediments resuspended by the daily canyonflank trawling activities) drivers are discussed., This research has been supported by DOS MARES (Ref. CTM2010-21810-C03-03) research project, funded by the Spanish State Research Plan, and to the Consolidated Research Group on Marine Benthic Ecology of the “Generalitat de Catalunya (2014SGR120)”. C. Romano received funding from the People Programme (Marie Curie Action) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement N. PIOF-GA-2013-628146. J. Ingels was supported by a Plymouth Marine Laboratory Post-doctoral Research Fellowship in collaboration with University of Exeter and a Marie Curie Intra-European Fellowship within the 7th European Commission Framework Programme (Grant Agreement FP7-PEOPLE-2011-IEF no. 00879).

Intertidal nematode assemblages along three beaches with different types of anthropogenic activity were collected in the northern part of the Persian Gulf, near Bandar Abbas (Iran). Forty-two genera of free-living nematodes belonging to 17 families were identified. Daptonema, Ptycholaimellus, and Promonhystera were the most abundant taxa in the area. The nematode assemblage structure was negatively affected by polychlorinated biphenyls (PCBs) and total organic matter (TOM), with an impact gradient from the polluted Power Plant (PP), over Khur Gursuzan (KG), to the cleaner ‘Resalat’ site (RE). The PP sites, characterized by industrial infrastructures, were mainly impacted by PCBs, while Khur Gursuzan (KG) is under the influence of domestic discharges, with high sedimentary TOM levels. However, PCBs and TOM seem closely associated and they likely lead to compounding effects on the fauna. Among the bioindicator genera found, Spirinia, Chromadorina, and Terschellingia may be recognized as resistant taxa to PCBs, while Daptonema, Sabateria, Promonhystera and Ptycholaimellus are opportunists able to exploit organic load, and Oncholaimus and Pomponema appeared sensitive genera being characteristic to unpolluted sediments. As expected, the spatial effects between the stations and concomitantly the different types of anthropogenic impacts played a much more important role than seasonal variability and related changes. This confirms that anthropogenic impact can be a major control factor at Persian Gulf beaches. Nematode female:male ratios were in favor of the females, especially in the sediments impacted by PCBs, corroborating the hypothesis that stressful conditions sustain the increasing female frequency in nematode populations. In terms of the ecological quality (EcoQ) status, genus percentages indicated lower EcoQ at PP and highest at RE. In contrast, Shannon-Wiener diversity (H’) did not detect variations of EcoQ status at the three locations, while the Maturity Index did not indicate the presence of stressful conditions at PP, but it did at KG. It is possible that MI performs better when considering organic pollution compared to PCB contamination. However, we do not recommend its use in intertidal or transitional areas that are characterized by strong natural variations of the physical and chemical variables.

Este artículo contiene 16 páginas, 10 figuras, 1 tabla., Global concern over increasing CO2 emissions, and the resultant CO2 driven temperature rises and changes in seawater chemistry, necessitates the advancement of understanding into how these changes will affect marine life now and in the future. Here we report on an experimental investigation into the effects of increased CO2 concentration and elevated temperature on sedimentary meiofaunal communities. Cohesive (muddy) and noncohesive (sandy) sediments were collected from the Eden Estuary in St. Andrews, Scotland, UK, placed within a flume setup and exposed to 2 levels of CO2 concentration (380 and 750 ppmv, current at the time of the experiment, and predicted CO2 concentration by 2100, respectively) and 2 temperature levels (12 °C and 16 °C, current in-situ and predicted temperature by 2100, respectively). We investigated the metazoan meiofauna and nematode communities before and after 28 days of exposure under these experimental conditions. The most determinative factor for abundance, diversity and community structure of meiofauna and nematodes was sediment type: on all levels, communities were significantly different between sand and mud sediments which agrees with what is generally known about the influence of sediment structure on meiofaunal organisms. Few CO2 and temperature effects were observed, suggesting that meiofauna and nematodes are generally much less responsive than, for instance, microbial communities and macrofauna to these environmental changes in estuarine environments, where organisms are naturally exposed to a fluctuating environment. This was corroborated by the observed effects related to the different seasons in which the samples were taken from the field to run the experiment. After 28 days, meiofauna and nematode communities in muddy sediments showed a greater response to increased CO2 concentration and temperature rise than in sandy sediments. However, further study is needed to investigate the underlying mechanisms and meiofauna species-specific resilience and responses to ocean acidification and warming, and their interactions with other biota, to understand what such changes may mean for meiofauna communities and the ecosystem processes and functions they contribute to., Authors acknowledge support through the NERC OA programme. PJS acknowledges support from the UK Natural Environment Research Council through National Capability funding and, with the Department for Environment, Food and Rural Affairs, through the Marine Ecosystems Research Programme (grant number NE/L003279/1). JI was supported by a Plymouth Marine Laboratory Post-doctoral Research Fellowship in collaboration with University of Exeter and a Marie Curie Intra-European Fellowship within the 7th European Commission Framework Programme (Grant Agreement FP7-PEOPLE- 2011-IEF no. 00879).

Este artículo contiene 18 páginas, 7 figuras y 7 tablas, Within the framework of the DosMares project, we investigated the standing stocks, structural and functional diversity and community structure of the nematode assemblages both along a bathymetric gradient, and the vertical sediment profile (0–5 cm) in the Blanes Canyon (NW Mediterranean) during autumn 2012. The standing stocks (total density and biomass) did not follow the traditional pattern of bathymetric decline, showing disrupting peaks at 1200 and 1750 m depth. Along the sediment profile, high densities occurred in surface sediment layers, mainly due to increased nematode abundance, while biomass did not show clear general trends. Structural and functional diversity did not exhibit consistent bathymetric gradients, and were not related to sedimentary variables, except for positive correlations with clay and silt contents. However, structural and functional diversity decreased significantly along the vertical sediment profile. The analysis of the nematode community assemblages allowed us to identify three different community structure zones along the canyon axis: upper (ca. 500–1200 m depth), middle (ca. 1500–1750 m depth) and deeper (ca. 2000 m depth), which were 1) followed the canyon topographic heterogeneity, 2) supported by the environmental analyses (food sources and grain size), and 3) were reflected in the variable sediment and organic matter inputs from canyon walls and adjacent margins. The nematode distribution along the vertical sediment profile also varied in the three zones, mainly owing to differences in the respective surface sediment layers. Deeper sediment layers were similar, mainly caused by to the high abundance of Sabatieria. Our results indicate that, in addition to the expected influence of the canyon's topography and hydrodynamic regimes, the nematode community from Blanes Canyon were controlled by the sedimentary characteristics and available food sources. Moreover, our results and additional data from other research in and around Blanes Canyon suggest that observed anthropogenic pressure in the surrounding areas (mainly derived from regular and persistent trawling activities) plays a key role in explaining the sedimentary pattern along the canyon axis and the observed nematode assemblage distribution., This research has been supported by DOS MARES (Ref. CTM2010-21810-C03-03) research project, funded by the Spanish State Research Plan, and to the Consolidated Research Group on Marine Benthic Ecology of the “Generalitat de Catalunya (2014SGR120)”. J. Ingels was partially supported by a Plymouth Marine Laboratory Post-doctoral Research Fellowship in collaboration with University of Exeter and a Marie Curie Intra-European Fellowship within the 7th European Commission Framework Programme (Grant Agreement FP7-PEOPLE-2011-IEF no. 00879).

Despite recent advances in the knowledge of submarine canyons ecosystems, our understanding of the faunal patterns and processes in these environments is still marginal. In this study, meiobenthic nematode communities (from 300 m to 1600 m depth) obtained in November 2003 and May 2004 at eight stations inside and outside Blanes submarine canyon were analysed for nematode standing stocks (SSs), feeding types and gender-life stage distributions. Environmental data were obtained by sediment traps and current meters, attached to moorings (April 2003–May 2004), and sediments samples analysed for biogeochemistry and grain size (May 2004). In November 2003, nematode SSs decreased with increasing depth (367.2 individuals and 7.31 μg C per 10 cm2 at 388 m water depth to 7.7 individuals and 0.18 μg C per 10 cm2 at 1677 m water depth), showing a significant negative relation (abundance: R2 = 0.620, p = 0.020; biomass: R2 = 0.512, p = 0.046). This was not the case in May 2004 (283.5 individuals and 3.53 μg C per 10 cm2 at 388 m water depth to 490.8 individuals and 4.93 μg C per 10 cm2 at 1677 m water depth; abundance: R2 = 0.003, p = 0.902; biomass: R2 = 0.052, p = 0.587), suggesting a temporal effect that overrides the traditional decrease of SSs with increasing water depth. Both water depth and sampling time played a significant role in explaining nematode SSs, but with differences between stations. No overall differences were observed between canyon and open slope stations. Nematode standing stock (SS) patterns can be explained by taking into account the interplay of phytodetrital input and disturbance events, with station differences such as topography playing an important role. Individual nematode size decreased from November 2003 to May 2004 and was explained by a food-induced genera shift and/or a food-induced transition from a ‘latent’ to a ‘reproductive’ nematode community. Our results suggest that size patterns in nematode communities are not solely governed by trophic conditions over longer periods of time in relatively food-rich environments such as canyons. We hypothesize that food pulses in a dynamic and topographical heterogeneous environment such as canyons regulate nematode size distributions, rather than long-term food availability. Feeding type distributions in the Blanes Canyon did not clearly resemble those from other canyon systems, apart from the spring assemblage at one station in the head of the canyon.

The urge to understand spatial distributions of species and communities and their causative processes has continuously instigated the development and testing of conceptual models in spatial ecology. For the deep sea, there is evidence that structural and functional characteristics of benthic communities are regulated by a multitude of biotic and environmental processes that act in concert on different spatial scales, but the spatial patterns are poorly understood compared to those for terrestrial ecosystems. Deep-sea studies generally focus on very limited scale ranges, thereby impairing our understanding of which spatial scales and associated processes are most important in driving structural and functional diversity of communities. Here, we used an extensive integrated dataset of free-living nematodes from deep-sea sediments to unravel the importance of different spatial scales in determining benthic infauna communities. Multiple-factor multivariate permutational analyses were performed on different sets of community descriptors (structure, structural and functional diversity, standing stock). The different spatial scales investigated cover two margins in the northeast Atlantic, several submarine canyons/channel/slope areas, a bathymetrical range of 700–4300 m, different sampling locations at each station, and vertical sediment profiles. The results indicated that the most important spatial scale for structural and functional diversity and standing stock variability is the smallest one; infauna communities changed substantially more with differences between sediment depth layers than with differences associated to larger geographical or bathymetrical scales. Community structure differences were greatest between stations at both margins. Important regulating ecosystem processes and the scale on which they occur are discussed. The results imply that, if we are to improve our understanding of ecosystem patterns of deep-sea infauna and the relevant processes driving their structure, structural and functional diversity, and standing stock, we must pay particular attention to the small-scale heterogeneity or patchiness and the causative mechanisms acting on that scale.

Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale. Electronic supplementary material The online version of this article (doi:10.1007/s10533-017-0366-1) contains supplementary material, which is available to authorized users.

Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed.

Submarine canyon systems provide a heterogeneous habitat for deep-sea benthos in terms of topography, hydrography, and the quality and quantity of organic matter present. Enhanced meiofauna densities as found in organically enriched canyon sediments suggest that nematodes, as the dominant metazoan meiobenthic taxon, may play an important role in the benthic food web of these sediments. Very little is known about the natural diets and trophic biology of deep-sea nematodes, but enrichment experiments can shed light on nematode feeding selectivity and trophic position. An in-situ pulse-chase experiment (Feedex) was performed in the Nazare Canyon on the Portuguese margin in summer 2007 to study nematode feeding behaviour. 13C-labelled diatoms and bacteria were added to sediment cores which were then sampled over a 14-day period. There was differential uptake by the nematode community of the food sources provided, indicating selective feeding processes. 13C isotope results revealed that selective feeding was less pronounced at the surface, compared to the sediment subsurface. This was supported by a higher trophic diversity in surface sediments (Θ−1 = 3.50 ± 0.2) compared to the subsurface (2.78 ± 0.6), implying that more food items may be used by the nematode community at the sediment surface. Predatory and scavenging nematodes contributed relatively more to biomass than other feeding types and can be seen as key contributors to the nematode food web at the canyon site. Non-selective deposit feeding nematodes were the dominant trophic group in terms of abundance and contributed substantially to total nematode biomass. The high levels of ‘fresh’ (bioavailable) organic matter input and moderate hydrodynamic disturbance of the canyon environment lead to a more complex trophic structure in canyon nematode communities than that found on the open continental slope, and favours predator/scavengers and non-selective deposit feeders.

The great variety of geological and hydrological conditions in the deep sea generates many different habitats. Some are only recently explored, although their true extent and geographical coverage are still not fully established. Both continental margins and mid-oceanic seafloors are much more complex ecologically, geologically, chemically and hydrodynamically than originally thought. As a result, fundamental patterns of species distribution first observed and explained in the context of relatively monotonous slopes and abyssal plains must now be re-evaluated in the light of this newly recognized habitat heterogeneity. Based on a global database of nematode genus composition, collected as part of the Census of Marine Life, we show that macrohabitat heterogeneity contributes significantly to total deep-sea nematode diversity on a global scale. Different deep-sea settings harbour specific nematode assemblages. Some of them, like coral rubble zones or nodule areas, are very diverse habitats. Factors such as increased substrate complexity in the case of nodules and corals seem to facilitate the co-existence of a large number of genera with different modes of life, ranging from sediment dwelling to epifaunal. Furthermore, strong biochemical gradients in the case of vents or seeps are responsible for the success of particular genera, which are not prominent in more typical soft sediments. Many nematode deep-sea genera are cosmopolitan, inhabiting a variety of deep-sea habitats and oceans, whereas only 21% of all deep-sea genera recorded are restricted to a single habitat. In addition to habitat heterogeneity, regional differences are important in structuring nematode assemblages. For instance, seeps from different regions yield different genera that thrive on the sulphidic sediments. This study also shows that many areas and habitats remain highly under-sampled, affecting our ability to understand fully the contribution of habitat heterogeneity versus regional differences to global nematode diversity.

The deep sea is often viewed as a vast, dark, remote, and inhospitable environment, yet the deep ocean and seafloor are crucial to our lives through the services that they provide. Our understanding of how the deep sea functions remains limited, but when treated synoptically, a diversity of supporting, provisioning, regulating and cultural services becomes apparent. The biological pump transports carbon from the atmosphere into deep-ocean water masses that are separated over prolonged periods, reducing the impact of anthropogenic carbon release. Microbial oxidation of methane keeps another potent greenhouse gas out of the atmosphere while trapping carbon in authigenic carbonates. Nutrient regeneration by all faunal size classes provides the elements necessary for fueling surface productivity and fisheries, and microbial processes detoxify a diversity of compounds. Each of these processes occur on a very small scale, yet considering the vast area over which they occur they become important for the global functioning of the ocean. The deep sea also provides a wealth of resources, including fish stocks, enormous bioprospecting potential, and elements and energy reserves that are currently being extracted and will be increasingly important in the near future. Society benefits from the intrigue and mystery, the strange life forms, and the great unknown that has acted as a muse for inspiration and imagination since near the beginning of civilization. While many functions occur on the scale of microns to meters and timescales up to years, the derived services that result are only useful after centuries of integrated activity. This vast dark habitat, which covers the majority of the globe, harbors processes that directly impact humans in a variety of ways; however, the same traits that differentiate it from terrestrial or shallow marine systems also result in a greater need for integrated spatial and temporal understanding as it experiences increased use by society. In this manuscript we aim to provide a foundation for informed conservation and management of the deep sea by summarizing the important role of the deep sea in society.

The deep sea is Earth’s largest habitat but little is known about the nature of deep-sea parasitism. In contrast to a few characterized cases of bacterial and protistan parasites, the existence and biological significance of deep-sea parasitic fungi is yet to be understood. Here we report the discovery of a fungus-related parasitic microsporidium, Nematocenator marisprofundi n. gen. n. sp. that infects benthic nematodes at Pacific Ocean methane seeps on the Pacific Ocean floor. This infection is species-specific and has been temporally and spatially stable over two years of sampling, indicating an ecologically consistent host-parasite interaction. A high distribution of spores in the reproductive tracts of infected males and females and their absence from host nematodes’ intestines suggests a sexual transmission strategy in contrast to the fecal-oral transmission of most microsporidia. N. marisprofundi targets the host’s body wall muscles causing cell lysis, and in severe infection even muscle filament degradation. Phylogenetic analyses placed N. marisprofundi in a novel and basal clade not closely related to any described microsporidia clade, suggesting either that microsporidia-nematode parasitism occurred early in microsporidia evolution or that host specialization occurred late in an ancient deep-sea microsporidian lineage. Our findings reveal that methane seeps support complex ecosystems involving interkingdom interactions between bacteria, nematodes, and parasitic fungi and that microsporidia parasitism exists also in the deep sea biosphere.

Genus Dystomanema Bezerra, Pape, Hauquier, Ingels & Vanreusel gen. nov. Diagnosis. Neotonchinae. Body long, cylindrical, tapering anteriorly. Cuticle transversally striated with fine punctation, more evident in the tail region. No lateral differentiation. Few somatic setae with no fixed distribution pattern. Anterior sensilla arranged in three circles 6 + 6 + 4, first circle papilliform, outer circles setiform. Dorsosublateral setae just posterior to the third circle of sensilla at the level of the amphid. Spiral amphid smaller in females than in males. Oral opening ventrally displaced. Buccal cavity wide, deep, funnel shaped. Gymnostom followed by well-cuticularized pharyngostom with expanded conical posterior part. Three small teeth, one dorsal tooth and two smaller subventral teeth, all situated in the pharyngostom. Pharynx cylindrical with a posterior muscular bulb. Male reproductive system diorchic, spicules of equal size, one ventral precloacal spine and conspicuous cup-shaped precloacal supplements. Female reproductive system didelphic, ovaries antidromously reflexed. Tail conical. Type species. Dystomanema cadizensis sp. nov.; present paper. One other species in genus: Dystomanema brandtae sp. nov.; present paper Differential diagnosis. Dystomanema gen. nov. resembles Comesa Gerlach, 1956 and Neothonchus Cobb, 1933 in terms of the body shape, cuticle pattern and shape of supplements, but differentiates from both in having much smaller dorsal tooth. In the subfamily Ethmolaiminae, Ethmolaimus de Man, 1880 (syn. Trichethmolaimus, Jensen 1994) and Paraethmolaimus Jensen, 1994 has long mouth and massive teeth; in the subfamily Neotonchinae, Comesa Gerlach, 1956 has a distinct dorsal tooth and ventral ridges; Gomphionema Wieser & Hopper, 1966 has a massive dorsal tooth; Gomphionchus Platt, 1982 and Neothonchus Cobb, 1933 has a big dorsal tooth; Nannolaimus Cobb, 1920 has a small weakly cuticularized dorsal tooth while Filitonchoides Jensen, 1985 and Filitonchus Platt, 1982 has a poorly developed buccal cavity with no sign of a dorsal tooth. Comesa Gerlach, 1956 species with small teeth also have a developed dorsal tooth. Dystomanema gen. nov. has no developed dorsal tooth but three small teeth (one dorsal and two subventral) instead. These small teeth are bigger than the ridges mentioned for Comesa Gerlach, 1956. Dystomanema gen. nov. might represent a transition between no teeth (Filitonchoides Jensen, 1985 and Filitonchus Platt, 1982) and small teeth (some Comesa Gerlach, 1956) to big teeth in this subfamily. Differs from all genera of the family by the ventrally displaced oral opening (visible at low magnification). Subterminal oral opening is observed in other nematoda genera, such as Campylaimus Cobb, 1920, Diplopeltula Gerlach, 1950 and Morlaixia Vincx and Gourbault 1988. Just some Campylaimus (Cobb, 1920) and Morlaixia Vincx and Gourbault 1988 (genus also found in cold-seeps by Guilini et al., 2012) have a subventrally displaced oral opening. Diplopeltula Gerlach, 1950 has a dorsal oral opening. The ventral position of the oral opening, in some Campylaimus, was not accepted by Vincx and Gourbault, 1988 when they described the genus Morlaixia Vincx and Gourbault, 1988 but Villares et al. (2013) accept this ventral position and provide a key to species identification. Etymology. The genus is named after the particular mouth displacement, a characteristic that is unique in the family. Dystomanema cadizensis gen. nov. sp. nov. (Figs 4 A���F, 5 A���H, 6 A���F; Table 1) Material examined. Holotype male (Inventory No. UGMD 104262), three paratypes males (Inventory No. UGMD 104263, 104264, 104265), three paratypes females (Inventory No. UGMD 104266, 104267, 104268). Type habitat and locality. Cold-seep sediments in the Northeast Atlantic, Gulf of C��diz, Darwin mud volcano (35 �� 23.51 ��� N 7 �� 11.48 ���W). Description. Males: Body slender, long, uniform in diameters tapering anteriorly and posteriorly. Fixation shape uncoiled. Cuticle transversally striated with fine punctation more evident on the tail region. No lateral differentiation. Few somatic setae with no fixed distribution pattern. Head conical, low lips. Inner labial sensilla papilliform, six outer-labial short setiform sensilla, four cephalic setae 5 ��m or 35 % of corresponding body diameter long. Short dorso-sublateral subcephalic setae present. Amphid spiral, ventrally to the centre, 3 turns. Mouth opening ventrally displaced. Buccal cavity wide, deep (18 ��m), funnel shaped. Gymnostom followed by well-cuticularized pharyngostom with expanded conical posterior part. Sclerotized walls of pharyngostom with three small teeth: a dorsal tooth and two smaller subventral teeth. Pharynx cylindrical with a posterior muscular bulb. Nerve ring located slightly anterior to middle of pharynx. Secretory excretory pore located immediately after cephalic setae. Reproductive system with long vas deferens, clear patch of variable position from the level of the 4 th to the 8 th supplement from the cloaca. Outstretched testes anteriorly directed, anterior one to the right of intestine and posterior one, smaller, to the left. Spicules of equal size, about the same length as the cloacal diameter, slightly cephalated, bent about 1 / 3 of the distance from the distal end. Gubernaculum plate-like with a sclerotized rod-like internal structure at the distal half. Ten to twelve conspicuous cup-shaped precloacal supplements with external longitudinal articulated flange. Distance between the supplements variable among the males. Prominent ventral precloacal spine about 16 ��m anterior to the cloacal opening. At the opening of the cloaca there is a slightly sclerotized triangular structure, which seems to be a cuticular projection. Tail conical plump, with bluntly rounded tip. Three caudal glands opening in a prominent, terminal blunt spinneret, half as wide as the tip of the tail. Females: Females are similar to males in most respects, in general longer. Amphids do not show dimorphism in shape or number of turns but in females they occupy just 36 % of the correspondent diameter, while in males this proportion is 45 %. Vulva at 54 % of the body; two perivulvar glands present, opening of perivulvar gland cells not clear; vagina transverse; ovejector sclerotized; vagina vera separated from vagina uterine by sphincter; uteri paired opposed; two cells (glands?) at the junction of vagina and uteri visible; spermatheca occupying about one third of each uterus; oviduct indistinct; ovaries antidromously reflexed, flexion at the junction of ovary and uterus. Anterior ovary to the left side of the intestine, posterior ovary to the right. Female tail conical, longer than in males. Terminal spinneret with same morphology than in males but slightly elongated. Juveniles: similar to adults in most morphological aspects. Differential diagnosis. Dystomanema cadizensis gen. nov. sp. nov. is characterized by its body size, number of supplements, both testes directed anteriorly and has the diagnostic features of the genus. The condition of both testes directed anteriorly was unknown within the family until now. Size of testes changes with male development but the posterior one always remains smaller than the anterior one. It is very close to Dystomanema brandtae gen. nov. sp. nov. but differs by the body size. Males about 70 % smaller than males of D. brandtae gen. nov. sp. nov. Among females this difference is reduced to about 40 %. The amount of precloacal supplements is also smaller: D. cadizensis gen. nov. sp. nov. has 10 to 12 cup-shape supplements while D. brandtae gen. nov. sp. nov. has 20. Etymology. The species is named after the sampling location ��� Gulf of C��diz. Dystomanema brandtae gen. nov. sp. nov. (Figs. 7 A���F, 8 A���F, 9 A���F, Table 1) Material examined. Two males and 3 females. Holotype male (Inventory No. UGMD 104269), paratype male (Inventory No. UGMD 104270), three paratypes females (Inventory No. UGMD 104271, 104272, 104273) Type habitat and locality. Remnant cold-seep sediments in the Larsen B area off the Eastern Antarctic Peninsula (65 �� 26.07 ������ 65 �� 26.10 ���S; 61 �� 26.48 ������ 61 �� 26.53 ���W) Description. Males: Body slender, long, uniform in diameter, tapering anteriorly and posteriorly. Fixation shape mostly coiled. Cuticle transversally striated with fine punctation more evident on the tail region. No lateral differentiation. Few somatic setae with no fixed distribution pattern. Head conical, low lips. Inner labial sensilla papilliform, six outer-labial short setiform sensilla, four cephalic setae 4 ��m or 25 % of corresponding body diameter long. Short dorso-sublateral subcephalic setae present. Amphid spiral 3 + turns. Oral opening ventrally displaced. Buccal cavity wide, deep (21 ��m), funnel shaped. Gymnostom followed by well-cuticularized pharyngostom with expanded conical posterior part. Sclerotized walls of pharyngostom with three small teeth, a dorsal tooth and two smaller subventral teeth. Pharynx cylindrical with a posterior muscular bulb. Nerve ring located about 20 % of pharynx length from anterior end. Secretory excretory pore located immediately after cephalic setae. Reproductive system with long vas deferens, with clear patch from the level of the 7 th to the 11 th and 5 th to the 10 th supplement from the cloaca. Anterior testis outstretched and anteriorly directed, posterior one smaller and reflexed. Anterior testis to the right of intestine and posterior one to the left. Spicules of equal size, about the same length as the cloacal diameter, slightly cephalated, bent about 1 / 3 of the distance from the distal end. Gubernaculum plate-like with a sclerotized rod-like internal structure at the distal half. Twenty conspicuous cup-shaped precloacal supplements with external longitudinal articulated flange. Prominent ventral precloacal spine anterior to the cloacal opening. Tail conical plump, with bluntly rounded tip. Three caudal glands opening in a terminal blunt spinneret. Females: Females are similar to males in most respects, in general longer. Amphids do not show dimorphism in shape or number of turns but in females amphids occupy just 40 % of the correspondent diameter, while in males this proportion is 50 %. Vulva at 53 % of the body; four perivulvar gland cells present; vagina transverse; ovejector without special sclerotization; vagina vera inconspicuous, no sphincter present; uteri paired opposed; spermatheca developed as outpocketing of each uterus; oviduct indistinct; ovaries antidromously reflexed, flexion at the junction of ovary and uterus; ovary position in relation to the intestine not clear. Female tail conical, longer than in males. Spinneret terminal, elongated. Juveniles: Similar to adults in most morphological aspects. Differential diagnosis. Dystomanema brandtae gen. nov. sp. nov. is characterized by its body size, number of supplements, posterior testis reflexed and has the diagnostic features of the genus. The posterior testis is smaller than the anterior one. The condition of reflexed posterior testis has not been mentioned for the family until now. However, the drawing of Filitonchus ewensis description (Platt, 1982), shows a similar situation as observed in D. brandtae gen. nov. sp. nov. but he does not mention it and just describes it as ���two opposed testes; anterior right, posterior left to the gut���. In addition, Lorenzen (1994) suggested that the posterior testis of Ethmolaimus (Family Ethmolaimidae, subfamily Ethmolaiminae) is reflexed by describing the position of the testis structure from his own observations: ���the posterior one (testis) proceeds anteriorly for a bit and then folds over to posterior���, although he doesn���t use the term ���reflexed���. These observations suggest that the occurrence of a reflexed posterior testis has been overlooked in the past, and may support the classification of Dystomanema gen. nov. within the family Ethmolaimidae. Dystomanema brandtae gen. nov. sp. nov. is very close to D. cadizensis gen. nov. sp. nov. but D. brandtae gen. nov. sp. nov. is about 70 % longer, this difference is reduced to 40 % when females of both species are compared. Unlike D. cadizensis gen. nov. sp. nov., the fixation shape of D.brandtae gen. nov. sp. nov. is mostly coiled. The punctation of D. brandtae gen. nov. sp. nov. remains fine but is more evident than in D. cadizensis gen. nov. sp. nov. Both species have very small teeth which can easily be overlooked, but in D. brandtae gen. nov. sp. nov. they are even smaller. D. brandtae gen. nov. sp. nov. has 20 cup-shaped supplements while D. cadizensis gen. nov. sp. nov. has 10 to 12. The clear patch of the vas deferens mentioned in the revision of Ethmolaimidae (Platt, 1982) is also recognized in the two new species of the new genus. A similar structure has been described by Gourbault and Vincx (1988) for Calomicrolaimus compridus Gerlach, 1956, although they mention ���there is a clear patch because of the presence of only very fine granules in that region (cf. some Ethmolaimidae, Platt 1982)���. In Dystomanema gen. nov. we didn���t find granules in this region. Muthumbi et al. (1997) also mention a clear patch for Sabatieria pisinna but do not explain if, like Gourbault and Vincx (1988), it is a region of very fine granules. The drawing of S. pisinna in the article doesn���t show the patch. Since the description of the patches in those other families does not match with the structures we identified in Dystomanema gen. nov., we are not able to affirm that the mentioned authors described the same type of structure. Etymology. The species is named in honour of Prof. Angelika Brandt, for her valuable contributions to Antarctic research., Published as part of Nara, Bezerra Tania, Ellen, Pape, Freija, Hauquier, Ann, Vanreusel & Jeroen, Ingels, 2013, New genus and two new species of the family Ethmolaimidae (Nematoda: Chromadorida), found in two different cold-seep environments, pp. 7-27 in Zootaxa 3692 (1) on pages 13-22, DOI: 10.11646/zootaxa.3692.1.4, http://zenodo.org/record/284259

Suborder Chromadorina Filipjev, 1929, Published as part of Nara, Bezerra Tania, Ellen, Pape, Freija, Hauquier, Ann, Vanreusel & Jeroen, Ingels, 2013, New genus and two new species of the family Ethmolaimidae (Nematoda: Chromadorida), found in two different cold-seep environments, pp. 7-27 in Zootaxa 3692 (1) on page 11, DOI: 10.11646/zootaxa.3692.1.4, http://zenodo.org/record/284259

Order Chromadorida Chitwood, 1933, Published as part of Nara, Bezerra Tania, Ellen, Pape, Freija, Hauquier, Ann, Vanreusel & Jeroen, Ingels, 2013, New genus and two new species of the family Ethmolaimidae (Nematoda: Chromadorida), found in two different cold-seep environments, pp. 7-27 in Zootaxa 3692 (1) on page 11, DOI: 10.11646/zootaxa.3692.1.4, http://zenodo.org/record/284259

Family Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 Diagnosis. Chromadoroidea. Characterized by an annulated cuticle bearing transverse rows of fine punctation, sometimes with lateral differentiation of fewer rows and rows of pores. Cephalic sensilla arranged in three circles of 6 + 6 + 4. Sensilla of the anterior circlet papilliform and both outer circlets setiform. Amphideal fovea uni- or multi-ventrally spiral. Buccal cavity with three equal teeth. Pharynx ending with a posterior muscular bulb of which the degree of development is correlated with the size of the dorsal tooth. Males have paired spicules of equal size and a slightly cuticularized rod-like gubernaculum. Conspicuous precloacal cup-shaped supplements with an external articulated flange are present as well as a ventral precloacal spine. Ovaries are paired, opposed, reflexed and of equal size; testes paired, laying on different sides of the intestine, the posterior one being smaller in most species. In most genera, the tail is conical, usually with a rounded tip (Platt, 1982; Jensen, 1994; Decraemer & Smol, 2006)., Published as part of Nara, Bezerra Tania, Ellen, Pape, Freija, Hauquier, Ann, Vanreusel & Jeroen, Ingels, 2013, New genus and two new species of the family Ethmolaimidae (Nematoda: Chromadorida), found in two different cold-seep environments, pp. 7-27 in Zootaxa 3692 (1) on page 11, DOI: 10.11646/zootaxa.3692.1.4, http://zenodo.org/record/284259

Subfamily Neotonchinae Wieser & Hopper, 1966 Diagnosis. Ethmolaimidae (originally Cyatholaimidae): buccal cavity elongate, depth greater than width; armed with very small to medium or large dorsal tooth located midway in the buccal cavity and with or without small subventral teeth. Cephalic sense organs 6 + 6 + 4. Pharynx with well-developed terminal bulb. Spicula of highly characteristic shape, proximal two-thirds fairly straight and nearly uniform thickness, distal third narrowed, cylindroid and with a slight S-shaped curvature. Precloacal supplements large, well-developed, cup-shaped. Tail plump, conoid, with bluntly rounded terminus. Marine. (Platt, 1982; Lorenzen 1994) (Type genus: Neotonchus Cobb, 1933) Genera belonging to Neotonchinae: Comesa Gerlach, 1956, Dystomanema gen. nov., Filitonchoides Jensen, 1985, Filitonchus Platt, 1982, Gomphionchus Platt, 1982, Gomphionema Wieser & Hopper, 1966, Nannolaimus Cobb, 1920, and Neothonchus Cobb, 1933. (Fig 3)

Mora, Camilo ... et al.-- 14 pages, 6 figures, 1 table, Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity. In contrast, only a small fraction of the world's ocean surface, mostly in polar regions, will experience increased oxygenation and productivity, while almost nowhere will there be ocean cooling or pH elevation. We compiled the global distribution of 32 marine habitats and biodiversity hotspots and found that they would all experience simultaneous exposure to changes in multiple biogeochemical variables. This superposition highlights the high risk for synergistic ecosystem responses, the suite of physiological adaptations needed to cope with future climate change, and the potential for reorganization of global biodiversity patterns. If co-occurring biogeochemical changes influence the delivery of ocean goods and services, then they could also have a considerable effect on human welfare. Approximately 470 to 870 million of the poorest people in the world rely heavily on the ocean for food, jobs, and revenues and live in countries that will be most affected by simultaneous changes in ocean biogeochemistry. These results highlight the high risk of degradation of marine ecosystems and associated human hardship expected in a future following current trends in anthropogenic greenhouse gas emissions. © 2013 Mora et al.

The Nazare Canyon on the Portuguese Margin (NE Atlantic) was sampled during spring-summer for three consecutive years (2005-2007), permitting the first inter-annual study of the meiofaunal communities at the Iberian Margin at two abyssal depths (similar to 3500 m and similar to 4400 m). Using new and already published data, the meiofauna standing stocks (abundance and biomass) and nematode structural and functional diversity were investigated in relation to the sediment biogeochemistry (e.g. organic carbon, nitrogen, chlorophyll a, phaeopigments) and grain size. A conspicuous increase in sand content from 2005 to 2006 and decrease of phytodetritus at both sites, suggested the occurrence of one or more physical disturbance events. Nematode standing stocks and trophic diversity decreased after these events, seemingly followed by a recovery/recolonisation period in 2007, which was strongly correlated with an increase in the quantity and bioavailability of phytodetrital organic matter supplied. Changes in meiofauna assemblages, however, also differed between stations, likely because of the contrasting hydrodynamic and food supply conditions. Higher meiofauna and nematode abundances, biomass and trophic complexity were found at the shallowest canyon station, where the quantity, quality and bioavailability of food material were higher than at the deeper site. The present results suggest that even though inter-annual variations in the sedimentary environment can regulate the meiofauna in the abyssal Nazare Canyon, heterogeneity between sampling locations in the canyon were more pronounced.

23 pages; International audience; In the Southern Ocean, that is areas south of the Polar Front, long-term oceanographic cooling, geographic separation, development of isolating current and wind systems, tectonic drift and fluctuation of ice sheets amongst others have resulted in a highly endemic benthic fauna, which is generally adapted to the long-lasting, relatively stable environmental conditions. The Southern Ocean benthic ecosystem has been subject to minimal direct anthropogenic impact (compared to elsewhere) and thus presents unique opportunities to study biodiversity and its responses to environmental change. Since the beginning of the century, research under the Census of Marine Life and International Polar Year initiatives, as well as Scientific Committee of Antarctic Research biology programmes, have considerably advanced our understanding of the Southern Ocean benthos. In this paper, we evaluate recent progress in Southern Ocean benthic research and identify priorities for future research. Intense efforts to sample and describe the benthic fauna, coupled with coordination of information in global databases, have greatly enhanced understanding of the biodiversity and biogeography of the region. Some habitats, such as chemosynthetic systems, have been sampled for the first time, while application of new technologies and methods are yielding new insights into ecosystem structure and function. These advances have also highlighted important research gaps, notably the likely consequences of climate change. In a time of potentially pivotal environmental change, one of the greatest challenges is to balance conservation with increasing demands on the Southern Ocean's natural resources and services. In this context, the characterization of Southern Ocean biodiversity is an urgent priority requiring timely and accurate species identifications, application of standardized sampling and reporting procedures, as well as cooperation between disciplines and nations.

The urge to understand spatial distributions of species and communities and their causative processes has continuously instigated the development and testing of conceptual models in spatial ecology. For the deep-sea, there is evidence that structure, diversity and function of benthic communities are regulated by a multitude of biotic and environmental processes that act in concert on different spatial scales, but the spatial patterns are poorly understood compared to those for other ecosystems. Deep-sea studies generally focus on very limited scale-ranges, thereby impairing our understanding of which spatial scales and associated processes are most important in driving diversity and ecosystem function of communities. Here, we used an extensive integrated dataset of free-living nematodes from deep-sea sediments to unravel which spatial scale is most important in determining benthic infauna communities. Multiple-factor multivariate permutational analyses were performed on different sets of community descriptors (structure, diversity, function, standing stock). The different spatial scales investigated cover two margins in the Northeast Atlantic, several submarine canyons/channel/slope areas, a bathymetrical range of 700–4300 m (represents different stations, 5–50 km apart), different sampling locations at each station (replication distances, 1–200 m), and vertical sediment profiles (cm layers). The results indicated that the most important spatial scale for diversity, functional and standing stock variability is the smallest one; infauna communities changed substantially more with differences between sediment depth layers than with differences associated to larger geographical or bathymetrical scales. Community structure differences were largest between stations at both margins. Important regulating ecosystem processes and the scale on which they occur are discussed. The results imply that, if we are to improve our understanding of ecosystem patterns of deep-sea infauna and the relevant processes driving their structure, diversity, function and standing stock, we must pay particular attention to the small-scale heterogeneity or patchiness and the causative mechanisms acting on that scale.

article i nfo Dispersal processes are known to influence dynamics of marine benthic communities. It has been argued that as a result of nematodes being small in size and lacking pelagic larvae, it is unlikely that they are able to dis- perse actively over wide geographical ranges. Nematode dispersal is therefore assumed to be predominantly driven by water currents entraining resuspended sediments containing nematodes. Three different types of substrates combined with sediment (algae, bacteria, and sulphides) and two different controls (empty and azoic sediment) were offered to a nematode community sinking through the water column in three indepen- dent, simultaneously running replicated experiments. Selective settlement of nematodes was observed whilst descending in the water column under ex-situ experimental conditions using samples collected in the Whittard canyon at 812 m of water depth. Significant differences in nematode community structure be- tween treatments suggest that different nematodes are attracted by different substrates. They may colonise suitable patches selectively when descending in the water column, but whether they are attracted by food or by other attractants, such as pheromones or other chemical signals, is still unclear. High abundances of the chemosynthetic, mouthless nematode Astomonema found in the canyon study area over medium-scale distances (10-100 m) contribute to the idea that resuspension events enable dispersal of nematodes over larger distances, after which active settlement can occur through chemical attraction.

Background: Recent climate-induced ice-shelf disintegration in the Larsen A (1995) and B (2002) areas along the Eastern Antarctic Peninsula formed a unique opportunity to assess sub-ice-shelf benthic community structure and led to the discovery of unexplored habitats, including a low-activity methane seep beneath the former Larsen B ice shelf. Since both limited particle sedimentation under previously permanent ice coverage and reduced cold-seep activity are likely toinfluence benthic meiofauna communities, we characterised the nematode assemblage of this low-activity cold seep and compared it with other, now seasonally ice-free, Larsen A and B stations and other Antarctic shelf areas (Weddell Sea and Drake Passage), as well as cold-seep ecosystems world-wide.Principal Findings: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance. Densities in the seep samples were high (.2000 individuals per 10 cm2) and showed below-surface maxima at a sediment depth of 2–3 cm in three out of four replicates. All samples were dominated by one species of the family Monhysteridae, which was identified as a Halomonhystera species that comprised between 80 and 86% of the total community. The combination of high densities, deeper density maxima and dominance of one species is shared by many cold-seep ecosystems world-wide and suggested a possible dependence upon a chemosynthetic food source. Yet stable 13C isotopic signals (ranging between 221.9760.86% and 224.8561.89%) were indicative of a phytoplankton-derived food source.Conclusion: The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity. The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.

The present study explored the selective feeding properties of Antarctic and Arctic deep-sea nematodes within an experimental setup. Nematodes are assumed to play an important role in the carbon flux within the polar bathyal food webs, but knowledge about their natural diets is limited. For the first time, deep-sea multicore sediment samples from both polar regions were incubated aboard research vessels with either 13C-labelled bacteria or diatoms to determine whether the nematode community prefers freshly settled phytodetritus to a bacterial food source. The cores were collected at 2112 to 2400 m water depth and incubated onboard for 1, 3 and 6 d in the Arctic (Hausgarten) and for 1, 7 and 14 d in Antarctica (Kapp Norvegia). Natural carbon isotope signals of nematodes and organic sedimentary carbon showed a clear average offset (+3.2‰). The contribution of bacteria to the diet of nematodes explained this 13C offset and observed natural 13C isotopic signatures. The nematodes showed a clear, relatively rapid (maximum at 6 to 7 d) and significant selective response to the pulse of 13C enriched bacteria in surface sediments of both regions. This indicated that bacteria were preferred over fresh phytoplankton as a carbon source for both Arctic and Antarctic deep-sea nematode communities. The results also suggest that bacteria may provide a path through which unused detritus may enter the traditional metazoan food web by microbial reworking of organic matter. At the same time, uptake rates of nematode communities were minimal, which suggests the contribution of nematodes to benthic mineralisation of freshly deposited organic matter may be limited in deep polar seas.