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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.

Microplastic (MP) pollution is an ongoing problem in coastal systems, where wastewater treatment plants (WWTPs) deposit particles daily. This study examined MP characteristics at WWTP outflow and control sites in St. Andrew Bay in Northwestern Florida, USA. WWTP sites contained mostly polypropylene fragments (180.1 μm avg. size), while reference sites contained polypropylene fragments, and polyethylene and polyester fibers (315.3 μm avg. size). MP sizes were strongly linked to distance from the nearest WWTP, while shape and polymer compositions were more closely related to dissolved oxygen concentrations and distance to the nearest water input source. The prevalence of polypropylene fragments at WWTP sites suggests that extreme weather events during the study flushed land-based debris into the system, where it was buried in the sediments. Increased abundances of polyester and polyethylene terephthalate in the winter at WWTP sites are indicative of the role that laundering synthetic textiles plays in coastal MP pollution.

Recent studies have increased the known diversity and distribution of kinorhynchs in the Gulf of Mexico. For this study, sediment was sampled from Alabama coastal waters at shallow depths ranging f...

Wastewater treatment plants (WWTPs) cause approximately 25 % of microplastics (MPs) in the marine environment. While research on MPs in WWTP effluent has demonstrated that an abundance of particles enter the marine environment, little effort has gone to assessing MP abundances in coastal sediments to determine their seasonal and spatial variability. Here, we assessed MP abundances in sediments at sites of WWTP outflow and at non-polluted sites over six consecutive seasons within the St. Andrew Bay system in Northwestern Florida. We showed that MP abundances were highest at one of the WWTP sites, where they increased with increasing distance away from the input source (3.16 ± 1.59 MP/kg to 34.03 ± 11.69 MP/kg sediment dry weight). We also found that mean MP abundances were highest in the winter (12.41 ± 3.56 MPs/kg sediment dry weight) and lowest in the spring (2.17 ± 0.63 MPs/kg sediment dry weight). Therefore, while WWTPs differentially retain MPs in their removal processes, MP pollution in the St. Andrew Bay system shows seasonal dynamics like other studies. Although average MP abundance in surface sediments (0-5 cm) was higher than in subsurface sediments (5-10 cm) at all sites, this difference was not as substantial as has been found in other studies. Based on mean MP abundance in surface sediments, we estimate that there are 30 billion MPs within the surface layer of sediment in the St. Andrew Bay system, and that the particles export to the Gulf of Mexico because of seasonal flushing between the winter and spring. The distributions of MPs in the system were also likely driven by extreme weather events that occurred in the bay system during 2018 and 2020, which acts as a cautionary tale for coastal urban ecosystems in the face of sea level rise and climate change.

Free Ocean CO2 Enrichment (FOCE) experiments are a relatively recent development in ocean acidification research, designed to address the need for in situ, long-term, community level experiments. FOCE studies have been conducted across different marine benthic habitats and regions, from Antarctica to the tropics. Based on this previous research we have formed some core operating principles that will aid those embarking on future FOCE experiments. FOCE studies have potential to provide important insight into the effects of ocean acidification that can add to or refine conclusions drawn from laboratory or single species studies because they are conducted in situ on intact assemblages. Scaling up from sub-organismal and individual effects to also include indirect impacts on the ecosystem and ecosystem services, make FOCE experiments essential in filling in current knowledge gaps in our understanding of ocean acidification. While FOCE systems are complex, relatively costly, and somewhat difficult to operate, the challenges they pose are tractable and they have proven to be a useful approach in ocean acidification research. The aim of this paper is to draw from the experiences of past FOCE experiments and provide practical advice for designing, building and operating a FOCE experiment. Some of the most important recommendations include: field testing the system design; having a backup power supply; using replicate treatment enclosures; monitoring and maintaining the chemistry appropriately; allowing sufficient time to achieve near CO2 equilibrium conditions; and having a scientific focus with a core set of hypotheses. Future FOCE experiments could focus on longer durations, multiple factors, and testing more intact benthic marine communities and ecosystems. We hope this paper will encourage further FOCE deployments and experiments, as well as provide some guidelines to improve future FOCE studies and advance ocean acidification research.

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 (

Biological communities beneath Antarctic ice shelves remain a mystery, hampering assessment of ecosystem development after ice-shelf collapse. Here we highlight major gaps in understanding of the patterns and processes in these areas, and suggest effective ways to study the ecological impacts of ice-shelf loss under climate change.

Sedimentary habitats cover most of the ocean bottom and therefore constitute the largest single ecosystem on Earth in spatial coverage. The benthic ecosystem contributes to human well-being by providing essential services such as food production and nutrient cycling. Although meiofauna are well-recognised as an abundant and ubiquitous component of benthic communities, empirical evidence of their wider role in marine ecosystems is scattered across the literature. Some ecologists and decision-makers thus remain sceptical about what meiofauna can tell them about the provision of ecosystem services. This article investigates empirical evidence on the roles of meiofauna in benthic ecosystems using a conceptual model that links the supply of an ecosystem service, the ecosystem processes that contribute to that service (e.g. production, consumption and decomposition of organic matter, nutrient regeneration, and energy transfer to higher trophic levels) and the meiofaunal activities (e.g. bioturbation and feeding) that regulate these processes. Meiofauna activities modify a series of physical, chemical and biological sediment properties. They often do so simultaneously by, for example, displacing sediment grains during burrow construction and displacing organic matter and microorganisms within the sediment matrix during feeding. These modifications directly and indirectly, positively and negatively affect various ecosystem services including sediment stabilisation, biochemical cycling, waste removal and food web dynamics, at various spatial and temporal scales. Meiofauna can mediate ecosystem processes in sediments with little or no macrofauna, thereby increasing the resilience of those benthic ecosystem processes that are essential for the continued delivery of ecosystem services desired by society. This is of growing importance since benthic ecosystems are under increasing anthropogenic pressure. Whilst studies over the past five decades have emphasised the important roles meiofauna play in benthic ecosystems, future studies will need to determine how consistent and widespread these roles are.

Although nematodes are the most abundant metazoans in marine environments and present an important biological and ecological model organism to assess marine ecosystem processes and functions, there are in fact very few studies that use nematodes to investigate ecological communities and relationships on “mobile” ecosystems. Arguably one of the most mobile or dynamic marine ecosystems is a sea turtle carapace , hosting tens to hundreds or even thousands of epibiotic organisms; and as the turtle breeds, feeds and migrates, provides an ecosystem that is continuously exposed to changes and potential colonizers. In this study we investigated the nematode communities associated with 19 Hawksbill sea turtle carapaces ( Eretmochelys imbricata) , and compared nematode structural (composition, richness and diversity) and functional (trophic types and gender/life stages) community parameters with those of other comparable epibiotic substrates (macrophytes, natural and artificial hard substrates) to see whether turtle carapaces are hotspots of nematode diversity and function among substrates suitable for epifauna . We also addressed potential epibiotic macrofauna-nematode interactions by looking at the relationships between macrofauna richness and nematode richness, diversity and community composition. Results suggest that the macrofauna play a bioconstructing role, creating several microenvironments, and thereby enhancing the richness and diversity of the associated nematode assemblages. This was supported by a direct and positive relationship between macrofauna and nematode richness, and implies a genera enrichment process across size classes and phyla. All heterotrophic nematode feeding guilds were recovered from the carapaces, with dominance of predators/omnivores and epistrate feeders. Nematode juveniles dominated in terms of abundance, and a female/male ratio of 1.11 was observed. Nematode richness and diversity were higher than found on other substrates, but feeding guild, gender and life stage structure did not differ compared to nematode communities from all other epibiotic substrates. As a result, we argue that turtle carapaces can be seen as hotspots for nematode biodiversity compared to other epibiotic substrates, but this is not reflected in the function of the nematode community. This study is the first to investigate in detail sea turtle carapace nematode communities, their richness, diversity, trophic and life cycle structure, and potential interactions with their co-epibionts, the macrofauna.

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.

The effects of hydrocarbons in marine sediments on Antarctic meiofaunal communities (nematodes and copepods) were investigated in a five year field experiment at Casey Station, East Antarctica. The effects of four different types of hydrocarbons were examined: clean mineral lube oil, used mineral lube oil, synthetic lube oil marketed as being rapidly biodegradable, and diesel fuel (Special Antarctic Blend). Sediments were sieved to remove macrofauna and then treated with one of the oils, then deployed in trays on the seabed (12–18 m) under sea ice, along with control, uncontaminated sediment. Samples of the meiofaunal communities were collected at one, two and five years and nematodes identified to genus and copepods to family. There were significant differences between meiofaunal communities in hydrocarbon-treated sediment compared to controls, but each hydrocarbon type had quite different effects. Effects persisted to five years and communities showed no signs of recovery or becoming more similar to controls. Nematodes were more sensitive to hydrocarbons than copepods, showing very distinct community differences between different treatments which persisted over the five years. In contrast, copepod communities showed less distinct, more variable changes, which decreased in severity over five years. Nematode abundance initially decreased in hydrocarbon treatments in comparison to controls, except for the biodegradable oil treatment, and this persisted also over five years. In contrast, copepod abundance initially increased in hydrocarbon treatments compared to controls, and then declined, and by five years abundances were lower in hydrocarbon treatments than in controls. Whilst structural community, abundance and diversity differences for nematodes and copepods remained after 5 years, the nematode functional parameters based on feeding types and maturity characteristics showed a substantial degree of recovery after 5 years, suggesting some functional recovery of the nematode community. This experiment demonstrates that different hydrocarbons can have very different effects on sediment meiofauna and that despite strong patterns of community effects it was very difficult to characterize effects on different taxa. The effects of oils in sediments are also likely to persist for periods greater than five years and could take decades to recover.

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.

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).

The study of meiofauna, the motile microscopic fauna of aquatic sediments, is increasingly appreciated in modern aquatic ecology. This special issue includes invited and selected papers presented at the 16 th International Meiofauna Conference in Heraklion, Crete, Greece between 3 rd and 8 th July 2016. The collection of papers presents some of the most recent and exciting advances in meiobenthology. It offers insights into potential limitations as well as opportunities for meiobenthic studies and reflects on the challenges which lie ahead for future research endeavors in the field.

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.

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.

Due to the impacts of natural processes and anthropogenic activities, different coastal wetlands are faced with variable patterns of heavy metal contamination. It is important to quantify the contributions of pollutant sources, in order to adopt appropriate protection measures for local ecosystems. The aim of this research was to compare the heavy metal contamination patterns of two contrasting coastal wetlands in eastern China. In addition, the contributions from various metal sources were identified and quantified, and influencing factors, such as the role of the plant Spartina alterniflora, were evaluated. Sediment samples were taken from two coastal wetlands (plain-type tidal flat at the Rudong (RD) wetland vs embayment-type tidal flat at Luoyuan Bay (LY)) to measure the content of Al, Fe, Co, Cr, Cu, Mn, Mo, Ni, Sr, Zn, Pb, Cd, and As. Inductively coupled plasma atomic emission spectrometry, flame atomic absorption spectrometry, and atomic fluorescence spectrometry methods were used for metal detection. Meanwhile, the enrichment factor and geoaccumulation index were applied to assess the pollution level. Principle component analysis and receptor modeling were used to quantify the sources of heavy metals. Marked differences in metal distribution patterns between the two systems were present. Metal contents in LY were higher than those in RD, except for Sr and Mo. The growth status of S. alterniflora influenced metal accumulations in RD, i.e., heavy metals were more easily adsorbed in the sediment in the following sequence: Cu > Cd > Zn > Cr > Al > Pb ≥ Ni ≥ Co > Fe > Sr ≥ Mn > As > Mo as a result of the presence and size of the vegetation. However, this phenomenon was not observed in LY. A higher potential ecological risk was associated with LY, compared with RD, except for Mo. Based on a receptor model output, sedimentary heavy metal contents at RD were jointly influenced by natural sedimentary processes and anthropogenic activities, whereas they were dominated by anthropogenic activities at LY. A combination of geochemical analysis and modeling approaches was used to quantify the different types of natural and anthropogenic contributions to heavy metal contamination, which is useful for pollution assessments. The application of this approach reveals that natural and anthropogenic processes have different influences on the delivery and retention of metals at the two contrasting coastal wetlands. In addition, the presence and size of S. alterniflora can influence the level of metal contamination in sedimentary environments.

In the near future, the marine environment is likely to be subjected to simultaneous increases in temperature and decreased pH. The potential effects of these changes on intertidal, meiofaunal assemblages were investigated using a mesocosm experiment. Artificial Substrate Units containing meiofauna from the extreme low intertidal zone were exposed for 60 days to eight experimental treatments (four replicates for each treatment) comprising four pH levels: 8.0 (ambient control), 7.7 & 7.3 (predicted changes associated with ocean acidification), and 6.7 (CO2 point-source leakage from geological storage), crossed with two temperatures: 12 °C (ambient control) and 16 °C (predicted). Community structure, measured using major meiofauna taxa was significantly affected by pH and temperature. Copepods and copepodites showed the greatest decline in abundance in response to low pH and elevated temperature. Nematodes increased in abundance in response to low pH and temperature rise, possibly caused by decreased predation and competition for food owing to the declining macrofauna density. Nematode species composition changed significantly between the different treatments, and was affected by both seawater acidification and warming. Estimated nematode species diversity, species evenness, and the maturity index, were substantially lower at 16 °C, whereas trophic diversity was slightly higher at 16 °C except at pH 6.7. This study has demonstrated that the combination of elevated levels of CO2 and ocean warming may have substantial effects on structural and functional characteristics of meiofaunal and nematode communities, and that single stressor experiments are unlikely to encompass the complexity of abiotic and biotic interactions. At the same time, ecological interactions may lead to complex community responses to pH and temperature changes in the interstitial environment.

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).

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high-, mid- and low-water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community-wide metric approach based on taxon-specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high- and mid-water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community-wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem.

Diverse assemblages of infauna in sediments provide important physical and biogeochemical services, but are under increasing pressure by anthropogenic activities, such as benthic trawling. It is known that trawling disturbance has a substantial effect on the larger benthic fauna, with reductions in density and diversity, and changes in community structure, benthic biomass, production, and bioturbation and biogeochemical processes. Largely unknown, however, are the mechanisms by which the trawling impacts on the large benthic macro- and megafauna may influence the smaller meiofauna. To investigate this, a mesocosm experiment was conducted whereby benthic nematode communities from a non-trawled area were exposed to three different densities (absent, low, normal) of 7 large (> 10 mm) naturally co-occurring, bioturbating species which are potentially vulnerable to trawling disturbance. The results showed that total abundances of nematodes were lower if these large macrofauna species were present, but no clear nematode abundance effects could be assigned to the macrofauna density differences. Nematode community structure changed in response to macrofauna presence and density, mainly as a result of the reduced abundance of a few dominant nematode species. Any detectable effects seemed similar for nearly all macrofauna species treatments, supporting the idea that there may be a general indirect, macrofauna-mediated trawling impact on nematode communities. Explanations for these results may be, firstly, competition for food resources, resulting in spatial segregation of the meio- and macrobenthic components. Secondly, different densities of large macrofauna organisms may affect the nematode community structure through different intensities of bioturbatory disturbance or resource competition. These results suggest that removal or reduced densities of larger macrofauna species as a result of trawling disturbance may lead to increased nematode abundance and hints at the validity of interference competition between large macrofauna organisms and the smaller meiofauna, and the energy equivalence hypothesis, where a trade-off is observed between groups of organisms that are dependent on a common source of energy.