The time-integrated expression of δ13C and δ15N in components (leaves, stems, and roots) and associated biota in native and planted mangrove forests in the Central Arabian Gulf (CAG) was assessed to evaluate the forests’ functional responses to environmental extremes. Both mangroves and associated biota at the planted mangroves exhibited isotopic signatures that differed markedly from those of native stands. The native mangrove forests had lower δ13C (− 27.6 ± 0.4) and higher δ15N (0.8 ± 0.7) ratios than those that had been planted (− 24.5 ± 0.6 and − 3.8 ± 0.7, respectively). The leaves, stems, and roots at the planted sites showed about ∼3‰ higher δ13C and lower δ15N values compared to native plants. Similarly, macroalgae exhibited a comparable trend, with δ13C about 1.5–3‰ and δ15N values ∼ 3–6‰ lower at the planted site compared to native stands, with the strongest δ15N depletion observed at extreme salinities (55). This pronounced δ15N depletion suggests nitrogen limitation and potential alteration in nitrogen cycling processes under elevated salinity. The effects of extreme climatic conditions limit resource acquisition and overall plant performance in the Gulf. A high sediment δ13C (− 16.6 ± 1.0) and low carbon:nitrogen ratio (7.7 ± 3.7) in natural forests reflect enriched organic matter from a diverse variety of sources, including benthic microphytes. Our findings suggest that the ecological services provided by the mangrove planted four decades ago are likely inferior to those of natural forest. Policymakers and restoration programs concerned with the conservation of mangrove forests should consider the relative trade-offs of deforesting of ‘old’ growth forests for urban development versus the limited potential of afforestation on barren beaches.

Impacts of the exceptionally high temperature and salinity on species composition, abundance, biomass and diversity of zooplankton communities were examined in the central Arabian (Persian) Gulf in late winter and summer of 2010 and 2011. Remarkably diverse zooplankton assemblages were characterized with small calanoids (Paracalanus aculeatus and Temora longicornis), cyclopoids (Oithona nana, Oithona plumifera, Corycaeus flaccus and Corycaeus lautus) and harpacticoids (Euterpina acutifrons) with relatively low abundance and biomass. Overall, the low biomass and abundance were not significantly associated with phytoplankton, whereas zooplankton faunal similarities were significantly correlated with water properties measured as environmental distances across sampling sites. Spatially, the lowest abundance, biomass and diversity occurred in extremely saline nearshore waters off the western Qatar peninsula, whereas the highest abundance, biomass and diversity consistently appeared at northeast offshore locations that periodically encounter nutrient and species-rich but low-salinity water entering the Arabian Gulf via the Strait of Hormuz. Numerically, the relative dominance of calanoids along with lower salinity and high chlorophyll-a concentration in the northeast Arabian Gulf implies that zooplankton populations are likely replenished by the seasonal (summer) transport of species from the Gulf of Oman and the Arabian Sea, which may explain partly the high variations of species richness and zooplankton abundance previously reported in the region. Given increasing evidence of climate-change induced responses of zooplankton, our findings suggest that in the semi-closed Arabian Gulf resident populations stressed by the harsh environment are likely to continue to be sustained only by invading water masses during the summer.

Amphipod crustacean diversity and zonation are described from the large Mississippi Canyon that extends from the continental shelf across the entire continental margin. Benthic amphipods were sampled on four cruises from 2000 to 2004 from six locations in the Mississippi Canyon from depths of 480 through 2,750 m, and compared with five locations in a second transect on the open continental slope approximately 100 km west of the canyon to assess the canyon effect on the structure and composition of amphipod assemblages. Five replicates were collected from each location using 0.2 m –2 GOMEX box corer. Amphipods amounted to 40% of the total faunal abundance within the canyon compared to only 4% in the non-canyon samples. Of the seventy-two species (19 families) collected, 61 were encountered in the canyon compared to 38 on the non-canyon transect. The trough-like head of the canyon (480 m) supported high densities (4,446–26,933 ind./m 2 ) of the filter feeding, tube dwelling ampeliscid amphipod ( Ampelisca mississippiana ), the highest densities sampled compared to any other single species, at any other location, either within or outside the canyon, reflecting extreme flux of organic detritus from the continental shelf. The dominance by this single species suppressed the within – habitat (alpha) diversity and evenness, compared to relatively high diversity within the 1,000–1,500 m depths interval both in and outside the canyon. The species richness and alpha diversity exhibited mid-depth maxima at ca. 1,100 m both in and out of the canyon. High species richness (61) over the entire length of the canyon is presumed to be a function of greater topographic complexity and intermittent mass wasting of sediment down the canyon axis. The absence of nestedness is attributed to the amphipod reproductive pattern that lacks dispersive larval stages and brooding comparatively small numbers of eggs in this taxon. Despite depressed diversity at the head of the canyon, the fact that the number of amphipod species in the Mississippi Canyon was 1.5 times their numbers on the adjacent slope suggests that this physiographic feature enriches geographic-scale species diversity.

There is a paucity of information on the levels of PAHs and PCBs in the deep-sea (>= 200 m). In this study, the body-burdens of 16 PAHs and 29 PCBs were measured in: Actinaria (sea anemones), Holothumidea (sea cucumber), Pennatulacea (sea pens), and Crinoidea (sea lilies) in the deep Gulf of Mexico. All epibenthic species were collected at depths of approximately 2000 m. The PAH and PCB congener profile displayed a similar pattern of bioaccumulation across all four taxa. The high molecular weight PAH, dibenz[a,h]anthracene, was the most abundant PAH in all organisms, ranging from 36 to 53% of sum total PAHs. PCBs 101 and 138 exhibited the highest levels at 20-25% of total congener concentrations in all taxa. The exposure to PAHs and PCBs is likely attributed to contaminated particulate organic matter that is consumed by the deposit and filter feeding epibenthic megafauna sampled in this study.

Abundance, alpha diversity, and faunal zonation of infaunal bivalve mollusks were measured along multiple depth transects in the deep northern Gulf of Mexico (GoM) covering depths of 213 to 3,732 m. Density decreased exponentially from the shallow continental slope (0.2-1.0 km) down to the abyssal plain depths (3.0-3.7 km). Diversity increased down the slope to a maximum at intermediate depths (1.2 to 1.8 km), followed by a decrease down to the Sigsbee Deep. The maximum diversities coincided with an organic carbon input of 10 to 16.3 mg C m(-2) d(-1), whereas the minimum was encountered at the high (ca. 52-78 mg C m(-2) d(-1)) and low extremes (ca. 3-5 mg C m(-2) d(-1)) of the detrital food input. Seven faunal zones could be identified on the basis of species composition with faunal changes being more abrupt on the upper slope compared to the lower slope and abyssal plain, possibly due to steeper gradients in physical variables.

Animal migrations are of global ecological significance, providing mechanisms for the transport of nutrients and energy between distant locations. In much of the deep sea (>200 m water depth), the export of nutrients from the surface ocean provides a crucial but seasonally variable energy source to seafloor ecosystems. Seasonal faunal migrations have been hypothesized to occur on the deep seafloor as a result, but have not been documented. Here, we analyse a 7.5-year record of photographic data from the Deep-ocean Environmental Long-term Observatory Systems seafloor observatories to determine whether there was evidence of seasonal (intra-annual) migratory behaviours in a deep-sea fish assemblage on the West African margin and, if so, identify potential cues for the behaviour. Our findings demonstrate a correlation between intra-annual changes in demersal fish abundance at 1,400 m depth and satellite-derived estimates of primary production off the coast of Angola. Highest fish abundances were observed in late November with a smaller peak in June, occurring approximately 4 months after corresponding peaks in primary production. Observed changes in fish abundance occurred too rapidly to be explained by recruitment or mortality, and must therefore have a behavioural driver. Given the recurrent patterns observed, and the established importance of bottom-up trophic structuring in deep-sea ecosystems, we hypothesize that a large fraction of the fish assemblage may conduct seasonal migrations in this region, and propose seasonal variability in surface ocean primary production as a plausible cause. Such trophic control could lead to changes in the abundance of fishes across the seafloor by affecting secondary production of prey species and/or carrion availability for example. In summary, we present the first evidence for seasonally recurring patterns in deep-sea demersal fish abundances over a 7-year period, and demonstrate a previously unobserved level of dynamism in the deep sea, potentially mirroring the great migrations so well characterized in terrestrial systems.

The cycling and fate of polycyclic aromatic hydrocarbons (PAHs) is not well understood in estuarine systems. It is critical now more than ever given the increased ecosystem pressures on these critical coastal habitats. A budget of PAHs and cycling has been created for Galveston Bay (Texas) in the northwestern Gulf of Mexico, an estuary surrounded by 30-50% of the US capacity of oil refineries and chemical industry. We estimate that approximately 3 to 4 mt per year of pyrogenic PAHs are introduced to Galveston Bay via gaseous exchange from the atmosphere (ca. 2 mt/year) in addition to numerous spills of petrogenic PAHs from oil and gas operations (ca. 1.0 to 1.9 mt/year). PAHs are cycled through and stored in the biota, and ca. 20 to 30% of the total (0.8 to 1.5 mt per year) are estimated to be buried in the sediments. Oysters concentrate PAHs to levels above their surroundings (water and sediments) and contain substantially greater concentrations than other fish catch (shrimp, blue crabs and fin fish). Smaller organisms (infaunal invertebrates, phytoplankton and zooplankton) might also retain a significant fraction of the total, but direct evidence for this is lacking. The amount of PAHs delivered to humans in seafood, based on reported landings, is trivially small compared to the total inputs, sediment accumulation and other possible fates (metabolic remineralization, export in tides, etc.), which remain poorly known. The generally higher concentrations in biota from Galveston Bay compared to other coastal habitats can be attributed to both intermittent spills of gas and oil and the bay's close proximity to high production of pyrogenic PAHs within the urban industrial complex of the city of Houston as well as periodic flood events that transport PAHs from land surfaces to the Bay.

Coastal ocean productivity is often dependent on riverine sources of nutrients, yet it can be difficult to determine how far the influence of the river extends. The northern Gulf of Mexico (GOM) receives freshwater and nutrients discharged mainly from the Mississippi and Atchafalaya Rivers. We used nutrient/salinity relationships to (i) differentiate the nutrient inputs of the two rivers and (ii) determine the potential extent of the zones where productivity is affected by each. We identified three different zones: one close to the coast having a linear nutrient/salinity relationship where physical forcing (river flow) dominates, one offshore with nutrient (N or Si) concentrations <1 mu M, and one between them with variable nutrient concentrations largely controlled by consumption by autotrophs. While in the GOM salinity/nutrient relationships varied systematically with distance from the two rivers in winter, this was not seen in summer. Thus, the methodology is not always applicable directly, because the boundaries of the different regions vary with river flow, overall nutrient flux, and grids of stations at the regional spatial scale (15-20 km in the GOM), rather than single sections are needed to determine boundaries.

The coastal Gulf of Mexico (GOM) and coastal sea off the Korean Peninsula (CSK) both suffer from human-induced eutrophication. We used a nitrogen (N) mass balance model in two different regions with different nitrogen input sources to estimate organic carbon fluxes and predict future carbon fluxes under different model scenarios. The coastal GOM receives nitrogen predominantly from the Mississippi and Atchafalaya rivers and atmospheric nitrogen deposition is only a minor component in this region. In the CSK, groundwater and atmospheric nitrogen deposition are more important controlling factors. Our model includes the fluxes of nitrogen to the ocean from the atmosphere, groundwater and rivers, based on observational and literature data, and identifies three zones (brown, green and blue waters) in the coastal GOM and CSK with different productivity and carbon fluxes. Based on our model results, the potential primary production rate in the inner (brown water) zone are over 2 gC m−2 d−1 (GOM) and 1.5 gC m−2 d−1 (CSK). In the middle (green water) zone, potential production is from 0.1 to 2 (GOM) and 0.3 to 1.5 gC m−2 d−1 (CSK). In the offshore (blue water) zone, productivity is less than 0.1 (GOM) and 0.3 (CSK) gC m−2 d−1. Through our model scenario results, overall oxygen demand in the GOM will increase approximately 21 % if we fail to reduce riverine N input, likely increasing considerably the area affected by hypoxia. Comparing the results from the USA with those from the Korean Peninsula shows the importance of considering both riverine and atmospheric inputs of nitrogen. This has direct implications for investigating how changes in energy technologies can lead to changes in the production of various atmospheric contaminants that affect air quality, climate and the health of local populations.

The α-diversity in two large-scale, systematic macrobenthos surveys (1983–1985 and 2000–2001) in the deep northern Gulf of Mexico (GoM) has been compared under strong vertical and horizontal productivity gradients to examine underlying factors that control the distribution of deep-sea diversity. We calculated the effective numbers of equally abundant species (Hill numbers) from 100 randomly selected individuals to examine spatial patterns of species richness and evenness. Macrofauna α-diversity was a negative parabolic function of depth; the minima occurred at high export POC flux on the upper continental slope and on the abyssal plain with extremely low input of POC; the maximum occurred at intermediate levels of macrofauna biomass and input of POC. The overall parabolic pattern of α-diversity was stable over the 20-year period and not statistically different between meso-scale depressions (e.g., basins and canyons) and their adjacent slope habitats; however, the diversity was significantly higher in the NE than the NW slope habitats. The observed Mid-Depth-Maximum (MDM) in α-diversity, we suggest, was likely a result of dynamic equilibrium between productivity and competitive exclusion. The higher diversity and productivity in the NE than the NW GoM at similar depth ranges suggests that, for the first time, the productivity-diversity relationship was observed independent of other depth-related factors. The findings provide a foundation for predicting the possible responses of diversity to climate change and anthropogenic impacts in the deep sea.

The Deep Gulf of Mexico Benthos (DGoMB) program was designed to determine patterns of abundance and diversity of meiofauna and macrofauna in the northern Gulf of Mexico continental slope between 300 m and 3700 m depth. Abundance of all taxa was significantly influenced by the particulate organic carbon (POC) flux. The abundance of meiofauna, macrofauna, crustaceans, and mollusks increased with increasing clay content, but clay had no significant effect on harpacticoid or polychaete abundance. Polychaete diversity was significantly correlated to POC flux, but mollusk diversity was correlated to sediment properties. Polychaetes had the highest average abundance and species richness. Harpacticoids were the least abundant of the four taxa, but had the highest values of Hill’s diversity index and Pielou’s evenness index. Harpacticoids and Crustaceans had high species turnover rates, resulting in low similarities of the respective faunas between sampling stations, whereas mollusks and polychaetes were more similar between different sampling stations. Overall, there were interannual differences in abundance patterns of meiofauna and macrofauna, similar community structure patterns among the taxa, and unique distributions of diversity with respect to depth and longitude.

When the Deepwater Horizon oil rig blew out in 2010, the immediate threats to productive deep water and estuarial fisheries and the region's fishing and energy economies were obvious. Less immediately obvious, but equally unsettling, were risks to human health posed by potential damage to the regional food web. This paper describes grassroots and regional efforts by the Gulf Coast Health Alliance: health risks related to the Macondo Spill Fishermen's Citizen Science Network project. Using a community-based participatory research approach and a citizen science structure, the multiyear project measured exposure to petrogenic polycyclic aromatic hydrocarbons, researched the toxicity of these polycyclic aromatic hydrocarbon compounds, and communicated project findings and seafood consumption guidelines throughout the region (coastal Louisiana, Mississippi, and Alabama). Description/analysis focuses primarily on the process of building a network of working fishermen and developing group environmental health literacy competencies.

: This report presents data obtained from cored sediments collected during numerous cruises in the Northwest Atlantic area. The cores were obtained by SCUBA, gravity cores and DSRV ALVIN. The sediments were sampled with 6 centimeter diameter plastic core liners and ranged in length from 9 to 63 centimeters. Analyses conducted on sediment material include organic carbon, organic nitrogen, percent sand-silt-clay, percent calcium carbonate and pore water concentrations of ammonia, nitrite, nitrate, silicate and phosphate. (Author)

The Deepwater Horizon (DWH) explosion in 2010 is the largest oil spill (Macondo) in U.S. history. We focused on gaining an understanding of the physical health and mental health effects attributable to the Macondo oil spill. This is a report of a cross-sectional cohort study (wave 1) to establish baseline' findings and meant to provide descriptive information to be used for a multi-wave, longitudinal study. Gulf Coast Health Alliance: health Risks related to the Macondo Spill (GC-HARMS) uses a Community-Based Participatory Research approach, thus including multi-disciplinary, multi-institutional academic partners and representatives of three communities impacted by the spill. Three research sites were selected for human sampling along the Gulf of Mexico coast including two from Mississippi and one from Louisiana, with Galveston, Texas, serving as a comparison site, given that it was not directly impacted by the spill. One hundred participants were selected from each community, representing adults, seniors and children, with approximately equal numbers of males and females in each group. Participants completed initial assessments including completion of a baseline' survey and, rigorous physical assessments. Results from wave 1 data collection reported herein reveal changes in self-reported physical health and mental health status following the oil spill, disparities in access to healthcare, and associations between mental health and emotional conditions related to displacement/unemployment. Few environmental health studies have been conducted in communities impacted by significant oil spills. Results imply potential prolonged effects on mental health and community vulnerability.

AimTo test the hypothesis that low productivity drives the nestedness component of -diversity in polychaetes at the deep-sea floor.LocationWestern Gulf of Mexico.MethodsWe used A. Baselga's (2010, Global Ecology and Biogeography, 19, 134-143) metrics of species replacement and nestedness to assess their overall significance with differences in depth and particulate organic carbon (POC) flux to the seafloor. We used M. A. Rodriguez-Girones & L. Santamaria's (2006, Journal of Biogeography, 33, 924-935) BINMATNEST to calculate the significance and direction of nestedness with depth and POC flux.ResultsNestedness was the most significant part of -diversity with depth and POC flux. The rank order of nestedness increased significantly with increasing depth, and decreased significantly with increasing POC flux. There was little endemism below 2000m.Main conclusionThe polychaete fauna in the deepest western Gulf of Mexico is largely a nested subset of the shallower upper to mid-bathyal fauna. While the causes of -diversity in the deep sea are undoubtedly multivariate, the relative importance of turnover and nestedness appears to be modulated by productivity in the form of POC flux to the seafloor. Under circumstances of extremely low POC flux and animal density in the deepest reaches of the Gulf, nestedness may be caused by some populations being maintained by immigration from larger populations upslope, or by biogeographic filtering for tolerance to abyssal conditions. Resources at great depths in regions of exceptionally low productivity may be too limited to permit adaptation resulting in endemism and continued downslope turnover. If productivity helps to explain the nestedness part of -diversity, this may lead to a more unified theory of deep-sea biodiversity.

Ecosystem components at the bottom of oceanic food webs (phytoplankton, zooplankton, mid-water fishes, and seafloor organisms) are tabulated and mapped. Sessile communities in hard bottom habitats, including the Flower Garden Banks National Marine Sanctuary, are also reviewed. Some of the foundation species have symbiotic bacteria that use methane as a source of energy and carbon, but others (the vestimentiferan worms) use sulfide for energy. The inner continental shelf habitats are supplied with nutrients from numerous rivers, and thus, the biota nearshore is supported by phytoplankton enriched in nitrate. The freshwater and nitrate supplied to the Louisiana coast by the Mississippi River are so large that they overwhelm the ecosystem, and a large zone of detrimental hypoxia forms consistently during summer months off Louisiana. The size of the hypoxic zone is directly proportional to river flow volume and the delivery of nitrate. The broad continental slope south of Texas and Louisiana is riddled with numerous basins that are tens of kilometers in diameter and hundreds of meters deep relative to the surrounding slope, but the habitats in each can vary from lakes of oil and salt surrounded by dense populations of mussels to simple depauperate mud-lined basins. Offshore of the continental shelf, the productivity and species composition of the plankton of the Gulf of Mexico ecosystem are controlled by the source water (Caribbean) and concomitant physical processes.

Total mercury (THg) and methylmercury (MeHg) were recorded in the commercial demersal fish Lethrinus nebulosus, caught from six locations in Qatar EEZ (Exclusive Economic Zone). Concentrations of THg decreased in the order: liver˃muscle˃gonad. THg concentrations in fish tissue ranged from 0.016ppm in gonad to 0.855ppm (mgkg-1w/w) in liver tissues, while concentrations in muscle tissue ranged from 0.24 to 0.49ppm (mgkg-1w/w) among sampling sites. MeHg concentrations were used to validate food web transfer rate calculations. Intake rates were calculated to assess the potential health impact of the fish consumption. There is no major threat to human health from the presence of Hg in L. nebulosus, based upon reasonable consumption patterns, limited to no more than three meals of L. nebulosus per week.