418 research outputs found
Temporal changes in deep-sea sponge populations are correlated to changes in surface climate and food supply
No full textDensity and average size of two species of abyssal sponges were analyzed at Station M (?4100 m depth) over an 18-year time-series (1989–2006) using camera sled transects. Both sponge taxa share a similar plate-like morphology despite being within different families, and both showed similar variations in density and average body size over time, suggesting that the same factors may control the demographics of both species. Peaks in significant cross correlations between increases in particulate organic carbon flux and corresponding increases in sponge density occurred with a time lag of 13 months. Sponge density also fluctuated with changes in two climate indices: the NOI with a time lag of 18 months and NPGO with a time lag of 15 months. The results support previous suggestions that increased particulate organic carbon flux may induce recruitment or regeneration in deep-sea sponges. It is unknown whether the appearance of young individuals results from recruitment, regeneration, or both, but the population responses to seasonal and inter-annual changes in food supply demonstrate that sponge populations are dynamic and are capable of responding to inter-annual changes despite being sessile and presumably slow-growing
Connections between climate, food limitation, and carbon cycling in abyssal sediment communities
No full textDiverse faunal groups inhabit deep-sea sediments over much of Earth's surface, but our understanding of how interannual-scale climate variation alters sediment community components and biogeochemical processes remains limited. The vast majority of deep-sea communities depend on a particulate organic carbon food supply that sinks from photosynthetically active surface waters. Variations in food supply depend, in part, on surface climate conditions. Proposed ocean iron fertilization efforts are also intended to alter surface production and carbon export from surface waters. Understanding the ecology of the abyssal sediment community and constituent metazoan macrofauna is important because they influence carbon and nutrient cycle processes at the seafloor through remineralization, bioturbation, and burial of the sunken material. Results from a 10-year study in the abyssal NE Pacific found that climate-driven variations in food availability were linked to total metazoan macrofauna abundance, phyla composition, rank-abundance distributions, and remineralization over seasonal and interannual scales. The long-term analysis suggests that broad biogeographic patterns in deep-sea macrofauna community structure can change over contemporary timescales with changes in surface ocean conditions and provides significant evidence that sediment community parameters can be estimated from atmospheric and upper-ocean conditions. These apparent links between climate, the upper ocean, and deep-sea biogeochemistry need to be considered in determining the long-term carbon storage capacity of the ocean
Inter-annual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m)
No full textUnderstanding the dynamics of abyssal community structure and function has become increasingly important as deep-sea resource exploitation and climate change pressures are expected to ramp up. This time-series study investigates macrofaunal polychaete dynamics at a station in the North East Pacific (Sta. M; 35? N 123? W, 4000 m, 1991-2011). Infaunal polychaete species were identified and their proxy biomass and proxy energy use rate estimated. The assemblage comprised 167 species, having a composition consistent with other abyssal areas globally. Significant changes in univariate and multivariate parameters (rank abundance distribution, Simpson’s diversity index, and species and functional group composition) were detected across 1991-2011. However, no change in biomass or energy use rate was apparent through the time-series. The largest changes in the polychaete assemblage coincided with both an increase in sinking particulate organic carbon flux to the seafloor in 2007, and a 40 km relocation of the sampling location to a site 100 m shallower, preventing a conclusive assessment of which might drive the observed variation. Analyses prior to the change of sampling location showed that the polychaete assemblage composition dynamics were primary driven by food supply variation. Changes in several species were also lagged to changes in POC flux by 4 to 10 months. The polychaete fauna exhibited a significant positive relationship between total density and total energy use rate, suggesting population-level tracking of a common resource (e.g. POC flux food supply). Neither compensatory nor energetic zero-sum dynamics were detected among the polychaete assemblage, but the results suggest that the latter occur in the macrofaunal community as a whole. The results do indicate (a) potential control of species composition, and the density of individual key species, by food supply, when the time-series prior to the sampling location was analysed separately, and (b) generally sensitive detection of environmental change by species-level analysis of the abyssal polychaete assemblage
A new aerosol collector for quasi on-line analysis of particulate organic matter: the Aerosol Collection Module (ACM) and first applications with a GC/MS-FID
No full textIn many environments organic matter significantly contributes to the composition of atmospheric aerosol particles influencing its properties. Detailed chemical characterization of ambient aerosols is critical in order to understand the formation process, composition, and properties of aerosols and facilitates source identification and relative contributions from different types of sources to ambient aerosols in the atmosphere. However, current analytical methods are far from full speciation of organic aerosols and often require sampling times of up to one week. Offline methods are also subjected to artifacts during aerosol collection and storage.
In the present work a new technique for quasi on-line compound specific measurements of organic aerosol particles was developed. The Aerosol Collection Module (ACM) focuses particles into a beam which is directed to a cooled sampling surface. The sampling takes place in a high vacuum environment where the gas phase from the sample volume is removed. After collection is completed volatile and semi-volatile compounds are evaporated from the collection surface through heating and transferred to a detector. For laboratory characterization the ACM was interfaced with a Gas Chromatograph Mass Spectrometer, Flame Ionization Detector system (GC/MS-FID), abbreviated as ACM GC-MS. The particle collection efficiency, gas phase transfer efficiency, and linearity of the ACM GC-MS were determined using laboratory generated octadecane aerosols. The ACM GC-MS is linear over the investigated mass range of 10 to 100 ng and a recovery rate of 100% was found for octadecane particles. The ACM GC-MS was applied to investigate secondary organic aerosol (SOA) formed from β-pinene oxidation. Nopinone, myrtanal, myrtenol, 1-hydroxynopinone, 3-oxonopinone, 3,7-dihydroxynopinone, and bicyclo[3,1,1]hept-3-ene-2-one were found as products in the SOA. The ACM GC-MS results are compared to quartz filter samples taken in parallel to the ACM GC-MS measurements. First measurements of ambient atmospheric aerosols are presented.United States. Environmental Protection Agency (grant number RD-83107701-0)United States. Dept. of Energy (grant number DE-FG02-05ER84269
A review of indicators and identification of gaps: Deep-sea habitats
No full textA range of national and international legislation, obligations and commitments aim to promote and maintain a healthy and biologically diverse marine environment from shallow coastal waters to the deep sea. In addition, a set of Contributory Marine Objectives (CMOs) have been developed to meet the Government’s overall vision for clean, safe, healthy, biologically diverse and productive seas. These objectives require sustained and routine observations of oceanic and coastal ecosystems to achieve their goals. This report evaluates the applicability of existing and suggested (where gaps have been highlighted) environmental indicators that can be used to monitor and assess the state of UK deep-sea habitats. These indicators are reviewed against potential anthropogenic pressures, ecosystem structure and function, as well as statutory obligations and CMOs.The principal anthropogenic pressures that may have an impact on UK deep-sea habitats are identified as demersal fisheries, Oil and gas industry activities, land-based/shipping pollution and climate change. At present, there are no routine UK deep-sea environment monitoring programmes and the only protected area in UK deep water is the Darwin Mounds region. This investigation has identified seventeen potential indicators of impacts that can be mapped to the assessment framework, which will be used to implement an integrated monitoring programme.The review of the anthropogenic pressures with regard to relevant indicators highlighted many gaps in current deep-sea habitat monitoring efforts. Gaps that could currently be covered or addressed by suggested indicators are:• The impact of demersal fishing on UK deep-water habitats. This activity is not routinely monitored and its impact is unknown in the vast majority of UK deep-sea habitats, although it is thought to be the principle threat. (Indicator: photographic transects to measure extent, abundance and diversity of habitats).• No routine monitoring programmes on the sustained impact of oil and gas industry activity on deep-sea habitats are in place, although the industry is required to perform initial environmentalimpact assessments. (Indicator: community change around drill sites).• The extent and impact of litter/debris (shipping, fishing and land-based) is unknown in the deep sea (Indicator: photographic transects, will show extent but not effects). Anthropogenic pressures that cannot be addressed with current operational indicators may be addressed by indicators that are under development. Other gaps in monitoring effort requiremore research to improve knowledge of the habitats and the impacts caused by the pressures. Also, monitoring effort should not focus only on ‘charismatic’ species (e.g. corals and sponges).The critical review of the indicators highlighted significant gaps in their accurate implementation:• The extent, abundance and diversity of specific UK deep-sea habitats are poorly understood, or remain unknown. Surveys still recover many species new to science and there is a paucity ofknowledge of deep-sea ecological processes.• The UK does not currently monitor bioaccumulation of contaminants of any kind in deep-sea organisms.• There is no ecotoxicological information for deep-sea organisms.• Molecular and biochemical indicators are potentially useful in revealing contaminant exposure and the health of species, but such techniques remain under development.The review of the indicators in addressing ecosystem structure and function revealed that while some can be used to address ecosystem structure (e.g., photographic transects to reveal extent of specific habitats, species abundance and diversity), there are presently no indicators available to address the issue of ecosystem function directly. Within the deep sea higher biodiversity appears to support higher rates of ecosystem processes and increased efficiency with which these processes are performed. Anthropogenic effects that negatively affectbiodiversity will therefore have a negative impact on ecosystem function. Indicators that monitor biodiversity may therefore act as proxies for monitoring ecosystem function.A review of the current indicators in place suggests that regional and international statutory obligations and CMOs are not being fully addressed or fulfilled, primarily because there are no routine monitoring programmes in UK deep-sea waters. Photographic transects of the seafloor are potentially the most useful for routine monitoring and assessment of the fragile or vulnerable deep-water habitats found in UK waters and will help to address legal obligations. Such habitats include seamounts, carbonate mounds and reefs (notable for the presence of the deep-water coral, Lophelia pertusa), sponge aggregations, octocoral ‘gardens’ and chemosynthetic habitats (cold seeps and pockmarks). However, for monitoring, management and protection programmes to work successfully, we need to increase our knowledge of the location and ecology of these deep-sea habitats in UK waters
Impact of dissolution on the sedimentary record of the Paleocene–Eocene thermal maximum
No full textThe input of massive amounts of carbon to the atmosphere and ocean at the Paleocene–Eocene Thermal Maximum (PETM; ?55.53 Ma?55.53 Ma) resulted in pervasive carbonate dissolution at the seafloor. At many sites this dissolution also penetrated into the underlying sediment column. The magnitude of dissolution at and below the seafloor, a process known as chemical erosion, and its effect on the stratigraphy of the PETM, are notoriously difficult to constrain. Here, we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the PETM at three deep-sea sites characterized by a range of bottom water dissolution intensity. We show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution. We compare these data with dissolution and other proxy records, electron micrograph observations of samples and lithology. The complete data set indicates that the two sites with slower carbonate accumulation, and less active bioturbation, are characterized by significant chemical erosion. At the third site, higher carbonate accumulation rates, more active bioturbation, and possibly winnowing have limited the impacts of dissolution. However, grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records
An evaluation of deep-sea benthic megafauna length measurements obtained with laser and stereo camera methods
No full textThe 25 year time-series collected at Station M, ~4000 m on the Monterey Deep-sea Fan, has substantially improved understanding of the role of the deep-ocean benthic environment in the global carbon cycle. However, the role of deep-ocean benthic megafauna in carbon bioturbation, remineralization and sequestration is relatively unknown. It is important to gather both accurate and precise measurements of megafaunal community abundance, size distribution and biomass to further define their role in deep-sea carbon cycling and possible sequestration. This study describes initial results from a stereo camera system attached to a remotely operated vehicle and analyzed using the EventMeasure photogrammetric measurement software to estimate the density, length and biomass of 10 species of mobile epibenthic megafauna. Stereo length estimates were compared to those from a single video camera system equipped with sizing lasers and analyzed using the Monterey Bay Aquarium Research Institute’s Video Annotation and Reference System. Both camera systems and software were capable of high measurement accuracy and precision (<±1 mm measurement error and precision). However, the oblique angle of the single video camera caused the spatial scale of the image perspective to change with distance from the camera, resulting in error when measurements were not parallel or vertical to two horizontal-oriented scaling lasers. Analysis showed that the stereo system recorded longer lengths and higher biomass estimates than the single video camera system for the majority of the 10 megafauna species studied. The stereo image analysis process took substantially longer than the video analysis and the value of the EventMeasure software tool would be improved with developments in analysis automation. The stereo system is less influenced by object orientation and height, and is potentially a useful tool to be mounted on an autonomous underwater vehicle and for measuring deep-sea pelagic animals where the use of lasers is not feasible
A Southeast Atlantic deep-ocean observatory: first experiences and results
No full textThe DELOS (Deep-ocean Environmental Long-term Observatory System) project is a long-term research program focused on understanding the impacts of oil and gas extraction on deep-sea ecosystems. We have installed two seafloor observation platforms, populated with ROV-serviced sensor modules, at 1400 m water depth in the Southeast Atlantic off the coast of Angola. The 'impact' Near-Field platform is located 50 m from subsea oil production facilities. The ‘control’ Far-Field platform is 16 km distant from any industry seafloor activity. Each platform includes oceanographic, acoustic, and camera sensor modules. The latter carries two still cameras providing close-up and wide-angle views of the seabed. The Far-Field platform is also equipped with a sediment trap that deploys to 100 m above the seafloor. The instrumented platforms were installed in Feb 2009, and the sensor modules subsequently serviced in Aug 2009, Feb 2010, and Aug 2010. Here, we report on our first experiences of operating the observatories and present some of the first data. The oceanographic data (temperature, salinity, oxygen concentration) and biological observations (demersal fish and benthic invertebrates) suggest that the two study sites have near identical environmental characteristics. We, therefore, believe that these sites are appropriate as control and impact locations for long-term monitoring of potential anthropogenic effects referenced to natural background environmental variation. We suggest that DELOS-type observatories, particularly operated as pairs (or in networks), are a highly effective means of appropriately monitoring deep-water resource exploitation-both hydrocarbon extraction and mineral mining
Electrochemical CO<sub>2</sub>Reduction over Metal-/Nitrogen-Doped Graphene Single-Atom Catalysts Modeled Using the Grand-Canonical Density Functional Theory
No full textRenewably driven, electrochemical conversion of carbon dioxide into value-added products is expected to be a critical tool in global decarbonization. However, theoretical studies based on the computational hydrogen electrode largely ignore the nonlinear effects of the applied potential on the calculated results, leading to inaccurate predictions of catalytic behavior or mechanistic pathways. Here, we use grand canonical density functional theory (GC-DFT) to model electrochemical CO2 reduction (CO2R) over metal- and nitrogen-doped graphene catalysts (MNCs) and explicitly include the effects of the applied potential. We used GC-DFT to compute the CO2 to CO reaction intermediate energies at -0.3, -0.7, and -1.2 VSHE catalyzed by MNCs each doped with 1 of the 10 3d block metals coordinated by four pyridinic nitrogen atoms. Our results predict that Sc-, Ti-, Co-, Cu-, and Zn-N4Cs effectively catalyze CO2R at moderate to large reducing potentials (-0.7 to -1.2 VSHE). ZnN4C is a particularly promising electrocatalyst for CO2R to CO both at low and moderate applied potentials based on our thermodynamic analysis. Our findings also explain the observed pH independence of CO production over FeN4C and predict that the rate-determining step of CO2R over FeN4C is not *CO2- formation but rather *CO desorption. Additionally, the GC-DFT-computed density of states analysis illustrates how the electronic states of MNCs and adsorbates change non-uniformly with applied potential, resulting in a significantly increased *CO2- stability relative to other intermediates and demonstrating that the formation of the adsorbed *CO2- anion is critical to CO2R activation. This work demonstrates how GC-DFT paves the way for physically realistic and accurate theoretical simulations of reacting electrochemical systems. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Materials for Energy Conversion and Storag
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