Variability of present and past PAH concentrations in sediments of the SW Barents Sea

Published version. Source at http://www.geologi.no/index.php/norwegian-journal-of-geology-91/details/1/538-538.The concentration and distribution of polyaromatic hydrocarbons (PAHs) in surface and subsurface sediment samples from Tromsøflaket and Ingøydjupet, southwestern Barents Sea, were investigated in order to provide insight into the levels and origins of PAHs in a region with petroleum activities. PAH profiles in sediments were evaluated in context with sediment grain size and total organic carbon in order to assess the influence of ocean currents on the transportation and deposition of PAHs. The PAH concentrations are of background (Level I) to good level (Level II) based on the Water Framework Directive classification system. SUM PAH (SUM of 26 PAH compounds) ranged from 39 to 2197 µg/kg (average 225 µg/kg), and NPD (naphthalene, phenanthrene and dibenzothiophene, including their C1–C3 alkyl homologues) in surface samples ranged from 14 to 2045 µg/kg (average 157 µg/kg). However, the average values presented here are higher than have been reported in previous studies. The observed changes in PAH contents in surface and subsurface sediments vary in accordance with changes in grain size (clay and silt 17–99%) and total organic carbon content (0.37–0.98%). In turn, these sedimentary parameters are controlled by the inflow of Atlantic Water and the strength of the two predominating current systems in this region: the North Atlantic Current and Norwegian Coastal Current. Source-allocation modeling suggests that PAHs in surface samples are mainly of pyrogenic or mixed pyrogenic and petrogenic origin. Taken together, these patterns of PAH levels and sources reflect natural variability, indicating that the derived dataset establishes a pre-impacted baseline of the present state of the seafloor

Spatio-temporal patterns of PAHs, PCBs and HCB in sediments of the western Barents Sea

Source at https://doi.org/10.5697/oc.53-4.1005.We examine the composition and levels of organic contaminants (PAHs, PCB, HCB) in four sediment cores collected from the Barents Sea. We assess the influence of temporal variations in contaminant supplies and post-depositional reworking on contaminant distribution. Anthropogenic levels of ∑ 12PAH reached 95 ng g−1, higher inventories dominated by BKF were observed at southern stations, while northern stations exhibited lower inventories with PHE as the dominant compound. The PCB composition was similar at all stations dominated by CB 101, 138 and 153. ∑7PCB concentrations were higher at northern stations. The observed composition and spatio-temporal pattern of organic contaminants is in accordance with long-range transport supplies

Natural variability of benthic foraminiferal assemblages and metal concentrations during the last 150 years in the Ingøydjupet trough, SW Barents Sea.

Submitted manuscript version. Published version available at http://dx.doi.org/10.1016/j.marmicro.2015.09.005While today the SW Barents Sea is a relatively un-impacted and uncontaminated area, industrial activities related to the petroleum industry are projected to increase in the coming decades. This makes the area a valuable natural laboratory to establish pre-impacted baselines as a precursor for future seabed monitoring programs. Here we present benthic foraminiferal assemblages and metal concentrations in four sediment cores from the Ingøydjupet trough, SW Barents Sea, covering approximately the last 150 years. This information supports the application of foraminiferal assemblages as a bio-monitoring tool applicable in high latitudes. At all stations, metal concentrations in the sediment correspond to no effect concentrations. The downcore metal concentrations are mainly attributed to natural variability of the clay fraction and total organic content of the sediments. Agglutinated foraminifera are poorly preserved down-core. Patterns in the calcareous foraminiferal assemblages suggest an enhanced food supply as a result of increased Atlantic Water inflow through the region during the last 150 years. At near-shore stations, the Norwegian Coastal Current additionally influences assemblages. Decadal scale climatic oscillations are indicated by increased calcareous fluxes and are attributed to variability in the food-rich Atlantic Water. This study serves as an important baseline data set prior to increasing industrial activities in the SW Barents Sea, and thereby contributes to a better understanding of natural environmental variability

The Postglacial response of Arctic Ocean gas hydrates to climatic amelioration

Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate change, the processes and rates of subsurface/atmospheric natural gas exchange remain uncertain. Here we investigate the dynamics between gas hydrate stability and environmental changes from the height of the last glaciation through to the present day. Using geophysical observations from offshore Svalbard to constrain a coupled ice sheet/gas hydrate model, we identify distinct phases of subglacial methane sequestration and subsequent release on ice sheet retreat that led to the formation of a suite of seafloor domes. Reconstructing the evolution of this dome field, we find that incursions of warm Atlantic bottom water forced rapid gas hydrate dissociation and enhanced methane emissions during the penultimate Heinrich event, the B?lling and Aller?d interstadials, and the Holocene optimum. Our results highlight the complex interplay between the cryosphere, geosphere, and atmosphere over the last 30,000 y that led to extensive changes in subseafloor carbon storage that forced distinct episodes of methane release due to natural climate variability well before recent anthropogenic warmingauthorsversionPeer reviewe

Prospecting biotechnologically-relevant monooxygenases from cold sediment metagenomes: An in silico approach

Source at https://doi.org/10.3390/md15040114.The goal of this work was to identify sequences encoding monooxygenase biocatalysts with novel features by in silico mining an assembled metagenomic dataset of polar and subpolar marine sediments. The targeted enzyme sequences were Baeyer–Villiger and bacterial cytochrome P450 monooxygenases (CYP153). These enzymes have wide-ranging applications, from the synthesis of steroids, antibiotics, mycotoxins and pheromones to the synthesis of monomers for polymerization and anticancer precursors, due to their extraordinary enantio-, regio-, and chemo- selectivity that are valuable features for organic synthesis. Phylogenetic analyses were used to select the most divergent sequences affiliated to these enzyme families among the 264 putative monooxygenases recovered from the ~14 million protein-coding sequences in the assembled metagenome dataset. Three-dimensional structure modeling and docking analysis suggested features useful in biotechnological applications in five metagenomic sequences, such as wide substrate range, novel substrate specificity or regioselectivity. Further analysis revealed structural features associated with psychrophilic enzymes, such as broader substrate accessibility, larger catalytic pockets or low domain interactions, suggesting that they could be applied in biooxidations at room or low temperatures, saving costs inherent to energy consumption. This work allowed the identification of putative enzyme candidates with promising features from metagenomes, providing a suitable starting point for further developments

A standard protocol for describing the evaluation of ecological models

Numerical models of ecological systems are increasingly used to address complex environmental and resource management questions. One challenge for scientists, managers, and stakeholders is to appraise how well suited these models are to answer questions of scientific or societal relevance, that is, to perform, communicate, or access transparent evaluations of ecological models. While there have been substantial developments to support standardised descriptions of ecological models, less has been done to standardise and to report model evaluation practices. We present here a general protocol designed to guide the reporting of model evaluation. The protocol is organised in three major parts: the objective(s) of the modelling application, the ecological patterns of relevance and the evaluation methodology proper, and is termed the OPE (objectives, patterns, evaluation) protocol. We present the 25 questions of the OPE protocol which address the many aspects of the evaluation process and then apply them to six case studies based on a diversity of ecological models. In addition to standardising and increasing the transparency of the model evaluation process, we find that going through the OPE protocol helps modellers to think more deeply about the evaluation of their models. From this last point, we suggest that it would be highly beneficial for modellers to consider the OPE early in the modelling process, in addition to using it as a reporting tool and as a reviewing tool.publishedVersio

A communal catalogue reveals Earth's multiscale microbial diversity

Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.Peer reviewe

Experimental studies of reproduction and feeding for two Arctic-dwelling Calanus species exposed to crude oil

Copepods of the genus Calanus are keystone species in the transfer of energy from lower to higher trophic levels of the Arctic/sub-Arctic food web. We performed experimental tests on the reproduction and feeding of Calanus spp. exposed to the water-soluble fraction (WSF) of crude oil. Fecal pellet and egg production were examined for females of C. glacialis exposed to WSF (16 EPA) concentrations of 10.4 μg l–1 (high treatment; HT), 3.6 μg l–1 (low treatment; LT) and 0 μg l–1 (control treatment; CT). We observed no significant difference in cumulative egg or fecal pellet production. Egg hatching success was examined for 2 d after transferring eggs from treatment solutions to uncontaminated seawater. Hatching success was significantly lower in the HT compared to the CT. In a second experiment, feeding of C. finmarchicus was examined after exposure for 11 and 18 d to 7.0 (HT), 3.4 (LT) or 0 (CT) μg l–1 of WSF (16-EPA). Using algae cell concentrations as a proxy for feeding success, feeding was inhibited for C. finmarchicus specimens exposed to the HT of WSF compared to the CT. Our findings indicate that adult females of C. glacialis may withstand some exposure to crude oil components but the survival of offspring is negatively affected. Reduced feeding efficiency in C. finmarchicus exposed to high concentrations of WSF provides evidence that adult specimens are sensitive to exposure to crude oil. The study expands on the limited body of knowledge of potential changes to key life history traits of Arctic Calanus species resulting from exposure to chemical compounds in crude oil

Cold seeps in a warming Arctic : Insights for benthic ecology

Cold-seep benthic communities in the Arctic exist at the nexus of two extreme environments; one reflecting the harsh physical extremes of the Arctic environment and another reflecting the chemical extremes and strong environmental gradients associated with seafloor seepage of methane and toxic sulfide-enriched sediments. Recent ecological investigations of cold seeps at numerous locations on the margins of the Arctic Ocean basin reveal that seabed seepage of reduced gas and fluids strongly influence benthic communities and associated marine ecosystems. These Arctic seep communities are mostly different from both conventional Arctic benthic communities as well as cold-seep systems elsewhere in the world. They are characterized by a lack of large specialized chemo-obligate polychetes and mollusks often seen at non-Arctic seeps, but, nonetheless, have substantially higher benthic abundance and biomass compared to adjacent Arctic areas lacking seeps. Arctic seep communities are dominated by expansive tufts or meadows of siboglinid polychetes, which can reach densities up to >3 × 105 ind.m–2. The enhanced autochthonous chemosynthetic production, combined with reef-like structures from methane-derived authigenic carbonates, provides a rich and complex local habitat that results in aggregations of non-seep specialized fauna from multiple trophic levels, including several commercial species. Cold seeps are far more widespread in the Arctic than thought even a few years ago. They exhibit in situ benthic chemosynthetic production cycles that operate on different spatial and temporal cycles than the sunlight-driven counterpart of photosynthetic production in the ocean’s surface. These systems can act as a spatio-temporal bridge for benthic communities and associated ecosystems that may otherwise suffer from a lack of consistency in food quality from the surface ocean during seasons of low production. As climate change impacts accelerate in Arctic marginal seas, photosynthetic primary production cycles are being modified, including in terms of changes in the timing, magnitude, and quality of photosynthetic carbon, whose delivery to the seabed fuels benthic communities. Furthermore, an increased northward expansion of species is expected as a consequence of warming seas. This may have implications for dispersal and evolution of both chemosymbiotic species as well as for background taxa in the entire realm of the Arctic Ocean basin and fringing seas