Seafood is the main source of methylmercury (MeHg) exposure for humans and elevated total mercury (Hg) concentrations have been reported in marine fish from Norwegian fjords compared with offshore areas. Hg in tusk fillets (n = 201) and liver samples (n = 177) were measured in individuals from different habitats including offshore, coastal area, outer and inner Sognefjord. Specifically, the effects of habitat, energy sources and trophic complexity on Hg bioaccumulation pathways in tusk (Brosme brosme) were investigated using stable isotopes of carbon (δ13C) and nitrogen (δ15N). The concentrations of Hg in tusk increased from offshore towards inner Sognefjord. While Hg concentrations in sediment were at background levels, tusk fillet samples from 7 of 8 sites in Sognefjord had higher Hg levels than the maximum level set by European Union. Based on these findings, human consumption advice for tusk from Sognefjord was issued by the Norwegian Food Safety Authority. δ13C values in tusk successfully discriminated individuals from different habitats and were positively correlated to Hg concentrations in tusk across individuals, sites and habitats, outlining the potential importance of terrestrial carbon and most likely the atmospheric deposition of Hg from the catchment to the overall Hg bioaccumulation and exposure regime in tusk. Additionally, we postulate that the effects of terrestrial carbon sources increased towards inner Sognefjord and likely influenced Hg bioavailability throughout the food web. In contrast, δ15N values were patchy throughout the fjord system and although trophic position explained some of the Hg variation between individual fish, it was not correlated with Hg variation across sites and habitats. Our results suggest that tusk can accumulate high levels of Hg in fjord ecosystems and that catchment runoff is likely an important driver of Hg bioaccumulation in this species. | publishedVersion

An accurate representation of the particle organic matter (POM) footprint is necessary in order to effectively predict impacts upon benthic communities and the risk of excessive organic enrichment beneath aquaculture sea-cages. Consequently, bottom-related processes such as particle resuspension must be adequately parametrized and evaluated in the available numerical models. We implemented two approaches to model POM resuspension in a Lagrangian particle tracking model and compared their influence on footprint extension and gradients of depositional flux against a no-resuspension scenario. We performed simulations in both exposed and protected aquaculture locations, and at different stages of the Atlantic Salmon (Salmo salar) production cycle in Norway. Our results indicate that the use of sediment-dependent thresholds for resuspension has the potential to regulate the high levels of erosion produced when selecting a low critical value in constant-threshold approaches, particularly in dynamic environments with mixed sediment types. | publishedVersion

peer reviewed | Protected

Chlordecone, applied on soils until 1993 to control banana weevil, has polluted water resources in the French West Indies for more than 40 years. At the watershed scale, chlordecone applications were not homogenous, generating a spatial heterogeneity of the pollution. The roles of climate, hydrology, soil, agronomy, and geology on watershed functioning generate a temporal heterogeneity of the pollution. This study questions the interactions between practices and the environment that induce such variability. We analyzed hydrological and water pollution datasets from a 2-year monitoring program on the Galion watershed in Martinique (French West Indies). We conjointly analyzed (i) weekly chlordecone (CLD) concentration monitored on 3 river sampling sites, (ii) aquifer piezometric dynamics and pollutions, and (iii) agricultural practices on polluted soils. Our results showed that chlordecone pollution in surface waters are characterized by annual trends and infra-annual variations. Aquifers showed CLD concentration 10 times higher than surface water, with CLD concentration peaks during recharge events. We showed strong interactions between rainfall events and practices on CLD pollution requiring a systemic management approach, in particular during post-cyclonic periods. Small sub-watershed with high CLD pollution appeared to be a substantial contributor to CLD mass transfers to the marine environment via rivers and should therefore receive priority management. We suggest increasing stable organic matter return to soil as well as external input of organic matter to reduce CLD transfers to water. We identified hydrological conditions—notably drying periods—and tillage as the most influential factors on CLD leaching. In particular, tillage acts on 3 processes that increases CLD leaching: organic matter degradation, modification of water paths in soil, and allophane clay degradation.

The In Situ Chemical Reduction (ISCR) process was tested in a nitisol in a French Caribbean banana plantation using five different soil amendments. The addition of 2.8% or 4.0% of Zero Valent Iron (ZVI; dw/dw, 2 different trial plots) in the 0–40-cm soil layer lowered the initial chlordecone (CLD) concentration by up to 74% or 69% in 37 days or 94 days, with 75% of the decrease achieved after only 21 or 24 days of treatment depending on the trial plot. The addition of commercially available Daramend® was also tested by applying the 6% dose (dw/dw) recommended by the manufacturer and using either the regular alfalfa-based product or a bagasse-based product specifically formulated for the study. Both significantly lowered CLD concentrations, but to a lesser extent than with the ZVI-only amendment. A bagasse-ZVI mixture prepared on site produced results slightly better than the two Daramend®. The percentage decreases in CLD concentrations were correlated with the negative redox potentials achieved. In all the trial plots, dechlorinated transformation products appeared in the soil and soil water as the CLD concentrations decreased, with H atoms replacing up to 4 and 7 of the 10 Cl atoms, respectively. None of these degradation products appeared to accumulate in the soil or soil water during the treatment. Instead, the reverse occurred, with an overall downward trend in their concentrations over time. The effects of ISCR treatment on agronomic and human health–related parameters were measured in three different crops. The radishes produced with some treatments were visually of lower quality or smaller in size than those grown in the control plots. Lower yields were observed for the cucumbers and sweet potatoes grown after applying the bagasse-based amendments. Mortality among cucumber seedlings was observed after treatment with ZVI only. Simple operational solutions should suffice to remedy these negative agronomic effects. As regards human health–related effects, the CLD concentrations in radishes grown with three of the amendments were significantly lower than in the two control plots and well below the maximum residue level (MRL), which was substantially exceeded in the radishes grown on untreated soil. For cucumbers, the treatments with regular Daramend® and with a local bagasse-ZVI mixture produced fruits with CLD below the MRL and also below the concentrations in one of the two control plots. As for the sweet potatoes, adding a bagasse-ZVI mixture had a significant positive effect by decreasing contamination below the levels in the two control plots and below the MRL.

Increased knowledge about the fate and behaviour of weathered oil in different sea ice conditions is essential for our ability to model oil spill trajectories in ice more precisely and for oil spill response decision making in northern and Arctic areas. As part of the 3-year project: “Fate, Behaviour and Response to Oil Drifting into Scattered Ice and Ice Edge in the Marginal Ice Zone”, a novel wave and current flume was built to simulate these processes in the laboratory. This paper discusses some of the findings from this project, which included Marine Gas Oil and four Norwegian crude oils. All crude oils were weathered prior to testing, simulating having drifted on the sea surface for a period (tentatively 1–3 days) before encountering ice. The build-up of oil drifting against an ice barrier and horizontal and vertical migration of oil droplets under solid ice and in frazil ice was studied. | publishedVersion

Oil slick thickness is a key parameter for the behaviour of oil spilled at sea. It influences evaporation and entrainment, viable response options, and the risk to marine life at the surface. Determining this value is therefore of high relevance in oil spill modelling. In open water, oil can spread as thin films due to gravity alone, and may be further dispersed by horizontal diffusion and differential advection. In the presence of ice, however, a thin oil slick may become concentrated to higher thickness, if compressed against the ice edge. In the present study, we develop a simple model for the thickness of oil forced against a barrier by a current. We compare our theory to flume experiments, and obtain reasonable agreement. We describe an implementation in a Lagrangian oil spill model, and present some examples. We discuss the operational applicability, and suggest further research needs. | publishedVersion

In this study, the formation and fate of oil-related aggregates (ORAs) from chemically dispersed oil in seawater (SW) were investigated at different temperatures (5 °C, 13 °C, 20 °C). Experiments in natural SW alone, and in SW amended with typical marine snow constituents (phytoplankton and mineral particles), showed that the presence of algae stimulated the formation of large ORAs, while high SW temperature resulted in faster aggregate formation. The ORAs formed at 5 °C and 13 °C required mineral particles for sinking, while the aggregates also sank in the absence of mineral particles at 20°. Early in the experimental periods, oil compound accumulation in ORAs was faster than biodegradation, particularly in aggregates with algae, followed by rapid biodegradation. High abundances of bacteria associated with hydrocarbon biodegradation were determined in the ORAs, together with algae-associated bacteria, while clustering analyses showed separation between bacterial communities in experiments with oil alone and oil with algae/mineral particles. | publishedVersion

Embargo until 01 March 2022 | Microplastics were sampled in open surface waters by using a manta trawl and an in-situ filtering pump. A total of 24 trawl samples and 11 pump samples were taken at 12 locations around Sweden. Overall, the concentration of microplastic particles was higher in pump samples compared to trawl samples. The median microplastic particle concentration was 0.04 particles per m−3 for manta trawl samples and 0.10 particles per m−3 in pump samples taken with a mesh size of 0.3 mm. The highest concentrations were recorded on the west coast of Sweden. Fibers were found in all samples and were also more frequent in the pump samples. Even higher concentrations of fibers and particles were found on the 0.05 mm pump filters. Using near-infrared hyperspectral imaging the majority of the particles were identified as polyethylene followed by polypropylene. | acceptedVersion

Anti-sea lice pesticides, used in the salmonid aquaculture industry, are a growing environmental concern due to their potential to adversely affect non-target crustaceans. Azamethiphos and deltamethrin are two bath treatment pesticides used on salmon farms in Norway, however, limited information is available on their impact on European lobster (Homarus gammarus) larvae in the Norwegian marine environment. Here, we firstly report the lethal (LC50) and effective (EC50) concentrations of azamethiphos and deltamethrin for stage I and stage II larvae, following 1-h exposures. Using a hydrodynamic model, we also modelled the dispersal of both compounds into the marine environment around selected Norwegian farms and mapped the potential impact zones (areas that experience LC50 and EC50 concentrations) around each farm. Our data shows that azamethiphos and deltamethrin are acutely toxic to both larval stages, with LC50 and EC50 values below the recommended treatment concentrations. We also show that the azamethiphos impact zones around farms were relatively small (mean area of 0.04–0.2 km2), however deltamethrin impact zones covered much larger areas (mean area of 21.1–39.0 km2). These findings suggest that deltamethrin poses a significant risk to European lobster in the Norwegian marine environment while the impact of azamethiphos may be less severe. | publishedVersion