peer reviewed | Plastic debris are accumulating in the marine environment and aggregate microorganisms that form a new ecosystem called the plastisphere. Better understanding the plastisphere is crucial as it has self-sufficient orga- nization and carries pathogens or organisms that may be involved in the pollutant adsorption and/or plastic degradation. To date, the plastisphere is mainly described at the taxonomic level and the functioning of its microbial communities still remains poorly documented. In this work, metagenomic and metaproteomic analyzes were performed on the plastisphere of polypropylene and polyethylene plastic debris sampled on a pebble beach from the Mediterranean Sea. Our results confirmed that the plastisphere was organized as self-sufficient eco- systems containing highly active primary producers, heterotrophs and predators such as nematode. Interestingly, the chemical composition of the polymer did not impact the structure of the microbial communities but rather influenced the functions expressed. Despite the fact that the presence of hydrocarbon-degrading bacteria was observed in the metagenomes, polymer degradation metabolisms were not detected at the protein level. Finally, hydrocarbon degrader (i.e., Alcanivorax) and pathogenic bacteria (i.e., Vibrionaceae) were observed in the plas- tispheres but were not very active as no proteins involved in polymer degradation or pathogeny were detected. This work brings new insights into the functioning of the microbial plastisphere developed on plastic marine debris.

Plastic debris are accumulating in the marine environment and aggregate microorganisms that form a new ecosystem called the plastisphere. Better understanding the plastisphere is crucial as it has self-sufficient organization and carries pathogens or organisms that may be involved in the pollutant adsorption and/or plastic degradation. To date, the plastisphere is mainly described at the taxonomic level and the functioning of its microbial communities still remains poorly documented. In this work, metagenomic and metaproteomic analyzes were performed on the plastisphere of polypropylene and polyethylene plastic debris sampled on a pebble beach from the Mediterranean Sea. Our results confirmed that the plastisphere was organized as self-sufficient ecosystems containing highly active primary producers, heterotrophs and predators such as nematode. Interestingly, the chemical composition of the polymer did not impact the structure of the microbial communities but rather influenced the functions expressed. Despite the fact that the presence of hydrocarbon-degrading bacteria was observed in the metagenomes, polymer degradation metabolisms were not detected at the protein level. Finally, hydrocarbon degrader (i.e., Alcanivorax) and pathogenic bacteria (i.e., Vibrionaceae) were observed in the plastispheres but were not very active as no proteins involved in polymer degradation or pathogeny were detected. This work brings new insights into the functioning of the microbial plastisphere developed on plastic marine debris.

Wear and tear on fishing gear is a sparsely investigated source of microplastic pollution in the sea. In Norway, Danish seine ropes and trawls are the fishing gears that contribute most to this pollution. The main reason for this pollution is that the seine ropes are dragged along the seabed over a considerable distance, creating a friction force that results in high ropes wear. This note reports the findings after examining the wear of Danish seine ropes used in Norwegian fisheries. The results show that, in Norway alone, an average of 77 to 97 tons of plastic will be added to the sea annually due to this specific fishing gear. Aggregated to include all fly dragging, anchor seining, and pair seining globally, this number is estimated to be about 311 tons per year. | publishedVersion

Wear and tear on fishing gear is a sparsely investigated source of microplastic pollution in the sea. In Norway, Danish seine ropes and trawls are the fishing gears that contribute most to this pollution. The main reason for this pollution is that the seine ropes are dragged along the seabed over a considerable distance, creating a friction force that results in high ropes wear. This note reports the findings after examining the wear of Danish seine ropes used in Norwegian fisheries. The results show that, in Norway alone, an average of 77 to 97 tons of plastic will be added to the sea annually due to this specific fishing gear. Aggregated to include all fly dragging, anchor seining, and pair seining globally, this number is estimated to be about 311 tons per year.

Wear and tear on fishing gear is a sparsely investigated source of microplastic pollution in the sea. In Norway, Danish seine ropes and trawls are the fishing gears that contribute most to this pollution. The main reason for this pollution is that the seine ropes are dragged along the seabed over a considerable distance, creating a friction force that results in high ropes wear. This note reports the findings after examining the wear of Danish seine ropes used in Norwegian fisheries. The results show that, in Norway alone, an average of 77 to 97 tons of plastic will be added to the sea annually due to this specific fishing gear. Aggregated to include all fly dragging, anchor seining, and pair seining globally, this number is estimated to be about 311 tons per year.

Offshore human activities lead to increasing amounts of underwater noise in coastal and shelf environments, which may affect commercially-important benthic invertebrate groups like the re-stocked Helgoland European lobster (Homarus gammarus) in the German Bight (North Sea). It is crucial to understand the impact tonal low-frequency noises, like maritime transport and offshore energy operations, may have on substrate choice and lobsters' behavior to assess potential benefits or bottlenecks of new hard-substrate artificial offshore environments that become available. In this study, we investigated the full factorial effect of a tonal low-frequency noise and predator presence on young-of-year (YOY) European lobsters' in a diurnal and nocturnal experiment. Rocks and European oyster shells (Ostrea edulis) were offered as substrate to YOY lobsters for 3 h. Video recordings (n = 134) allowed the identification of lobsters' initial substrate choice, diel activity and key behaviors (peeking, shelter construction, exploration and hiding). To ensure independence, YOY lobsters in the intermolt stage were randomly selected and assigned to the experimental tanks and used only once. We provide the first evidence that stressors alone, and in combination, constrain YOY lobsters' initial substrate choice towards rocks. During nighttime, the joint effect of exposure to a constant low-frequency noise and predator presence decreased antipredator behavior (i.e., hiding) and increased exploration behavior. Noise may thus interfere with YOY lobsters' attention and decision-making processes. This outcome pinpoints that added tonal low-frequency noise in the environment have the potential to influence the behavior of early-life stages of European lobsters under predator pressure and highlights the importance of including key benthic invertebrates' community relationships in anthropogenic noise risk assessments. Among others, effects of noise must be taken into consideration in plans involving the multi-use of any offshore area for decapods’ stock enhancement, aquaculture, and temporary no-take zones.

Activated carbon (AC) amendment has been shown to reduce bioavailability of hydrophobic contaminants in the bioactive layer of sediment. Unwanted secondary effects of AC amendment could be particularly undesirable for ecologically important seagrass meadows, but so far, only a few studies have been conducted on effects on submerged plants. The purpose of this study was to investigate effects on growth and cover of submerged macrophytes in situ after AC amendment. Test sites were established within a seagrass meadow in the severely contaminated Norwegian fjord Gunneklevfjorden. Here we show that AC amendment does not influence neither cover nor length of plants. Our study might indicate a positive effect on growth from AC in powdered form. Hence, our findings are in support of AC amendment as a low-impact sediment remediation technique within seagrass meadows. However, we recommend further studies in situ on the effects of AC on submerged vegetation and biota. Factors influencing seasonal and annual variation in plant species composition, growth and cover should be taken into consideration. | An In Situ Experimental Study of Effects on Submerged Vegetation After Activated Carbon Amendment of Legacy Contaminated Sediments | acceptedVersion

Embargo until 30 July 2019 | Activated carbon (AC) amendment has been shown to reduce bioavailability of hydrophobic contaminants in the bioactive layer of sediment. Unwanted secondary effects of AC amendment could be particularly undesirable for ecologically important seagrass meadows, but so far, only a few studies have been conducted on effects on submerged plants. The purpose of this study was to investigate effects on growth and cover of submerged macrophytes in situ after AC amendment. Test sites were established within a seagrass meadow in the severely contaminated Norwegian fjord Gunneklevfjorden. Here we show that AC amendment does not influence neither cover nor length of plants. Our study might indicate a positive effect on growth from AC in powdered form. Hence, our findings are in support of AC amendment as a low-impact sediment remediation technique within seagrass meadows. However, we recommend further studies in situ on the effects of AC on submerged vegetation and biota. Factors influencing seasonal and annual variation in plant species composition, growth and cover should be taken into consideration. | acceptedVersion

Activated carbon (AC) amendment has been shown to reduce bioavailability of hydrophobic contaminants in the bioactive layer of sediment. Unwanted secondary effects of AC amendment could be particularly undesirable for ecologically important seagrass meadows, but so far, only a few studies have been conducted on effects on submerged plants. The purpose of this study was to investigate effects on growth and cover of submerged macrophytes in situ after AC amendment. Test sites were established within a seagrass meadow in the severely contaminated Norwegian fjord Gunneklevfjorden. Here we show that AC amendment does not influence neither cover nor length of plants. Our study might indicate a positive effect on growth from AC in powdered form. Hence, our findings are in support of AC amendment as a low-impact sediment remediation technique within seagrass meadows. However, we recommend further studies in situ on the effects of AC on submerged vegetation and biota. Factors influencing seasonal and annual variation in plant species composition, growth and cover should be taken into consideration. Graphical Abstract The effects of activated carbon amendment to growth and cover of submerged macrophytes were tested in an in situ experiment

Embargo until 22 July 2019 | Effects of water-based drill cuttings on sediment reworking activity were studied on two important benthic bioturbators (the bivalve Abra segmentum and the brittle star Amphiura filiformis) using thin aquaria, fluorescentdyed sediment particles (luminophores), time lapse photography and image analysis. In the present context, sediment reworking activity was measured as maximum mixing depth and total amount of luminophores transported below the sediment-water interface. There was a significant reduction in the amount of downward transported luminophores in drill cuttings treatments compared to controls with added natural sediments for both species, which also was true regarding maximum mixing depth for A. segmentum. Further, A. filiformis showed a clearly delayed burrowing of luminophores in the drill cuttings treatment compared to control. To conclude, the study showed that water-based drill cuttings have the potential to reduce sediment reworking. Further, it is evidenced that water-based drill cuttings not only cause burial effects. | acceptedVersion

Effects of water-based drill cuttings on sediment reworking activity were studied on two important benthic bioturbators (the bivalve Abra segmentum and the brittle star Amphiura filiformis) using thin aquaria, fluorescent-dyed sediment particles (luminophores), time lapse photography and image analysis. In the present context, sediment reworking activity was measured as maximum mixing depth and total amount of luminophores transported below the sediment-water interface. There was a significant reduction in the amount of downward transported luminophores in drill cuttings treatments compared to controls with added natural sediments for both species, which also was true regarding maximum mixing depth for A. segmentum. Further, A. filiformis showed a clearly delayed burrowing of luminophores in the drill cuttings treatment compared to control. To conclude, the study showed that water-based drill cuttings have the potential to reduce sediment reworking. Further, it is evidenced that water-based drill cuttings not only cause burial effects.