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MARINFORSK-Marine ressurser og miljø

Fluxes and Fate of Microplastics in Northern European Waters

Alternative title: Spredning og endepunkter for mikroplast i nordeuropeiske farvann

Awarded: NOK 0.90 mill.

Fluxes and Fate of Microplastics in Northern European Waters (FACTS) was started with the intention to create new knowledge and improve our understanding of the origin of microplastic in the northern European oceans, along which routes it is transported, and where it ends up. Investigated transport processes include the patterns in which the microplastic moves in the water, transport through the air, the development of clumps of microplastic with oceanic life forms and their remnants, and how this influences the sinking of microplastic. This was studied on a large scale in the open ocean and on a smaller scale in the better-known fjord system around Bergen. FACTS included sampling campaigns between Germany and Svalbard, where samples were collected from research vessels, fishery vessels, and smaller boats. The first cruise took place on 5. June to 8. of Juli 2021 from Bremerhaven to the west of Bear Island, water and marine snow samples were collected. In 2022 IMR participated in the Bergen fjord sampling campaign from May 30th to June 5th where 10 stations were sampled for microplastic analyses. Stations were selected based on oceanographic modeling and covered coastal current (Øygarden), the Bergen fjord system, and Veafjorden at Osterøy. Material sampled were surface water (with different filter sizes from 1 µm, 10 µm, and 300 µm) at different depths in the water column (filter size 10 µm), sediment. In total 285 fishes (cod and tusk) were caught. Fishes were caught from ten stations from South of Svalbard, West of Tromsøyflaket, Lofoten, Vestfjorden, Stadhavet, West of Shetland, South for Fedje, Byfjorden at the Askøy bridge, at Lindesnes and at Gøteborg by the reference fleet (commercial fishermen collaborating with the Institute of Marine Research (IMR), IMR research cruises and the Swedish IBTS cruise, one private fisher and on the FACTS project cruise in the Byfjorden. Fish was analyzed for mikroplastic >10 µm at the IMR microplastic laboratory. Fish from selected stations were analysed for additives, microplastic >1 µm and tyre abrasion particles. For water and sediments, it was measured in which depths the microplastic mainly occurs, where the Skagerrak was predicted to be the major occurrence zone. Analyses are ongoing and will be reported during 2024. Measured microplastic particle concentrations will be compared with computed microplastic particle distribution models based on ocean currents, and the models will be adjusted based on the findings. The model will calculate the contamination and transport of microplastic over time. The work done in 2022 was in support of the work package leader (WP1) in Germany (Gunnar Gerdts et al., AWI) with particle tracking analyses. Here we used IMR's particle tracking algorithm LADIM as well as the large-scale ocean model archive SVIM (4 km resolution over the Norwegian/North/Barents Seas) to simulate the dispersion of plastic particles from localities that were sampled during the cruise June-July 2021. The simulations were run for 20 days forward in time (to reveal potential further spread northwards) and 20 days backward in time (to reveal where the particles may come from). Preliminary results indicate a large-scale northward transport from all transects, in line with the current understanding of the Norwegian Atlantic Current and the Norwegian Coastal Current. The plan going forward is to support the collaborators at AWI toward a publication that links observed microplastic concentrations along the Norwegian coast with ocean model results. Finally, IMR will support the project leader of FACTS (Jes Vollertsen, Danmark) to summarize gained knowledge on microplastic and convey the gained knowledge to European decision-makers and the international public.

Large scale modelling and sampling: supporting our main collaborators at AWI we have gained an overview of microplastic concentrations in Norwegian main water masses. IMR was instrumental to designing the overall sampling strategy and to model the northwards trajectories of the sampled water masses using our established ocean model archives and particle trajectory software. Impacts include increased understanding of flow of microplastic from northern Europe to the Arctic. Better understanding of sources, transport and fate of microplastics in the fjord Byfjorden in the Bergen area are gained based on oceanographic models and knowledge on sources like run off from roads and bridges and discharges from sewage treatments plants. Fish samples analyses detected and measured microplastic >10 µm in fillet and liver from 10 different stations in two species with µFTIR. Amounts larger than in controls were found, showing that microplastic can be taken up into fillet and liver. Levels were generally low, usually in the order of 1 particle/g. Data on occurrence in fillet and liver is hard to compare due to methodological differences, but work from others with similar methods also resulted in detection of amounts in the same order of magnitude. There are limitations to the methods used. Some polymer types are more prone to loss than others. Measurement uncertainties for microplastic particles below 50 µm are not well established yet. Therefore, it is possible that the numbers in that size category are underestimated, generally in all studies, including ours. Some stations were also analyzed for tyre wear, for smaller microplastic >1 µm and additives. The numbers of smaller microplastics were much higher than those for larger ones, however more robust data is needed to conclude this with high certainty. Additive analysis showed a rough trend similar to what was found in numbers of plastic particles, but also here, the data is too scarce for robust conclusions. This data emphasizes the necessity to continue improving methods to enable a risk assessment. The increasing evidence of presence of microplastic particles not only in sediment and water, and in the intestinal tract of animals, but also in tissues, combined with effect studies showing adverse effects and synergy with additives and other contaminants such as pesticides (Varshney et al. 2023) which increase adverse effects, clearly advocates for investigations and management. Analysis of the data in context to the data of the project partners in water and sediment might show some trends connecting microplastics and additives occurrence in ocean currents and sources. Results will be published in peer-reviewed journals.

FACTS will create new knowledge and improve our mechanistic understanding of the sources, transport, occurrence, and fate of small microplastics in the northern marine waters. FACTS will combine state-of-the-art analytical, monitoring and modelling approaches in feedback cycles to describe the transport and geographical sources of microplastics contamination as well as sinks from the temperate waters of the southern North Sea to the Arctic waters of the Barents Sea. It analyses the distribution of MP in the water column and quantifies Skagerrak as a major sink zone. Investigated transport processes range from drift scenarios to air transport to aggregation and sinking processes. FACTS also zooms in on the geographic scale to study microplastic transport and fate in a semi-enclosed fjord system. The goal is to address the question of how MP move vertically in the water column with time under comparatively well-defined hydrodynamic conditions. FACTS is structured around a set of sampling campaigns reaching from the German Bight to Svalbard, where samples are collected from large research vessels, smaller research vessels, fishery vessels and land-based boats. Plastic particle concentrations, obtained from the proposed sampling campaigns are implemented into oceanographic models. The modelling approach is used to integrate release and transport scenarios, and the likelihood and timescale for particle pathways are estimated based on sinking, defragmentation, and beaching rates, obtained from observations. FACTS will be enhanced by tackling the current challenges of nanoplastics and tyre wear particle detection in marine samples. Both particle types are currently not accessible for mass balances of marine plastics contamination. Finally, FACTS synthesises the knowledge gained and disseminates it to a wide range of stakeholders, ranging from other scientists to European decision-makers.

Funding scheme:

MARINFORSK-Marine ressurser og miljø