Anthropogenic microlitter in the Baltic Sea water column

Microlitter (0.5–5 mm) concentrations in water column (depth range from 0 to 217.5 m) of the main Baltic Proper basins are reported. In total, 95 water samples collected in 6 research cruises in 2015–2016 in the Bornholm, Gdansk, and Gotland basins were analysed. Water from 10- and 30-litre Niskin bathometers was filtered through the 174 μm filters, and the filtrate was examined under optical microscope (40 ×). The bulk mean concentration was 0.40 ± 0.58 items per litre, with fibres making 77% of them. Other types of particles are the paint flakes (19%) and fragments (4%); no microbeads or pellets. The highest concentrations are found in the near-bottom samples from the coastal zone (2.2–2.7 items per litre max) and from near-surface waters (0.5 m) in the Bornholm basin (5 samples, 1.6–2.5 items per litre). Distribution of particles over depths, types, and geographical regions is presented.

A. Bagaev, L. Khatmullina, I. Chubarenko, Marine Pollution Bulletin, Available online 26 October 2017, In Press

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No increase in marine microplastic concentration over the last three decades – A case study from the Baltic Sea

Microplastic is considered a potential threat to marine life as it is ingested by a wide variety of species. Most studies on microplastic ingestion are short-term investigations and little is currently known about how this potential threat has developed over the last decades where global plastic production has increased exponentially. Here we present the first long-term study on microplastic in the marine environment, covering three decades from 1987 to 2015, based on a unique sample set originally collected and conserved for food web studies. We investigated the microplastic concentration in plankton samples and in digestive tracts of two economically and ecologically important planktivorous forage fish species, Atlantic herring (Clupea harengus) and European sprat (Sprattus sprattus), in the Baltic Sea, an ecosystem which is under high anthropogenic pressure and has undergone considerable changes over the past decades. Surprisingly, neither the concentration of microplastic in the plankton samples nor in the digestive tracts changed significantly over the investigated time period. Average microplastic concentration in the plankton samples was 0.21 ± 0.15 particles m− 3. Of 814 fish examined, 20% contained plastic particles, of which 95% were characterized as microplastic (< 5 mm) and of these 93% were fibres. There were no significant differences in the plastic content between species, locations, or time of day the fish were caught. However, fish size and microplastic in the digestive tracts were positively correlated, and the fish contained more plastic during summer than during spring, which may be explained by increased food uptake with size and seasonal differences in feeding activity. This study highlights that even though microplastic has been present in the Baltic environment and the digestive tracts of fishes for decades, the levels have not changed in this period. This underscores the need for greater understanding of how plastic is cycled through marine ecosystems. The stability of plastic concentration and contamination over time observed here indicates that the type and level of microplastic pollution may be more closely correlated to specific human activities in a region than to global plastic production and utilization as such.

Sabrina Beer, Anders Garm, Bastian Huwer, Jan Dierking, Torkel Gissel Nielsen, Science of The Total Environment, Available online 19 October 2017, In Press

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Marine litter at the seafloor – Abundance and composition in the North Sea and the Baltic Sea

Litter is present in all marine waters around the globe. It consists of several compound classes of which plastic is of special interest because of its high abundance and possible threat to marine organisms. The regional distribution, composition and abundance of large litter items (LI) at the sea floor of the North Sea and the Baltic Sea were investigated based on 175 bottom trawls between 2013 and 2015. Different types of marine litter > 2.5 cm were classified according to the protocol of the ICES International Bottom Trawl Survey. The results showed considerable geographical variation: In the North Sea, a mean litter abundance of 16.8 LI/km2 was found, whereas the litter abundance in the Baltic Sea was significantly lower (5.07 LI/km2). In general, plastic represented 80% of the litter items. During the study, some methodical aspects with possible impact on the results were identified that need to be addressed in future sampling campaigns.

Ulrike Kammann, Marc-Oliver Aust, Horst Bahl, Thomas Lang, Marine Pollution Bulletin, Available online 12 October 2017, In Press

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Persistent organic pollutants in selected fishes of the Gulf of Finland

Fish samples of Baltic herring, sprat, flounder, perch, salmon, and river lamprey were collected from the Gulf of Finland in 2013 and 2014 with the aim to get an overview of the occurrence of pollutants in fish caught in Estonian waters. The content of non-dioxin-like polychlorinated biphenyls (ndl PCBs), polybrominated diphenyl ethers (PBDEs), organic tin (OT) and perfluorocompounds (PFAS) are examined and discussed in the study. The results revealed that potentially higher content of organo-tin compounds, perfluorocompounds and polybrominated diphenyl ethers in Baltic herring, salmon and river lamprey may cause concern regarding human exposure.

It is important to link pollutant content to lipid content of fish taking into account their seasonal variation in different age classes.

Leili Järv, Hannu Kiviranta, Jani Koponen and al., Journal of Marine Systems, Volume 171, July 2017, Pages 129–133

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Abundance and composition of near surface microplastics and plastic debris in the Stockholm Archipelago, Baltic Sea

We collected plastic debris in the Stockholm Archipelago using a manta trawl, and additionally along a transect in the Baltic Sea from the island of Gotland to Stockholm in a citizen science study. The samples were concentrated by filtration and organic material was digested using hydrogen peroxide. Suspected plastic material was isolated by visual sorting and 59 of these were selected to be characterized with Fourier transform infrared spectroscopy. Polypropylene and polyethylene were the most abundant plastics identified among the samples (53% and 24% respectively). We found nearly ten times higher abundance of plastics near central Stockholm than in offshore areas (4.2 × 105 plastics km−2 compared to 4.7 × 104 plastics km−2). The abundance of plastic debris near Stockholm was similar to urban areas in California, USA, and the overall abundance in the Stockholm Archipelago was similar to plastic abundance reported in the northwestern Mediterranean Sea.

Berit Gewert, Martin Ogonowski, Andreas Barth, Matthew MacLeod, Marine Pollution Bulletin, Vol. 120 (1-2), 15 July 2017

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Anthropogenic fibres in the Baltic Sea water column: Field data, laboratory and numerical testing of their motion

Distribution of microplastics particles (MPs) in the water column is investigated on the base of 95 water samples collected from various depths in the Baltic Sea Proper in 2015–2016. Fibres are the prevalent type of MPs: 7% of the samples contained small films; about 40% had (presumably) paint flakes, while 63% contained coloured fibres in concentrations from 0.07 to 2.6 items per litre. Near-surface and near-bottom layers (defined as one tenth of the local depth) have 3–5 times larger fibre concentrations than intermediate layers. Laboratory tests demonstrated that sinking behaviour of a small and flexible fibre can be complicated, with 4-fold difference in sinking velocity for various random fibres’ curvature during its free fall. Numerical tests on transport of fibres in the Baltic Sea Proper were performed using HIROMB reanalysis data (2007) for the horizontal velocity field and laboratory order-of-magnitude estimates for the sinking velocity of fibres. The model takes into account (i) motion of fibres together with currents, (ii) their very slow sinking, and (iii) their low re-suspension threshold. Sensitivity of the final distribution of fibres to variations of those parameters is examined. These experiments are the first step towards modelling of transport of fibres in marine environment and they seem to reproduce the main features of fibres distribution quite well.

A. Bagaev, A. Mizyuk, L. Khatmullina, I. Isachenko, I. Chubarenko, Science of The Total Environment, Volumes 599–600, 1 December 2017, Pages 560–571

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Bioturbation transports secondary microplastics to deeper layers in soft marine sediments of the northern Baltic Sea

Microplastics (MPs) are observed to be present on the seafloor ranging from coastal areas to deep seas. Because bioturbation alters the distribution of natural particles on inhabited soft bottoms, a mesocosm experiment with common benthic invertebrates was conducted to study their effect on the distribution of secondary MPs (different-sized pieces of fishing line < 1 mm). During the study period of three weeks, the benthic community increased MP concentration in the depth of 1.7–5.1 cm in the sediment. The experiment revealed a clear vertical gradient in MP distribution with their abundance being highest in the uppermost parts of the sediment and decreasing with depth. The Baltic clam Macoma balthica was the only study animal that ingested MPs. This study highlights the need to further examine the vertical distribution of MPs in natural sediments to reliably assess their abundance on the seafloor as well as their potential impacts on benthic communities.

Pinja Näkki, Outi Setälä, Maiju Lehtiniemi, Marine Pollution Bulletin, Volume 119, Issue 1, 15 June 2017, Pages 255–261

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