Anthropogenic impact: Marine litter

Marine litter. Photo: Geir Wing Gabrielsen, Norwegian Polar Institute

Pollution 2018
Typography
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Marine litter is defined as “any persistent, manufactured or processed solid material discarded, disposed or abandoned in the marine and coastal environment”. Large-scale monitoring of marine litter was conducted by the BESS survey during the 2010–2017 period, and helped to document the extent of marine litter in the Barents Sea (the BESS survey reports, Grøsvik et al., 2018). Distribution and abundance of marine litter were estimated using data from: pelagic trawling in upper 60 m; trawling close to the seabed; and visual observations of floating marine debris at surface.

The study, done by Grøsvik et al., 2018, had comprehensive, with data collected from 2265 pelagic trawls and 1860 bottom trawls, and surface observations made between stations. Marine litter was recorded from 301 pelagic- and 624 bottom-trawl catches. In total, 784 visual observations of floating marine debris were recorded during the period. Marine litter was categorized according to volume or weight of material type: plastic; wood; metal; rubber; glass; paper; or textile. Marine litter is observed in the entire Barents Sea and distribution varied with material densities, ocean currents, and water depth. Plastic was the dominant type of marine litter observed at: 72% of surface observations; 94% of pelagic trawl stations; and 86% of bottom-trawl stations (Figure 3.9.6.1.1, Grøsvik et al., 2018). Wood constituted 19% of marine litter observed at the surface, 1% in pelagic trawls, and 17% in bottom trawls. Materials from other categories — metal, rubber, paper, textile, and glass — were observed less frequently.

Floating marine debris was widely distributed; highest volume was observed in central, eastern, and northern areas (Figure 3.9.7.1). Wood dominated observations in this category (61.9 ±21.6% by volume), while plastic constituted 34.6 ±22.3% by volume. Metal, rubber, and paper were recorded less frequently.

Pelagic marine litter was observed in 13% of all pelagic trawls with a mean of 58 grammes per trawl catch, and was widely distributed (Figure 3.9.7.1). Plastic formed the bulk (85.1%) of pelagic marine litter observed with a mean of 0.011 mg m-3; paper formed 9.4%; textile formed 3.9%, and was more seldom observed; other materials were only observed sporadically. Pelagic plastic was significantly correlated with latitude and longitude during some years, and indicated northeastern distribution in 2010, and northern distribution in 2011 and 2014.

Marine litter as bycatch from bottom trawling was observed in 33.5% of all bottom-trawl hauls, with a mean of 772 g per haul. Marine litter from bottom trawls was distributed widely; highest levels were observed in western, southeastern, north eastern parts, and around Svalbard. Plastic was observed in the entire Barents Sea, processed wood in eastern and northern parts, and metal and rubber in the southeast (Figure 3.9.7.1 and 3.9.7.2). Processed wood dominated marine litter from bottom trawls, with 66% of mean weight in all catches with any type of marine litter. Plastic constituted 11.4% of the mean weight; but dominated in the number of observations. Metal and rubber constituted ~10% of the mean weight, but the number of observations was limited. On average, 26 kg km−2 of marine litter was observed in the Barents Sea; with an average of 2.9 kg km−2 of plastic litter alone (Grøsvik et al., 2018).

Current situation and trends

The Russian Zone was not well covered during the 2018 BESS. As result, only maps of anthropogenic marine litter distribution in the observed area are presented without comparison to previous years or estimation of average weight of litter observed in trawls.
Plastic dominated types of anthropogenic litter observed at the water surface and in both pelagic and bottom trawls (Figure 3.9.7.1, 3.9.7.2).

Figure 3.9.7.1 Types of anthropogenic marine litter (m3) observed at the surface during the 2018 BESS . From the 2018 BESS Report (Prokhorova and Grøsvik, 2019).Figure 3.9.7.1 Types of anthropogenic marine litter (m3) observed at the surface during the 2018 BESS . From the 2018 BESS Report (Prokhorova and Grøsvik, 2019).

Figure 3.9.7.2 Types of anthropogenic marine litter collected in pelagic trawls (left) and bottom trawls (right). Size of circles indicate weight in the range of >0, >100g, and >200 g for pelagic trawls or in the range of >0, >1000 g and >4000 g for bottom trawls. Crosses indicate trawl stations. From the 2018 BESS Report (Prokhorova and Grøsvik, 2019).Figure 3.9.7.2 Types of anthropogenic marine litter collected in pelagic trawls (left) and bottom trawls (right). Size of circles indicate weight in the range of >0, >100g, and >200 g for pelagic trawls or in the range of >0, >1000 g and >4000 g for bottom trawls. Crosses indicate trawl stations. From the 2018 BESS Report (Prokhorova and Grøsvik, 2019).

The number of litter recordings from both pelagic and bottom stations has increased during the period since these recordings were initiated (2010) through 2018. In 2010, 6.6 % of pelagic trawls contained litter, 2.9 % in 2011, and 24.2 % in 2018 (Figure 3. 10.7.3). Litter recordings in bottom trawls were 10.9 % in 2010 and 54.0 % in 2018) (Figure 3.9.6.3).

Figure 3.9.7.3 Number of stations (%) with anthropogenic litter collected in  pelagic trawl stations (left) and bottom trawl stations (right) during the BESS from 2010 through 2018.Figure 3.9.7.3 Number of stations (%) with anthropogenic litter collected in pelagic trawl stations (left) and bottom trawl stations (right) during the BESS from 2010 through 2018.

We observed distribution of different types of anthropogenic marine litter during the two periods: 2010-2013 and 2013-2018 (Figure 3.10.7.4). Plastics dominated all types of litter in pelagic and bottom trawl stations both during the 2010-2013 and 2014-2018 periods. Plastic constituted 94.7 % of marine litter content in pelagic trawls during the 2010-2013 period and 95.6 % during 2014-2018. For bottom trawls, 81.0 % of litter recorded was plastic during the 2010-2013 period, while 88.7 % of litter recorded contained plastic during 2014-2018. Litter from fisheries — ropes, strings and cords, pieces of nets, floats/buoys, etc. — dominated recordings of plastic litter. Wood was recorded as bycatch from bottom stations, mainly in northern and eastern regions of the Barents Sea. The number of bottom stations with wood was lower during the 2010-2013 period (11.3 % of stations) compared with the 2010-2013 period (19.0 % of stations). Metal, paper, rubber, glass, and textiles were all observed sporadically in both pelagic and bottom trawl catches.

Figure 3.9.7.4 Types of anthropogenic marine litter collected in pelagic trawl stations (left) and bottom trawl stations (right) during the 2010-2013 period (upper) and the 2014-2018 period (lower).Figure 3.9.7.4 Types of anthropogenic marine litter collected in pelagic trawl stations (left) and bottom trawl stations (right) during the 2010-2013 period (upper) and the 2014-2018 period (lower).

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