Description: Floating marine debris is ubiquitous in marine environments but knowledge about quantities in remote regions is still limited. Here, we present the results of an extensive survey of floating marine debris by experts, trained scientists from fields other than pollution or non-professional citizen scientists. A total of 276 visual ship-based surveys were conducted between 2015 and 2020 in the Northeast (NE) Atlantic from waters off the Iberian Peninsula to the Central Arctic, however, with a focus on Arctic waters. Spatiotemporal variations among regional seas (Central Arctic, Barents Sea, Greenland Sea, Norwegian Sea, North Sea) and oceanic regions (Arctic waters and the temperate NE Atlantic) were explored. The overall median debris concentration was 11 items km-2, with considerable variability. The median concentration was highest in the North Sea with 19 items km-2. The Nordic seas, except the Central Arctic showed median concentrations ranging from 9 to 13 items km-2. Plastic accounted for 91% of all floating items. Miscellaneous fragments, films, ropes and nets, packaging materials, expanded polystyrene and straps were the most frequently observed plastic types. Although the median debris concentration in the Central Arctic was zero, this region was not entirely free of floating debris. The variations between regional seas and oceanic regions were statistically not significant indicating a continuous supply by a northward transportation of floating debris. The data show a slight annual decrease and clear seasonal differences in debris concentrations with higher levels observed during summer. A correlation between debris concentrations and environmental and spatial variables was found, explaining partly the variability in the observations. Pollution levels were 500 times lower than those recorded on the seafloor indicating the seafloor as a sink for marine debris. The Arctic was characterised by similar pollution levels as regions in temperate latitudes highlighting that Arctic ecosystems face threats from plastic pollution, which add to the effects of rapid climate change.

Description: In 1999 the AWI established the HAUSGARTEN observatory, to assess the impact of climate change on Arctic ecosystems in Fram Strait (Arctic), which included repeated camera transects to assess changes on the deep Arctic seafloor. A first analysis of the footage highlighted that marine debris increased over time. Plastic debris was also sighted during sea surface observations for seabird surveys. This prompted us to add a pollution observatory to the ongoing research programme FRAM, aiming to quantify plastic pollution in different ecosystem compartments to identify hidden sinks. Here, we summarise the results of this work encompassing matrices such as snow, sea ice, surface waters, water column, deep seafloor, biota and Arctic beaches. Images from the deep seafloor taken since 2002 showed a marine debris concentration of 4,571 ± 1,628 items km-2, which is in range with polluted oceanic regions. Visual surveys of floating debris from the same region revealed 500 times lower concentrations (9 items km-2), showing that the deep Arctic seafloor constitutes a sink for marine debris. Quantities of 9–483 g m-2 were reported from 15 beach surveys on Svalbard by citizen scientists. Plastics accounted for 〉80% of the mass, primarily from fisheries. Microplastics in samples from the sea surface, water column, sediment, sea ice and snow were analysed by combining state-of–the-art sampling technology with µFT-IR analyses. Using the same analysis for samples from different ecosystem compartments enabled us to determine the vertical distribution of microplastics, as sea ice entrains extremely high microplastic concentrations, which are released to the underlying waters during ice melts. In-situ pump-filtrations throughout the water column revealed that microplastics prevail at all depths in Fram Strait (0–1,287 items m–3). Microplastic concentrations in sediments ranged from 239–13,331 N kg–1. Highest microplastics concentrations in sediments and the water column were measured close to the marginal ice zone and polymer compositions indicated a sea ice origin for most particles found in the deep waters of East Greenland, indicating sea ice as a temporal sink. Indeed, the highest concentration (1.2 ± 1.4) ×107 items m-3) was recorded in an ice core from pack ice of Fram Strait. The presence of microplastic in snow samples from ice floes indicates atmospheric deposition of microplastics. Recent research shows that resident zooplankton ingests microplastics, which were also found in the ice algae Melosira arctica. The data indicate that the seafloor and sea ice constitute (temporal) sinks of plastic pollution and that pollution levels are high, despite of the distance to sources. The receding sea ice has already led to increased anthropogenic pressure in the Fram Strait, which is likely to become a major shipping lane during summer. The number of fishers operating around Svalbard and of ship calls to Longyearbyen has already increased significantly. In addition, the prevailing hydrography promotes the transport of plastic pollutants from distant sources, mostly from the Atlantic Ocean, but also from the Central Arctic via the Transpolar Drift. Long-range atmospheric transport and deposition likely adds to this.

Description: Die Be­las­tung un­se­rer Mee­re und Ozea­ne mit Müll ist ein Um­welt­pro­blem glo­ba­len Aus­ma­ßes. Es wird pro­gnos­ti­ziert, dass der jähr­li­che glo­ba­le Ein­trag von land­ba­sier­tem Kunst­stoff­müll von rund 8 Mil­lio­nen Ton­nen im Jahr 2010 auf bis zu 100–250 Mil­lio­nen Ton­nen im Jahr 2025 an­stei­gen wird. 99% al­ler See­vo­gel-Ar­ten sol­len bis 2050 Plas­tik­müll ver­zeh­ren, heute sind es bereits ca. 90%. Wir wis­sen mitt­ler­wei­le, dass hier ein Um­welt­pro­blem glo­ba­len Aus­ma­ßes ent­stan­den ist, das nicht nur die Na­tur be­droht, son­dern auch Aus­wir­kun­gen auf den Men­schen ha­ben wird. Zu den bio­lo­gi­schen Ef­fek­ten kom­men so­zio-öko­no­mi­sche Aus­wir­kun­gen, wie Ein­bu­ßen im Tou­ris­mus, aber auch die un­mit­tel­ba­re Be­schä­di­gung in­dus­tri­el­ler An­la­gen und Kos­ten durch See­notret­tung. Seit 1999 be­treibt das Al­fred-We­ge­ner-In­sti­tut Lang­zeit­un­ter­su­chun­gen am Tief­see-Ob­ser­va­to­ri­um HAUS­GAR­TEN in der Ark­tis. Re­gel­mä­ßig wie­der­hol­te Auf­nah­men mit ei­ner ge­schlepp­ten Ka­me­ra zei­gen, dass der Mee­res­grund der ark­ti­schen Tief­see seit 2002 im­mer mehr Müll be­her­bergt. Auch an den Strän­den Spitz­ber­gens wird mitt­ler­wei­le an­ge­schwemm­ter Müll ein­ge­sam­melt. Un­se­re Un­ter­su­chun­gen zei­gen, dass gro­ße Men­gen von Mi­kro­plas­tik in das Meer­eis, Schnee und die Se­di­men­te der Tief­see ge­langt sind. In die­sem Vor­trag wird ein Aus­blick über die Er­geb­nis­se ge­zeigt und die Ur­sa­chen dis­ku­tiert.

Description: Marine sublittoral sandbanks are essential offshore feeding grounds for larger crustaceans, fish and seabirds. In the southern North Sea, sandbanks are characterized by considerable natural sediment dynamics and are subject to chronic bottom trawling. However, except for the Dogger Bank, sandbanks in the southeastern North Sea have been only poorly investigated until now. We used an extensive, multi-annual dataset covering ongoing national monitoring programmes, environmental impact assessments, and basic research studies to analyse benthic communities on sublittoral sandbanks, evaluating their ecological value against the backdrop of similar seafloor habitats in this region. The analysis revealed complex spatial structuring of sandy seafloor habitats of the southeastern North Sea. Different infauna clusters were identified and could be specified by their composition of characteristic species. The sandbanks shared common structural features in their infauna community composition although they were not necessarily characterized by particularly high biodiversity compared to other sandy habitats. A close association of one of the main bioturbators in the southern North Sea, the sea urchin Echinocardium cordatum, with sandbanks was detected, which may promote the sediment-bound biogeochemical activity in this particular seafloor habitat. This would corroborate the status of sandbanks as sites of high ecological value calling for consideration in marine conservation.

Description: The German Bight (North Sea) is a centre of development of offshore wind energy. In the near future, windfarms will cover a significant part (about 25%) of the German Exclusive Economic Zone. In order to understand and assess potential effects of the construction and early operational phase of offshore wind turbines on the marine environment, an extensive research programme was carried out at Germany's first offshore windfarm alpha ventus. Here, data are presented on macroinfauna and local sediment characteristics collected as part of this programme. Grab samples were taken annually in autumn in 2008 (baseline), 2009 (construction phase) and 2010 and 2011 (early operational phase). Sampling stations were located along transects between adjacent turbines inside the windfarm and in two reference areas with similar environmental conditions in terms of sediment characteristics and water depth. A total of 336 samples were taken inside the windfarm and 192 samples in the reference areas. Sediment characteristics were described in terms of grain size distribution and organic content. The infauna was taxonomically analysed and quantified in terms of abundance and biomass. One-hundred three infauna taxa were identified, mainly belonging to the polychaetes, crustaceans and bivalves, living in fine to medium sandy soft bottom in water depths ranging from -27 m to -30 m. The data can be useful in meta-analyses of renewable energies impacts. Additionally, the data can support species distribution modelling to gain a better understanding of species' requirements and habitats as a basis for spatial planning scenarios and the evaluation of the ecological status of the marine environment. Moreover, the data can serve as baseline data for future monitoring and management of nearby protected areas where environmental conditions are comparable to those of the present study area.

Description: Microbial composition and diversity in marine sediments are shaped by environmental, biological, and anthropogenic processes operating at different scales. However, our understanding of benthic microbial biogeography remains limited. Here, we used 16S rDNA amplicon sequencing to characterize benthic microbiota in the North Sea from the top centimeter of 339 sediment samples. We utilized spatially explicit statistical models, to disentangle the effects of the different predictors, including bottom trawling intensity, a prevalent industrial fishing practice which heavily impacts benthic ecosystems. Fitted models demonstrate how the geographic interplay of different environmental and anthropogenic drivers shapes the diversity, structure and potential metabolism of benthic microbial communities. Sediment properties were the primary determinants, with diversity increasing with sediment permeability but also with mud content, highlighting different underlying processes. Additionally, diversity and structure varied with total organic matter content, temperature, bottom shear stress and bottom trawling. Changes in diversity associated with bottom trawling intensity were accompanied by shifts in predicted energy metabolism. Specifically, with increasing trawling intensity, we observed a transition toward more aerobic heterotrophic and less denitrifying predicted metabolism. Our findings provide first insights into benthic microbial biogeographic patterns on a large spatial scale and illustrate how anthropogenic activity such as bottom trawling may influence the distribution and abundances of microbes and potential metabolism at macroecological scales.

Description: The authors regret that the specified units of bioirrigation activity (Ic) and the indices (i.e. IPc,AFDM, IPc,WM, BPc,WM, BPc,AFDM) were incorrect in the original publication. Bioirrigation activity was presented in l/m25 min rather than in l/m2h and the indices were calculated per experimental core rather than per m2. Nevertheless, this does not affect the results and also the conclusions remain unchanged. AICc values for the best models of IPc,AFDM, IPc,WM, BPc,WM, BPc,AFDM have not changed in relation to each other, although they differ in value. The corrected version of Appendix B includes the corrected statistical details (i.e. AICc values). The corrected version of the Fig. 1 is provided below. The authors would like to apologize for any inconvenience caused.