Description: The discovery of atmospheric micro(nano)plastic transport and ocean–atmosphere exchange points to a highly complex marine plastic cycle, with negative implications for human and ecosystem health. Yet, observations are currently limited. In this Perspective, we quantify the processes and fluxes of the marine-atmospheric micro(nano)plastic cycle, with the aim of highlighting the remaining unknowns in atmospheric micro(nano)plastic transport. Between 0.013 and 25 million metric tons per year of micro(nano)plastics are potentially being transported within the marine atmosphere and deposited in the oceans. However, the high uncertainty in these marine-atmospheric fluxes is related to data limitations and a lack of study intercomparability. To address the uncertainties and remaining knowledge gaps in the marine-atmospheric micro(nano)plastic cycle, we propose a future global marine-atmospheric micro(nano)plastic observation strategy, incorporating novel sampling methods and the creation of a comparable, harmonized and global data set. Together with long-term observations and intensive investigations, this strategy will help to define the trends in marine-atmospheric pollution and any responses to future policy and management actions.

Description: The discovery of atmospheric micro(nano)plastic transport and ocean–atmosphere exchange points to a highly complex marine plastic cycle, with negative implications for human and ecosystem health. Yet, observations are currently limited. In this Perspective, we quantify the processes and fluxes of the marine-atmospheric micro(nano)plastic cycle, with the aim of highlighting the remaining unknowns in atmospheric micro(nano)plastic transport. Between 0.013 and 25 million metric tons per year of micro(nano)plastics are potentially being transported within the marine atmosphere and deposited in the oceans. However, the high uncertainty in these marine-atmospheric fluxes is related to data limitations and a lack of study intercomparability. To address the uncertainties and remaining knowledge gaps in the marine-atmospheric micro(nano)plastic cycle, we propose a future global marine-atmospheric micro(nano)plastic observation strategy, incorporating novel sampling methods and the creation of a comparable, harmonized and global data set. Together with long-term observations and intensive investigations, this strategy will help to define the trends in marine-atmospheric pollution and any responses to future policy and management actions.

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: Plastic pollution has become ubiquitous with very high quantities detected even in ecosystems as remote as arctic sea ice and deepsea sediments. Ice algae growing underneath sea ice are released upon melting and can form fast-sinking aggregates. In this pilot study, we sampled and analyzed the ice algaeMelosira arcticaand ambient sea water from three locations in the Fram Strait to assess their microplastic content and potential as a temporary sink and pathway to the deep seafloor. Analysis by μ-Raman and fluorescence microscopy detected microplastics (≥2.2 μm) in all samples at concentrations ranging from 1.3 to 5.7 × 104 microplastics (MP) m−3 in ice algae and from 1.4 to 4.5 × 103 MP m−3 in sea water, indicating magnitude higher concentrations in algae. On average, 94% of the total microplastic particles were identified as 10 μm or smaller in size and comprised 16 polymer types without a clear dominance. The high concentrations of microplastics found in our pilot study suggest thatM. arctica could trap microplastics from melting ice and ambient sea water. The algae appear to be a temporary sink and could act as a key vector to food webs near the sea surface and on the deep seafloor, to which its fast-sinking aggregates could facilitate an important mechanism of transport.