An exploratory analysis of seabed litter dynamics in the SE German Bight.

The accumulation of marine litter on coastal seabeds is influenced by various anthropogenic and environmental factors. To identify litter accumulation areas on the seafloor, it is necessary to understand the interaction of these parameters. This study analyses the seafloor litter occurrence in the southeastern North Sea, based on samples collected between October 2017 and March 2019. Litter data were combined with hydrographic, high-resolution in situ measurements and further geographic as well as anthropogenic factors for statistical analyses. Benthic litter showed a mean density of 2473 ± 3116 items km-2, and plastics consisting mainly of fisheries-related items represented the majority of identified objects. The statistical analyses suggest that salinity and temperature gradients, the meridional bottom currents, as well as the distance of the station to the coastline have a significant effect on benthic litter abundance. Direct combination of litter sampling and hydrographic measurements can improve the understanding of seabed litter dynamics.

Trashing our own "backyard" - Investigating dispersal and accumulation of floating litter from coastal, riverine, and offshore sources in the German Bight using a citizen science-based wooden drifter recapture approach.

Understanding marine debris dispersal through drift buoys and numerical modelling is one focus of litter pollution research that can identify particularly affected regions and aid targeted clean-up efforts. This study assessed the dispersal and accumulation of floating litter from coastal, riverine, and offshore sources in the German Bight, based on ~33,000 reports of wooden drifters deployed between 2016 and 2019. The majority (66.6%) released along the Lower Saxony coast and the rivers Ems, Weser, and Elbe were first reported within ≤25 km, indicating that coastal and riverine litter sources largely pollute adjacent shorelines. Drifters from coastal sites and release points near the river mouths dispersed similarly far, occasionally crossing distances comparable to those deployed at sea, reaching Scandinavia and Great Britain within a few days or weeks. Small-scale clustering occurred in <2% of all locations where drifters had been reported. These findings and limitations of the methodological approach are discussed.

Wasting the North Sea? - A field-based assessment of anthropogenic macrolitter loads and emission rates of three German tributaries.

Research into the scope of litter pollution in freshwater systems has shown similar levels to the marine and coastal environment. Global model estimates of riverine emission rates of anthropogenic litter are largely based on microplastic studies as long-term and holistic observations of riverine macroplastics are still scarce. This study therefore aims to contribute a detailed assessment of macrolitter in the transitional waters of three major North Sea tributaries: Ems, Weser, and Elbe. Litter surveys were carried out in four river compartments: along the embankment, on the river surface, in the water column, and on the river bed. The data revealed spatio-temporal variability and distinct pollution levels for each compartment. Beaches had the highest debris diversity and were significantly more littered than vegetated sites and harbors. Stony embankments were least polluted. Benthic litter levels appeared substantial despite rapid burial of objects being likely due to high suspended sediment loads. Two extrapolation approaches were tested to scale daily and annual litter emission quantities of surface- and subsurface-floating litter. Using the mean (median) litter item mass from water column samples, total annual mass discharges were calculated: ∼0.9 (0.2) t y-1 to ∼2.8 (0.5) t y-1 emitted via the Ems, ∼1.3 (0.2) t y-1 to ∼12.0 (1.9) t y-1 through the Weser, and ∼14.7 (2.4) t y-1 to ∼801 (128) t y-1 carried into the North Sea by the Elbe. These rates deviate considerably from previous model estimates of plastic loads discharged by these three rivers. Future studies should therefore ground-truth model estimates with more river-specific and long-term field observations. Overall, the estimated plastic debris discharge quantities account for <1% of the total mass of mismanaged plastic waste per catchment.

Wind, waves, tides, and human error? - Influences on litter abundance and composition on German North Sea coastlines: An exploratory analysis.

Being globally and locally prevalent, beach litter has been monitored at 29 sites along the German North Sea coastline. This study offers an exploratory analysis of data from 1991 to 2016. Schleswig-Holstein exhibited lower mean litter pollution levels than Lower Saxony, possibly because the locations in Lower Saxony are situated along the main coastal current, whereas the North Frisian Islands act as a barrier for the mainland sites in Schleswig-Holstein. Locations close to the Elbe estuary had significantly larger amounts of debris, likely receiving litter from marine and riverine sources. No clear overall pattern in litter abundance or composition could be detected. Significant quantitative similarities between debris types were inconsistent. The effect of wind, tides, and exposure appeared to be marginal. Recurring data inconsistencies, gaps, and outliers were partly attributed to human error. This could be reduced through hypothesis-driven monitoring with a simpler litter classification and continuous data checking.