| Abstract [eng] |
It is important to implement harmonized beach litter monitoring methods to allow comparability of results. However, frequently used methods, such as the OSPAR method for beach macro-litter (>25 mm) monitoring, were shown to be less suitable for Baltic Sea region due to its focus on rural and undisturbed beaches, which are rare in the Baltic Sea, and its tendency to underestimate smaller litter (<25 mm). To overcome these weaknesses six methods to examine meso-litter (5–25 mm) and large micro-litter (2–5 mm) were developed and tested at Baltic Sea beaches. Four of these methods, investigating flood accumulation zones and beach wrack were less practical because they were not regularly repeatable. Further, the pollution in the flood accumulation zone was highly irregular. Therefore, results were difficult to compare and to extrapolate, and this is hampering long-term trend analysis. A developed frame method was discarded as it only partly investigated the backshore, and surveys were too time intensive. A tested sand rake method, investigating the whole backshore of the beach, turned out to be useful, reliable, and fits within monitoring requirements of the Marine Strategy Framework Directive. In more than 200 sand rake surveys carried out around the Baltic Sea, a total of 9,345 litter pieces were found, on 10,271 m², of which 69.9% were 2–25 mm in size. Plastic (4,921 pieces) was the predominant material found (mean 52.7% ± 13.3). Abundance of litter was 0.91 pieces/m² ± 1.50 (median 0.40 pieces/m²). Results of the Baltic-wide campaign can be used for calculating a pollution baseline, defining the Good Environmental Status for smaller litter (2–25 mm) and can serve for assessing the effectiveness of marine litter mitigation measures in the Baltic Sea region. |
