Monitoring methods for large micro- and meso-litter and applications at Baltic beaches

To complement existing micro-, meso and macro-litter monitoring strategies at sandy beaches, two user-friendly methods were further-developed and tested. The Rake-method and the Frame-method focus on large-micro (>2 mm) and meso-litter (5–25 mm) in the 30–50 mm upper sediment layer and were applied at 58 surveys at 15 sandy beaches of the German and Lithuanian Baltic Sea coast between 2014 and 2016. The Rake-method investigates sandy sediments to a depth of up to 50 mm. In average, we found 2.6 items / m² in Germany (65% micro and meso-litter) and 0.6 items / m² in Lithuania (66% micro and meso-litter). Using the Frame-method, covering the upper 30 mm, we received 1.8 items / m² in Germany (64% micro and meso-litter) and 5.3 items / m² in Lithuania (86% micro and meso-litter). Mostly found were cigarette butts, artificial polymers and in Lithuania paraffin. To test the reliability of both methods, recovery experiments were carried out. Depending on color and structure between 31 and 100% of all items were recovered by the Frame-method and 31–77% by the Rake-method. Using the Matrix Scoring Technique, tourism was identified as major pollution source. Both methods turned out to be suitable for sandy beaches, even if they are regular cleaned, and to assess pollution hot-spots. Both methods do not require elaborated equipment or a laboratory, are low in costs and can be carried out by volunteers. In comparison, the Rake method turned out to be more robust and cost-effective.