T. Becker

Abstract
Accumulation of marine (plastic) debris from local land-based and distal marine-based sources along coastlines is a pressing modern issue. Hitherto, assessing the relative contribution of pollution sources through beach sur- veys is methodologically challenging. We surveyed ten beaches along the leeward and windward coastlines of Aruba (southern Caribbean) to determine differences in macro- and meso-debris densities. Differences were quantified using three metrics: 1) the gradient in macro-debris density away from the waterfront; 2) the propor- tion of plastic within macro-debris; 3) the meso-:macro-debris ratio. Overall 42,585 macro-debris items and 884 meso-debris items were collected. The density of near-shore macro-debris, proportion of plastic debris herein, and meso-:macro-debris ratio were highest on the windward coastline. These results suggest that southern Ca- ribbean windward coastlines are mainly exposed to debris originating from distal marine-based sources, and lee- ward coastlines to local land-based sources. Our metrics clearly reflect these differences, providing novel means to survey debris source origin.