Optimising the frequency of clean-up actions in depositional coves in the Lofoten archipelago, Norway to maximize debris removal

Abstract

Marine litter is a global environmental problem which harms a vast amount of species and poses negative economic consequences. Five percent of the marine litter concentrates on the coastlines with an average concentration of 2000 kg per km2. For removing marine litter already present in the ocean, beach cleaning is highly efficient. The ocean is a dynamic system and previous studies have shown that daily clean-up actions gives ten times the amount of litter compared to monthly sampling. Therefore, the interval of beach cleaning is crucial if the goal is to remove as much marine waste as possible. This study conducted in total 117 clean-up actions between December 2017 and June 2018 in ten beaches in the Lofoten Archipelago, Norway and found that the optimal cleaning frequency is very site dependent, however all sites showed decreasing estimated daily accumulation rates with increasing clean-up intervals, meaning the rate of loss and resuspension to the surrounding environment is large. There were large variations in the accumulation from site to site, and 96 % of the 5970 items collected were plastic materials. The study also investigated whether the beach litter would stabilise and at the same time create a point in which a clean-up action would be favourable and if the average item weight varies with clean-up interval, however there were no clear results. Future studies are recommended to focus more on the impact of weather conditions to deepen our understanding of the dynamics of marine litter.