Improving ecological function of polluted coasts under a tide of plastic waste

Abstract

Unprecedented levels of plastics are entering coastal seas, which are already subject to another insidious pollutant: excess nitrogen. Both pollutants were created to enhance human well-being on land but once in the sea they impair the function of filter-feeding organisms that help maintain coastal water quality. We conceptualized evidence to show that oysters (Ostrea spp), the reefs of which can provide a biological solution for managing water quality, can effectively reduce the threat of algal blooms caused by excess nitrogen pollution, even when exposed to moderate microplastic pollution. Yet the functional collapse of this ecosystem service (filter-feeding by oysters) is at risk if current trends in plastic pollution continue, and pollution thresholds that predict functional collapse have already been exceeded in the world's most polluted rivers. Nevertheless, although the plastic problem is daunting, growing social and political awareness of the need to reduce plastic waste provides hope that a sustainable material society can be attained.