The Long-Term Effects of Microfibers on the Ecosystem Services Performed by Marine Bivalves

The ecosystem services performed by bivalves are invaluable for the healthy functioning of coastal ecosystems. Through biofiltration, they control phytoplankton abundance and composition, and contribute to nutrient recycling. Consecutively, they diminish the detrimental effects of coastal eutrophication and Harmful Algal Blooms on water quality, fisheries and aquaculture.

Microplastic pollution can have a direct effect to organisms but potentially can also have indirect impacts by disrupting the ecosystem services performed by marine organisms. Specifically, research shows that ingestion and accumulation of microplastics by bivalves results in physiological and reproductive impairments with little evidence on possible impact on filtration capacity. Moreover, most research has focused on plastic fragments like microbeads and polystyrene with limited attention to microfibers - the most dominant microplastic in the marine environment. Additionally, there is still uncertainty on the long-term implications to the ecosystem functions performed by bivalves.

In this study we investigate the effects of microfiber accumulation on the capacity of the mussel Mytilus edulis to clear the water column from bloom concentrations of microalgae. We conducted a long-term experiment whereby mussels were exposed, for 52 days, to microfibers presence and microfibers absence treatments.

The microalgae clearance from the water column was significantly lower when exposed to microfibers in comparison to the microfiber absence treatment and this effect was noted after 26 days of experimentation. Based on a preliminary analysis of data, a potential mechanism for this effect is the increasing accumulation of microfibers within the digestive gland of the mussels.

Findings from this experiment will help us understand and quantify the impact of microfiber pollution on the capacity of ecosystems to remediate other environmental stressors such as coastal eutrophication. Therefore, results from this analysis should feed into policies regarding microfiber regulation into coastal systems.