Marte Haave, Tiril Klunderud and Anders Goksoyr
Increased production and use of plastics over the past decades has led to large volumes of plastic reaching the oceans. Some of this plastic is in the form of microplastic fragments (<5 mm), globally present from beaches to deep ocean basins. The dispersal pattern of microplastic is poorly known, but the ocean floor is a likely sink. Benthic fauna has been found to be exposed, which is a potential re-entry of microplastics and associated chemicals into the food-web.
Marine litter is addressed through UN programs and EU frameworks. At present the EU Water Framework Directive (WFD) does not address micro-litter, while the EU Marine Strategy Framework Directive does. Norway has committed to address the issue of marine litter and micro-litter to document the environmental status, implying that Norway must build competence to monitor microplastics along the long Norwegian coastline. Uni Research has carried out standardized marine monitoring since the 70’s, and has in-depth knowledge about the biological, hydrographic and chemical conditions in the marine ecosystems near Bergen. International expert groups have advised to start investigating microplastic occurrence and effects in such well-known eco-systems in order to rapidly fill the knowledge gap. We have therefore started quantifying microplastics in sediment and biota, in a gradient from the discharge sites for untreated sewage to the deep hollows in the urban Byfjorden in Bergen, Norway. Data from sediments will be used to refine an existing 3D-hydrodynamic fjord model adapted to microplastics, for predicting microplastic dispersal. Knowledge of levels in biota and environmental distribution is essential for realistic assessment of environmental effects, and to improve monitoring methods. Preliminary findings show colored fibers in some species of polychaeta at the investigated discharge points and the deep sites in the urban fjord after NaOH digestion followed by vacuum-filtration (5-12µm). The results indicate ingestion of fibers only in certain species. Both size and feeding habits seem likely to affect uptake in polychaetes. The investigation of benthic fauna might be a cost-efficient option for monitoring environmental microplastic pollution.
The observed quantities of microplastics in sediment and biota will be compared to a 3D-hydrodynamic fjord model, adapted to microplastic dispersal, which will serve as a guide for targeted sampling once fully developed. Such knowledge is essential for future efficient investigation of the environmental levels of microplastics. Knowledge of the main sources and expected hotspots will also be valuable tools for taking mediating actions, and for realistic assessments of environmental effects.