Microlitter in arctic marine benthic food chains and potential effects on sediment dwelling fauna
Marine litter pollution affects oceans globally and has today also made its way to the pristine arctic environment adding to the microlitter from local pollution sources. Marine litter pollution is recognized as a serious threat to the marine environment at all levels, from the UN to regional (EU, OSPAR, HELCOM) and national authorities. The risk posed by microlitter to marine biota is related to their documented ubiquity and long residence time in marine ecosystems. Risks are also mediated by intrinsic toxicity of added chemicals and potential adsorbance of other pollutants. When released into the marine environment, a major part of microlitter likely accumulate in beach sand and marine sediments either immediately or after acquiring a biofilm. It is therefore expected that benthic food chains will be key to understanding fate and effects (i.e. concentrations, potential trophic transfer and biological impact) of microlitter in the marine environment. The overall aim of the project was to determine abundance of microlitter pollution in marine sediments and benthic food chains in the Arctic, and to evaluate the abundance in relation to potential local sources and background levels. The aim was also to investigate potential effects of microplastic pollution on benthic organisms through laboratory studies using an arctic amphipod as a model organism. The field investigations in Svalbard, Norway and Greenland focused on determining microlitter particle concentrations and characteristics in marine sediments and biota collected close to and far from potential local pollution sources and pathways, i.e. outlets of untreated wastewater and effluents from a dumping site in Sisimiut, West Greenland and outlets of treated (Ny-Ålesund) and untreated (Longyearbyen) wastewater in Svalbard. Overall, higher concentrations and a higher diversity of microlitter types and polymers were found in sediments and organisms (blue mussels and cod) closer to human settlements (wastewater outlets and dumping sites) and in places where lost and/or dumped fishing gear accumulate. Thus, we can confidently conclude that local pollution sources for anthropogenic microlitter do exist in the Arctic. The experimental studies investigated whether environmentally relevant and future predicted concentrations of microplastics could impact feeding rate, microplastic ingestion, respiration and locomotion activity in an arctic sediment dwelling amphipod. The experimental results confirm previous microplastics studies on marine invertebrates showing effect only at very high concentrations not yet relevant in the arctic environment. The shape of the plastic particles was found to affect the particle fate. While microplastic fragments were ingested, short microplastic fibres attached to the carapace of the amphipods and likely obstructed normal ventilation behaviour. Furthermore, biofilm cover was found to affect the behaviour and effects of the particles. Microlitter naturally become covered by biofilms in the environment and our results stress the importance of effect experiments being carried out using naturally fouled plastics for ecological relevance. This report provides both environmental- and impact data related to microlitter pollution in the arctic marine environment. Although the levels of microplastics required to cause effects in experimental organisms in this study were much higher than what was detected in the field, there may be other species that are more sensitive than the one tested in nature. The currently relatively low microlitter concentrations detected in the field should be considered as a “window of opportunity” to act to at least reduce local pollution. Consequently, introduction of sustainable waste management and wastewater treatment should be an important focus of local management initiatives.