Abstract
Microfibers (MF) are one of the major classes of microplastic found in the marine environment on a global scale. Very little is known about how they move and distribute from point sources such as wastewater effluents into the ocean. We chose Adventfjorden near the settlement of Longyearbyen on the Arctic Svalbard archipelago as a case study to investigate how microfibers emitted with untreated wastewater will distribute in the fjord, both on a spatial and temporal scale. Fiber abundance in the effluent was estimated from wastewater samples taken during two one-week periods in June and September 2017. Large emissions of MFs were detected, similar in scale to a modern WWTP serving 1.3 million people and providing evidence of the importance of untreated wastewater from small settlements as major local sources for MF emissions in the Arctic. Fiber movement and distribution in the fjord mapped using an online-coupled hydrodynamic-drift model (FVCOM-FABM). For parameterizing a wider spectrum of fibers from synthetic to wool, four different density classes of MFs, i.e., buoyant, neutral, sinking, and fast sinking fibers are introduced to the modeling framework. The results clearly show that fiber class has a large impact on the fiber distributions. Light fibers remained in the surface layers and left the fjord quickly with outgoing currents, while heavy fibers mostly sank to the bottom and deposited in the inner parts of the fjord and along the northern shore. A number of accumulation sites were identified within the fjord. The southern shore, in contrast, was much less affected, with low fiber concentrations throughout the modeling period. Fiber distributions were then compared with published pelagic and benthic fauna distributions in different seasons at selected stations around the fjord. The ratios of fibers to organisms showed a very wide range, indicating hot spots of encounter risk for pelagic and benthic biota. This approach, in combination with in-situ ground-truthing, can be instrumental in understanding microplastic pathways and fate in fjord systems and coastal areas and help authorities develop monitoring and mitigation strategies for microfiber and microplastic pollution in their local waters.
Highlights
Microplastic fibers (MF) are major constituents of microplastic pollution in the aquatic environment
Our data indicate that total yearly emissions of fibers into the Adventfjord from wastewater effluent amount to about 18 billion non-white MF of the size 0.05–5 mm
450 mg fibers can be released during an average washing machine cycle containing three pieces of clothing, which can be recalculated to 744 × 103 microfibers from one washing machine run alone (Cole et al, 2020; Napper et al, 2020)
Summary
Microplastic fibers (MF) are major constituents of microplastic pollution in the aquatic environment. The effects of MF on marine biota are not well known but can include entanglement and ingestion, which in turn may affect their physiology and reproductive success (Cole et al, 2015). Transformation processes such as environmental degradation (weathering) and biofouling alter the plastic surface, buoyancy, and colonization with microbes (biofouling) and can increase microplastic ingestion rates (Vroom et al, 2017; Welden and Cowie, 2017; Bra°te et al, 2018). New data are needed to map spatial and temporal overlap between microplastics in general, and MF in particular, and marine biota to predict geographic areas where potential effects are likely to occur
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