| dc.description.abstract | Microplastic (MP, < 5 mm) has become an omnipresent environmental pollutant due to inappropriate management since the invention of plastic during the 1800s. MPs are now detected in all environmental matrices, with marine sediments considered the final repository for MPs. The aim of this thesis was to present a comprehensive investigation of global concentrations and characteristics of MP pollution in sediment and biota in marine coastal areas. This thesis used a systematic review approach to summarise global MP concentrations and characteristics such as polymer composition, morphology, size, and colour from 92 research articles on MP in sediment and 46 publications on MP ingestion by marine organisms. A critical evaluation of sampling, processing, and analysis methodologies was conducted from the literature on MP pollution in sediment. In addition, an empirical study quantified MP concentrations and characteristics from marine coastal sediment in Kristiansand, southern Norway. Lastly, patterns of MP pollution in the above-mentioned matrices were discussed.
Unharmonized sampling, processing, and analysis methodologies were detected across articles. This highlighted the differences in abilities for extraction and detection of MP in the included studies, which imposed challenges for comparability between studies. Despite this, sediment globally and in southern Norway were found to be heavily polluted with MPs. Highest MP ingestion rates were found in organisms residing on the seafloor and in omnivores and filter feeders. MP characteristics displayed similar trends across the three studies. Small fibres and fragments under 1 mm in size were detected in highest abundance. The most frequently occurring polymers were polyethylene, polypropylene, and polyurethane.
The high MP concentrations in sediment evidences the role of marine sediment as MP sinks. High MP pollution in sediment increases the bioavailability of MPs for ingestion, hence the elevated ingestion rates in epifauna. Further, the MP polymer composition reflects the high production and discard rate of the polymers frequently applied in short lifecycle products. This thesis contributes to the global efforts to quantify MP pollution levels in sediment and biota globally, and its findings may facilitate evidence-based decision-making when further establishing of monitoring and management strategies. | |