Ecotoxicological risk assessment of microplastics in marine Arctic environment

Saeed, Mohammad Sadiq (2023) Ecotoxicological risk assessment of microplastics in marine Arctic environment. Masters thesis, Memorial University of Newfoundland.

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Abstract

The last few decades have witnessed an exponential increase in plastic production and consumption. The inexorable increase in microplastic accumulation, particularly in the Arctic waters, has become a major environmental concern. Discarded plastics degrade in the environment due to natural forces like wind, waves, and heat into smaller pieces. Plastic fragments produced or decomposed into a size range of 1 μm to 5 mm diameter are termed microplastics. Plastic debris travels through various environmental media before eventually reaching the oceans. In the various oceans, they travel along oceanic currents reaching the Arctic, where they get trapped in the Arctic ice. Moreover, local maritime operations like fishing, tourism, shipping, hydrocarbon exploration, and aquaculture also contribute to the microplastic accumulation in the Arctic waters. Microplastics are a complex group of pollutants containing plastic polymer, various stabilizing chemicals intentionally added during their production process and numerous other chemicals sorbed while being in the environment owing to their high surface area. These chemicals collectively enhance the toxicity of microplastics. The omnipresent microplastics possess characteristics such as toxicity, long-range mobility, bioaccumulative nature, and environmental persistence. The interaction of such an intricate pollutant like microplastic in the intriguing Arctic environment characterized by a ubiquitous sea-ice presence, extreme light regime, and unique species dwelling in makes them a serious threat to the Arctic marine ecosystem and the biota inhabiting it. Despite the pressing nature of this concern, there is a paucity of literature on microplastics and a dearth of research on investigating the associated risk. The work presented here assesses the risk posed by microplastics in the pristine and sensitive Arctic region. This thesis comprises two main contributions. Firstly, it develops an ecotoxicological risk model in polar cod (Boreogadus saida), a pivotal species of the Arctic food web, due to microplastic ingestion. Secondly, it assesses the human health risk due to microplastic prevalence in the Arctic waters. People dependent on the food sources from the Arctic ecosystem, mainly the indigenous people living in the remote Arctic communities, are exposed to higher risk due to limited medical resources and weaker immune systems. The study first identifies all the factors affecting microplastic intake in the polar cod and humans in the Arctic region. Then the response induced is ascertained. Subsequently, Bayesian Network, a probabilistic graphical modeling technique, is employed to assess ecotoxicity. The study will augment the understanding of the interaction of microplastic with the environment. Further, it will enhance the understanding of ecotoxicological risks in marine life and humans associated with microplastic ingestion. This study will also aid in the development of more effective risk management strategies and policies.

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