The Distribution of Microplastics in Salt Marshes

Grover, Benjamin (2024) The Distribution of Microplastics in Salt Marshes. Doctoral thesis, University of East Anglia.

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Abstract

Microplastics are becoming widely recognized as an increasing pollutant, found in all studied ecosystems with potential impacts to fauna, flora, and the general environment. However, salt marsh ecosystems remain largely understudied. This thesis presents a series of projects designed to measure microplastic abundance in two European salt marshes, whilst studying the spatial and temporal distribution of microplastics, and the factors affecting these patterns.

Firstly, method development was carried out to determine the most effective procedures for salt marsh sediments. The consequent methodology incorporates extraction using sediment-microplastic isolation (SMI) units, digestion using KOH: NaClO, identification using Nile Red staining, and analysis using micro-FTIR spectroscopy.

Secondly, sediment samples from Blakeney Point salt marsh were collected to study abundance and spatial distribution of microplastics. Microplastics were present in all samples from the marsh, averaging 21,216.68 ± 2,259.54 particles/m2 (3,429.94 ± 387.82 particles/kg d.w.). Vegetation zonation was observed to impact distribution, with samples in the Lower/Mid zone having over twice as many microplastics as any other zone. However, when considering the factors vegetation height, elevation and distance from the salt marsh edge, only vegetation height was found to have a significant correlation with microplastic abundance, and none were found to have any observable trends with the distribution of microplastics.

Lastly, sediment samples from a salt marsh in the Wadden Sea were used to determine temporal variability of microplastics over the past 60 years. Values found ranged from 8,486.56 – 74,257.43 particles/m2 (472.44 – 9,615.39 particles/kg d.w.), and 1,414.43 – 20,509.19 particles/m2 (160.64 – 1,836.16 particles/kg d.w.), with a general trend of microplastics decreasing with depth and time. However, unexpected values were found at certain depths in each core, perhaps relating to changes in vegetation coverage. A significant relationship for microplastics and sediments was found, based on their shared size fractions. Despite this, end-member determined sediment depositional processes could not be used to explain microplastic abundance.

Overall, microplastics were present in all samples from both salt marshes. Vegetation was found to have a key role in microplastic distribution, with vegetation zonation having impacts both spatially and temporally.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Chris White
Date Deposited:	03 Nov 2025 11:35
Last Modified:	03 Nov 2025 11:35
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100874
DOI:

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