The distribution and abundance of microplastic pollution in Northern Ireland’s freshwater ecosystems and their effect on macroinvertebrates

Abstract

Freshwater ecosystems are essential for life, offering drinkable water, vital nutrients through food, supporting economic avenues like fisheries, ensuring agricultural land fertility, and being a habitat for numerous species. However, they rank among the most polluted, especially with microplastics, tiny particles under 5mm. These microplastics adversely affect macroinvertebrates, vital for nutrient cycling and foundational to the food chain. Despite these concerns, there are currently no data available on microplastic pollution in Northern Ireland freshwater systems, which host several economically important fisheries. Data is urgently needed for this region to assess the risk microplastics pose to local macroinvertebrate communities and the essential ecosystem services they provide. This thesis addresses this by surveying NI’s loughs and rivers, estimating microplastics' impact on ecosystem services.

The surveys found that NI's freshwaters possess notably low microplastic contamination compared to global counterparts. Concentrations in water, sediment, and macroinvertebrate tissues were below harmful thresholds for all macroinvertebrate taxa found in the freshwater surveys. Exposure tests on amphipod species, Gammarus duebeni celticus and Gammarus pulex, revealed that microplastics did not inhibit their leaf shredding or predation roles at prevalent concentrations. Furthermore, these taxa show resilience to microplastics under deoxygenation, an aspect of anthropogenic pollution and climate change expected to rise and co-occur with the projected increase in microplastic pollution. However, species-specific differences in microplastic effect on Gammarus leaf shredding behaviour were observed at very high microplastic concentrations, contributing to the growing body of evidence that species-specific assessments for microplastic exposure are needed for accurate prediction of the impacts of this contaminant.

Conclusively, the current microplastic risk to NI's freshwater macroinvertebrates and their ecosystem functions is minimal. This offers NI authorities a unique opportunity to implement effective mitigate strategies, using this study's data, to prevent a substantial increase in microplastic pollution and maintain the health of our freshwater systems.

Date of Award	Dec 2023
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Department of Agriculture, Environment and Rural Affairs
Supervisor	Gary Hardiman (Supervisor) & Jaimie Thomas Allan Dick (Supervisor)