Plastics and the Hidden Majority: Conservation Implications for a Threatened UK Freshwater Fish

Humanity is currently operating outside the planetary boundary for novel entities, with plastic pollution emerging as a significant concern. Global plastic mass, including current use and plastic waste, is estimated at double the mass of all living animal biomass. River sediments can accumulate microplastic contamination, with particularly high contamination in urban hydrometric areas. Higher loadings of microplastic contamination have been observed in sediments compared to the water column and areas with both depositional habitats and low water velocity. Lamprey larvae burrow in depositional freshwater sediments for up to seven years and feed on deposited organic matter. Despite this overlap, the extent of microplastic contamination in lamprey larvae, to the best of my knowledge, has not been documented. Few would say that lamprey species are charismatic, it’s parasitic life stages, unusual image and contrasting management views globally result in these species falling low on the priority list. However, this important ecosystem engineer, protected across Europe is one which this thesis aims to bring front and centre. Considerable knowledge gaps present both research opportunities and challenges. To date management and research efforts have focused on the upstream migration of adult lamprey, due to the threats from anthropogenic barriers. Certainly, an important factor in the conservation of lamprey across Europe, however there is a lack of research into other emerging threats to this primitive species. This thesis has filled in knowledge gaps concerning the exposure of lamprey larvae to microplastic contamination and the ecotoxicological effects associated with such exposure. The research develops novel methods to optimise the isolation of microplastic particles from complex organic tissue, microplastics identification and automated data analysis. The findings suggest that microplastic contamination is present in wild lamprey populations from Scottish rivers, with different age classes of larvae ingesting distinctive polymer types. To understand whether exposure to microplastics leads to identifiable effects in lamprey, behavioural and developmental end points were considered in experimental systems. These studies suggest microplastic exposure elicits impacts on larvae behaviour and early development. The results obtained from can be used to support further research and to aid development of future studies aimed at conservation management of this ecologically important species.