The effects of microplastics on freshwater populations, communities, and ecosystem functioning: Integrating multiple human-induced pressures
Year: 2024
Type: article
Abstract: Microplastics are an emerging contaminant of high concern due to their physical and chemical properties that can cause harm to aquatic organisms, their populations, communities, and ecosystems. In this thesis, I explored the combined effects of microplastics and other anthropogenic pressures, including nutrient load and environmental warming, on freshwater communities and ecosystem functioning. In Chapter 2, I conducted a quantitative review of the literature assessing the interactions between microplastics and chemicals, to determine whether microplastics act as a vector for the introduction of harmful chemicals to aquatic biota. Unexpectedly, I show that hydrophobicity (as log KOW) and microplastic particle size do not strongly affect the interaction between microplastics and chemicals in marine and freshwater environments. From the literature to date, there is no evidence to suggest that microplastics enhance the toxicity of environmental chemicals to marine or freshwater biota. In Chapter 3, I worked on a large-scale mesocosm experiment to determine the effects of different microplastic types and concentrations, in combination with nutrient enrichment, on freshwater planktonic communities and ecosystem functioning. I found that taxonomic richness and community composition were not affect by exposure to the experimental treatments, and that there were no significant treatment effects on phytoplankton standing stock, periphyton productivity, total or microbial leaf litter decomposition. In Chapter 4, I looked at sub-lethal responses of benthic shredders to determine whether microplastic pollution could have negative implications for species interactions. As expected, the respiration rates of Gammarus pulex increased, but there were no effects of microplastics alone, or in combination with experimental warming, on the respiration rates, feeding rates, or movement speeds of either G. pulex or A. aquaticus. Overall, this thesis provides an ecologically relevant assessment of microplastics and their effects on freshwater organisms, populations, communities, and ecosystem functioning. This work highlights the importance of considering other ecologically relevant parameters and sub-lethal responses when generating a risk assessment for microplastics in the environment.
Author: Marchant, D
Language: English
Subfield: Pollution
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7009294307