AQUASTRESS:Non-additive impacts of climate change and anthropogenic stressors on host-symbiont dynamics

Jones, Alice 2025. AQUASTRESS:Non-additive impacts of climate change and anthropogenic stressors on host-symbiont dynamics. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Freshwater ecosystems are among the most ecologically diverse yet increasingly vulnerable environments on the planet, threatened by a growing array of interacting anthropogenic stressors. These pressures not only impact species persistence but also disrupt the ecological relationships between hosts, parasites, and symbionts that underpin community structure and ecosystem function. This thesis investigates how multiple stressors including temperature, chemical pollutants (glyphosate, nitrate, acidification, rotenone) and microplastics, individually and interactively affect freshwater symbiotic associations across molecular, experimental, and conservation contexts. Firstly, a phylogeographic foundation was provided by resolving the identity and global structure of Chaetogaster limnaei limnaei, revealing substantial cryptic diversity but limited host specificity. Chapters 3 to 5 apply a multi-stressor ecotoxicological lens, demonstrating that warming interacts with chemical pollutants in complex, non-additive ways to affect symbiont survival and reproduction. These interactions often defied predictions, with reversal, antagonistic and synergistic effects on the symbionts and hosts. Chapter 6 expands this framework to a host–pathogen model system, showing that Roundup and microplastic exposure altered parasite burdens and survival outcomes in opposing directions, exposing trade-offs in host resilience. Finally, Chapter 7 documents the coextinction of a specialised parasite assemblage following the loss of a benthic Arctic charr morph, highlighting the broader biodiversity costs of ecosystem interventions. Collectively, this work reveals the sensitivity of freshwater symbioses to compounded environmental stress, demonstrating that shifts in species interactions, not just in species alone, are critical in understanding and predicting ecosystem responses under global change. These findings underscore the need for conservation frameworks that recognise the functional roles of parasites and symbionts in maintaining aquatic biodiversity and ecosystem resilience.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	5 May 2026
Last Modified:	06 May 2026 09:20
URI:	https://orca.cardiff.ac.uk/id/eprint/186775

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