Author ORCID Identifier:
Date of Graduation
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Biology (PhD)
Degree Level
Graduate
Department
Biological Sciences
Advisor/Mentor
Evans-White, Michelle
Committee Member
Magoulick, Daniel
Second Committee Member
Willson, John David
Third Committee Member
Entrekin, Sally
Keywords
Consumer Driven Nutrient Cycling; Ecological Stoichiometry; Elemental Phsyiology; Subsidy-Stress; Viralology
Abstract
Anthropogenic activities are reshaping the elemental composition of freshwater ecosystems, often creating stoichiometric imbalances that influence the growth, physiology and interactions of aquatic organisms. Ecological stoichiometric theory (EST) provides a framework for examining these changes by linking organismal elemental regulation to broader ecosystem processes. While traditionally focused on elements, such as carbon (C), nitrogen (N), and phosphorus (P), emerging stressors highlight the need to expand this framework to be more elementally inclusive for the examination of novel interactions. My dissertation integrates abiotic (salinization) and biotic stressors (viral infection) into an EST framework to evaluate how these factors alter elemental regulation at the organismal and ecosystem level. In controlled laboratory experiments, I first quantified how sodium chloride (NaCl) influences the homeostatic regulation of two taxonomically distinct algae. Dolichospermum, a cyanobacteria, exhibited non-homeostatic responses with increasing Na content but maintained stable C:N:P ratios and growth. Scenedesmus, a green alga, regulated Na uptake at low and high concentrations but exhibited sharper declines in growth and variable C:N:P. These contrasting responses suggest phylogenetically linked strategies in regulation of Na content. Building from the previous chapter I created a grazer-periphyton food web and manipulated NaCl concentrations and grazer identity [either presence of snails (Elimia) or crayfish (Faxonius)]. Grazer identity played a strong role in structuring periphyton assemblages and nutritional dynamics while salinization modified these effects. Halo-sensitive snails reduced grazing activity under salt stress, indirectly stimulating periphyton growth while excreting nutrients. Conversely, halo-tolerant crayfish maintained grazing pressure but both taxa exhibited elevated ammonium excretion in salinized treatments. These results indicate that grazer physiology and behavior interact with abiotic stressors to alter consumer driven nutrient cycling. Finally, I examined host-virus interactions in Sulfolobus islandicus, a hyperthermophilic archaea, with and without mobile genetic elements (MGEs). Viral infection diverted host resources towards viral proliferation, reducing host biomass accrual and the timing of the maximal biomass, altering dissolved nutrient pools. Plasmids modified the susceptibility of the host to viral infection and illustrate how MGEs can modify elemental fluxes in biotic and abiotic pools. Collectively, my dissertation demonstrates that salinization and viral infection alter freshwater elemental dynamics in distinct ways. By extending EST to include sodium and host-virus interactions my work advances a more elementally holistic framework for predicting how novel elements and stressors influence organismal performance, nutrient cycling, and ecosystem function.
Citation
Dias, S. A. (2025). Ecological Elemental Homeostasis and Stoichiometric Shifts: Biotic Responses to Ionic and Viral Stress. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6053
