Predicting the impacts of anthropogenic stress on aquatic populations: a case study in resource-consumer-toxicant dynamics
Loading...
Links to Files
Permanent Link
Author/Creator
Author/Creator ORCID
Date
2018-03-14
Type of Work
Department
Program
Towson University. Environmental Science and Studies Program
Citation of Original Publication
Rights
Subjects
Abstract
The overarching theme of this research was bridging the gap between individual- and population-level effects of anthropogenic stressors under the current paradigm of ecological risk assessment. There is a general dissonance in scales of biological organization and energetic complexity between ecotoxicological studies and the natural environments in need of protection. Traditional toxicity tests assess stressor effects on individuals, while protection goals are generally concerned with the population level and above. Additionally, these tests largely ignore the impacts that the resource environment and the physiological state of a given individual have on toxicological outcomes. As such, the main objective of this research was to explore effects of – and interactions between – resource availability, individual physiology, and stress response at the individual and population levels using Daphnia magna as a model aquatic organism. The research began with an exploration of how manipulations to quantitative and qualitative aspects of the resource environment altered the physiology and stress response of laboratory D. magna. Among the scenarios tested, per capita food level driven by intraspecific competition in density-stressed populations was deemed the most influential on D. magna stress response. Thus, the next study assessed the outcomes of pulse toxicity of the fungicide pyraclostrobin to D. magna populations, with the hypothesis that density-dependent changes in food level per capita at various phases of population growth would result in different population stress responses. Differences in population mortality and recovery were observed at each of four population growth phases. A multi-age acute toxicity study, determining the 48h LC50 for D. magna and pyraclostrobin at three age classes and two food levels, suggested that pyraclostrobin toxicity was food- and size-dependent. Lastly, food- and size-dependent toxicity were incorporated into a bioenergetic modelling framework (DEB-IBM) as an exercise in refining model output of population-level impacts of anthropogenic stressors. In summary, the results of this research demonstrate the importance of considering the resource environment and physiology of individuals when attempting to predict the impacts of anthropogenic stressors on natural populations. While traditional toxicity tests generate general toxicity benchmarks, the use of more ‘non-traditional’ methods may greatly improve the informative capacity of experiments and the predictive capabilities of energetic models. And as the goal of ecological risk assessment is to protect populations, communities, and ecosystems from anthropogenic stressors, it is important that our methods first be able to robustly bridge the gap between individual- and population-level effects