Kaley Major, Summer 2015 Update
During the summer of 2015, I focused on two different research projects:
First, I collaborated with the Christian laboratory in the Biology Department on their Tidmarsh Farm Restoration project. This research assesses the effectiveness of an active restoration effort on a disused cranberry bog. As a member of the Poynton laboratory, my involvement in the project has focused on answering several different questions by using field-collected and laboratory populations of the freshwater amphipod, Hyalella azteca. Hyalella is a common toxicology laboratory surrogate that is used to predict the effect of chemical contaminants on wild populations. Further, the results of toxicity tests performed with Hyalella are used in conjunction with toxicity tests on other organisms to establish water quality criteria at a regulatory level for the protection of aquatic life. Given Hyalella’s status as a model organism in toxicology and its presence at the Tidmarsh restoration site, our goals are to determine: 1) whether water quality changes that occur during and after the restoration cause toxicity to H. azteca compared to baseline before-restoration measurements, and 2) whether restoration activities cause a gene expression profile difference in wild H. azteca collected on site. For the preliminary assessment of water quality and gene expression, my collaborators and I collected site water and Hyalella for gene expression analysis from the pre-restoration Tidmarsh sites, a reference site, and an active cranberry farm site. Then, I exposed laboratory Hyalella to each different water collection in a 96-hour whole effluent toxicity test to monitor differences in survival. This first, pre-restoration time point test will serve as a baseline comparison for later active and post-restoration comparisons. While definitive results for this project will not be available for several years, this summer was a crucial first sampling time point in a series to help determine whether restoration efforts have a positive impact on ecosystem health.
The second research project I focused on this summer, involved the recent development of pesticide resistance in some populations of Hyalella. Several natural populations of H. azteca in California have recently demonstrated resistance classes of pesticides: the pyrethroids and the organophosphates. These pesticides are commonly used in agriculture, and the pyrethroids are still registered for use in landscaping and residential applications. While the mechanism of resistance in Hyalella has been determined in pyrethroid-resistant organisms, the frequency of mutated resistance alleles in these natural populations has remained largely undocumented. Allele frequency information in natural populations would give significant information regarding the impact that pyrethroids are having in natural aquatic ecosystems, and that information could be used to determine the risks of chronic environmental pyrethroid exposure in aquatic ecosystems. This summer, I worked to genotype organisms from populations that display pyrethroid resistance. Because the mechanism of organophosphate resistance in Hyalella has not been investigated, it is necessary to determine the mechanism of the resistance before being able to determine allele frequencies for resistance. To that end, I mentored a summer REU student who worked to sequence possible mutation sites in the organophosphate active site in some resistant populations with some success in discovering a candidate mutation. As this project progresses, I hope to be able to determine the major source of organophosphate resistance in select Hyalella populations and to establish allele frequencies for both pyrethroid and organophosphate resistance and wild type alleles in parallel. Such information will serve to give information about the nontarget impacts of extensive pesticide use in the United States on aquatic ecosystems.