Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item MECHANISMS OF SORPTION OF PHARMACEUTICAL AND PERSONAL CARE PRODUCTS TO MICROPLASTICS(2021) Sanchez, Alterra; Gonsior, Michael; Yonkos, Lance; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Microplastics (MPs) are found in almost every ecosystem and in many commercially important seafood species. MPs have been found to be physically harmful to marine organisms, but also may act as vectors for organic pollutants and together have been shown to cause toxic effects in a variety of species. Wastewater effluent is a significant source of MPs to aquatic systems, as well as pharmaceutical and personal care product compounds (PPCPs). The first research contribution was to create a reference material for secondary fragment type microplastics of the polymer’s high-density polyethylene (HDPE) and polypropylene (PP) that is standardized by surface area (SA) for use in sorption and toxicity studies. Standardization for both polymers was successful, with a SA coefficient of variation of ~3%. PP MPs had greater SA due to it being a less crystalline polymer than HDPE. This reference material may act as a more realistic material than purchased powders or beads, as well as provide a more readily comparable material for fragment type MPs. The second research contribution used the reference material to create an extraction methodology for measuring semi-polar PPCPs associated with MPs. Acetone was chosen as the best solvent for extraction and extraction efficiency for both polymers was ~88% (first extraction). This methodology was then used to measure the equilibrium of the antimicrobial triclocarban with PP and PE of different MP particle sizes. Smaller particles with greater SA sorbed more triclocarban, rather than larger particles. PP had greater sorption of triclocarban than PE. This was due to PP MPs having greater SA due to being a less crystalline polymer. The third contribution created a framework for prioritizing study compounds based on environmental relevance for MP sorption using polyethylene as a model polymer, water solubility, and a correlation with the octanol water-distribution ratio, DOW, rather than the octanol-water partition coefficient, KOW. A possible threshold for polyethylene sorption was found for compounds with water solubility ~20-60mg/L and DOW ~3.7. This dissertation advances the understanding of MP reference materials, extraction methodology, sorption mechanisms, and modeling of sorption data of PPCPs.Item THE BEHAVIOR OF THE SCYPHOMEDUSAE CHRYSAORA QUINQUECIRRHA AND AURELIA AURITA AND ITS ECOLOGICAL IMPORTANCE(2004-11-23) Matanoski, Joseph Carroll; Hood, Raleigh R; Purcell, Jennifer E; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Scyphomedusae are important components in trophic and community structures of marine and estuarine systems worldwide. Behavior likely has a significant influence on medusa population dynamics and growing evidence points to the disproportionate effect individual behavior has on population responses, yet there are few quantitative studies of medusa behavior and no method for quantifying the behavior of individual pelagic organisms. A numerical model of medusa swimming behavior would be an important tool for assessing its effect on spatial patterns and foraging efficiency. An approach was developed that uses a suite of statistical techniques to quantitatively describe time-dependent changes in behavior of pelagic organisms and tested on the swimming behavior of Aurelia aurita and the foraging behavior of Chrysaora quinquecirrha. An individual-based model of medusa swimming behavior was formulated as a correlated random walk of velocity vectors in three dimensions. Each A. aurita medusa exhibited a unique swimming behavior, including varying swimming bell pulsations, speed, and turning at characteristic frequencies. C. quinquecirrha swam in mostly linear trajectories that alternated between periods of slow and fast swimming while searching for prey, but swam at a constant moderate rate with increased anisotropic turning while feeding. Foraging behavior by medusa groups depended on interindividual and intraindividual variability in medusa behavior, including deterministic changes in swimming pulsation strength and turning. Empirical and model results showed that variability of behavior among medusae and by individual medusae over time are integral components determining the aggregated population response. Medusa foraging behavior appears adapted for patchily distributed prey. Alternating between slow and fast swimming while searching for prey may minimize energy expended while periodically generating prey-entraining currents. Increased turning in the presence of prey increases the likelihood of remaining in prey patches. Anisotropic turning created vertically spiraling paths, well suited to horizontally compressed prey patches. Model results demonstrated that medusae tend to swim toward and accumulate at the surface, avoid direct contact with the bottom, orient search patterns to long-range stimuli (e.g. gravity) and feeding patterns to local stimuli (e.g. prey contact), and exhibit periodicities of velocity outside prey patches and turning within patches that result from deterministic behavior.