Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item USING CALCEIN, A FLUOROCHROME CHEMICAL TAG, TO MARK SHELLS OF THE EASTERN OYSTER, CRASSOSTREA VIRGINICA, AND TO VALIDATE DIRECT SETTING OF OYSTER LARVAE(2021) Spires, Jason Eugene; North, Elizabeth W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Effective management of fisheries necessitates the advent and use of tools to monitor wild and introduced species. Tools currently available for marking shells of eastern oysters (Crassostrea virginica) predominantly rely on the physical handling of individual organisms and do not lend themselves to labeling large numbers of individuals with a durable tag. To test and apply an effective mass-marking tool for C. virginica, this research focused on 1) determining the efficacy of chemical labeling of multiple life stages of C. virginica using calcein, a fluorochrome dye, and assessing the potential impacts on survival and growth, and 2) identifying if the larval marking method could be used to validate the direct setting method of oyster stock supplementation that involved releasing larvae onto suitable habitat in situ. To investigate objective 1, multiple life stages of C. virginica were exposed to calcein immersion baths and tracked over time in laboratory experiments. Objective 2 was investigated through an applied field experiment that released calcein-tagged larvae onto constructed artificial reefs that were recovered and assessed for the presence of tagged juveniles. Results from labeling all life stages indicate that C. virginica readily incorporate calcein into shells with minor effects on settlement, growth, and survivorship at concentrations of 25 and 50 mg l-1 for larvae and 250 mg l-1 for juveniles and adults. These marks could be seen without sacrificing individuals, were visible on the shells of juveniles for at least four years, and were retained on the shells of pediveliger larvae for four weeks post metamorphosis. Calcein had little to no effect on the survival of most juveniles and adults and had no effect on the settlement rates of larvae. Field deployments of marked larvae on artificial reefs in the Tred Avon River showed that marked larvae were recovered in high concentrations at release sites, indicating that ‘direct setting’ of pediveligers onto shell bags in situ is possible without enclosures. This is the first known successful test of direct setting of C. virginica pediveliger larvae in situ that was verified with chemical mark and recapture methods. These findings have wide application for supporting C. virginica research, restoration efforts, and industries: these techniques could be used to strengthen comparative growth studies, validate larval transport models, evaluate stock enhancement activities, support law enforcement efforts, and enable testing of alternative setting strategies.Item THE EXCHANGE OF EASTERN OYSTER (CRASSOSTREA VIRGINICA) LARVAE BETWEEN SUBPOPULATIONS IN THE CHOPTANK AND LITTLE CHOPTANK RIVERS: MODEL SIMULATIONS, THE INFLUENCE OF SALINITY, AND IMPLICATIONS FOR RESTORATION(2015) Spires, Jason Eugene; North, Elizabeth; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With limited funds available for restoration and management, information is needed that would enhance the objectives of restoration of the eastern oyster (Crassostrea virginica) in Chesapeake Bay. One challenge with choosing locations for C. virginica restoration is lack of information regarding larval exchange, which helps determine whether the reefs will be self-sustaining and/or enhance nearby populations. The goal of this research was to estimate the larval exchange between subpopulations within the Choptank and Little Choptank Rivers (Maryland, USA) and to determine the influence of low salinity on these patterns in connectivity. To this end, the Lagrangian TRANSport model (LTRANS) was coupled with a Regional Ocean Modeling System hydrodynamic model of Choptank River (ChopROMS) and applied to predict the exchange of simulated C. virginica larvae between 596 reefs within the system. Model results indicated that there is a high degree of connectivity among the subpopulations in this system. Most simulated larvae were transported down river (rather than upriver). Reefs in upper portions of the Choptank River and its tributaries were in a position to produce the most larvae which encountered suitable habitat, whereas those in the lower Choptank River received the most simulated larvae. In addition, salinity-induced mortality of larvae substantially decreased transport success and self-recruitment, and changed patterns in reef-specific transport success throughout the estuary. Model results provide region-specific information that could be used to support restoration efforts in areas with low salinities like the Choptank River.