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Full-Text Articles in Physical Sciences and Mathematics
The Effects Of Hypoxia And Freshwater Intrusion On The Eastern Oyster (Crassostrea Virginica), James Henry Gledhill
The Effects Of Hypoxia And Freshwater Intrusion On The Eastern Oyster (Crassostrea Virginica), James Henry Gledhill
Electronic Theses and Dissertations
Recent estimates revealed a significant decrease in oyster populations worldwide. This drastic decrease has detrimental effects on coastal and estuarine ecosystems. Two environmental stressors that are thought to be contributing to the oyster population decline are hypoxia and excess freshwater intrusion. In this study, effects of hypoxia and low salinity on oysters were investigated using a combination of laboratory and field-based methods. In the laboratory, oysters were exposed to 2, 4, or 8 days of hypoxia (< 2 mg/L dissolved oxygen) folloby 6 days of recovery in normoxic conditions. At the same time, caged oysters were exposed to a naturally occurring hypoxic event in the field. After 8 days, laboratory-exposed oysters shoevidence of immunosuppression indicated by significant downregulation of the immune-related gene thymosin-β4 (Tβ-4) and a significant decrease in total circulating hemocytes compared to controls. However, in field oysters exposed to a naturally occurring hypoxic event, no effect on total hemocyte counts and an upregulation of Tβ-4 was observed. In a second field study, to investigate how oysters respond to prolonged freshwater exposure, caged oysters were placed on 23 April 2019 at six reef sites in the Mississippi Sound along with in situ water quality sensors. One-hundred percent mortality of caged oysters occurred at four of the six sites. Of the 6 six sites, Henderson Point Reef and Kittiwake Reef shosome caged oyster survival. At Henderson Point, where higher mortality was observed compared to Kittiwake, a significant increase in lipid peroxidation was detected. Analysis of mRNA expression of surviving caged and native oysters revealed downregulation of genes involved in immune function, low oxygen response, and osmoregulation. These results show possible evidence of energetic depression which inhibits adequate adaptation to low salinity conditions. Energetic depression and increased oxidative damage could have contributed to higher oyster mortality. Dredge sampling of native oysters at the all Mississippi Sound field sites on 27 September 2019, following recovery to ~15 ppt salinity, still indicated 100% native oyster mortality due to the prior prolonged freshwater exposure. Continued monitoring of western Mississippi Sound oyster reefs is crucial to observe recovery of oyster populations.
Effects Of Halogen Bonding And Nir Tuning Of Dyes For Dye-Sensitized Solar Cells, Alexandra Baumann
Effects Of Halogen Bonding And Nir Tuning Of Dyes For Dye-Sensitized Solar Cells, Alexandra Baumann
Electronic Theses and Dissertations
With current energy demands being met through the utilization of energy sources such as petroleum, natural gas, and coal, the non-renewable nature of these sources will eventually approach depletion as world wide energy consumption increases yearly. As a result the need for a renewable energy alternative has become imminent. One appealing alternative that has gained considerable attention since its development due to a low cost and a high solar to electric conversion efficiency are dye-sensitized solar cells (DSCs). This dissertation describes efforts to design and synthesize improved organic dyes utilizing three analogous methods: first, through decreasing non-productive pathways such as …