Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
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
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Implications of Ocean Acidification for Three Pacific Arctic Bivalve Species(2016) Goethel, Christina Leigh; Grebmeier, Jacqueline M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sea ice retreat, seawater warming, and now ocean acidification are recognized as physical stressors impacting the productive benthic communities on the shallow continental shelves of the northern Bering and Chukchi Seas, particularly calcifying organisms like bivalves that are prey items for benthivorous predators including walruses, eiders, and bearded seals. Using time-series benthic faunal collections and laboratory experiments, my research: 1) evaluates the abundance and dominant size class of Macoma calcarea in the northern Bering Sea and the southeastern Chukchi Sea during summer months from 1998-2014, and 2) investigates the effects of ocean acidification on growth and oxygen consumption of two size classes of three dominant bivalve species, M. calcarea, Astarte montagui, and Astarte borealis. Results suggest a northward shift in bivalve distribution (p < 0.01) and a recent size reduction at both sites. Experimental results suggest that one dominant size class (2.1-3 cm) will be more susceptible to ocean acidification.Item CALORIC CONTENT OF BERING AND CHUKCHI SEA BENTHIC INVERTEBRATES(2012) Wilt, Lisa Marie; Grebmeier, Jacqueline M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Extensive seasonal sea ice reduction has highlighted the need to evaluate the status and potential long term changes of highly productive benthic communities in the Pacific Arctic Region. Walrus that use sea ice to access offshore feeding areas are now being forced to haul out on land for part of the year, requiring them to forage for benthic prey from closer to shore. To explore this energetic problem, I conducted a caloric survey of benthic invertebrates, and evaluated relationships between caloric content and environmental variables. Latitude was the strongest non-taxonomic dependency for caloric content (ANOVA p=0.003 with taxon dependencies, p<0.001 without). Cluster analysis revealed caloric densities were higher in offshore, high nutrient Bering Sea Anadyr Water, and lower in nearshore, low nutrient Alaska Coastal Water. An evaluation of preservation techniques indicated formalin fixation increased infaunal caloric content (p<0.001), suggesting caution while converting traditional benthic population studies to caloric values.Item IDENTIFYING AND TRACKING MARINE PROTEIN AND ITS IMPORTANCE IN THE NITROGEN CYCLE USING PROTEOMICS(2011) Moore, Eli Kelly; Harvey, H. Rodger; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Protein comprises the largest compartment of organic nitrogen in the ocean, and makes up a major portion of organic carbon in phytoplankton. Protein has long been thought to be highly labile in the environment and rapidly lost during diagenesis. However, the analysis of dissolved and particulate organic matter with NMR has revealed that much of dissolved and particulate marine organic nitrogen is linked by amide bonds, the very bonds that join amino acids in proteins. Throughout the global ocean, total hydrolysable amino acids (THAAs, the building blocks of proteins) can be measured in the water column and sediments, yet their biosynthetic source has remained elusive. Here, analytical techniques were developed combining protein solubilizing buffer extractions, gel electrophoresis, and proteomic mass spectrometry in order to investigate the biogeochemical significance of marine protein from primary production during transport and incorporation in sediments. These techniques enabled the detection and classification of previously unidentified marine sedimentary proteins. Specific proteins were tracked through the water column to continental shelf and deeper basin (3490 m) sediments of the Bering Sea, one of the world's most productive ecosystems. Diatoms were observed to be the principal source of identifiable protein in sediments. In situ shipboard phytoplankton degradation experiments were conducted to follow protein degradation, and it was observed that individual proteins remained identifiable even after 53 days of microbial recycling. These studies show that proteins can be identified from complex environmental matrices, and the methods developed here can be applied to investigate and identify proteins in degraded organic matter from a broad range of sources. The longevity of some fraction of algal proteins indicates that carbon and nitrogen sources can be tracked down the marine water column to sediments in diatom dominated systems as well as other types of phytoplankton. Using proteomic techniques to understand the marine carbon and nitrogen cycles will become increasingly important as climate change influences the timing, location, and phylogeny of those organisms responsible for oceanic primary production.