Thesis (Ph. D.)--University of Wisconsin--Madsion, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 281-304).

Dusky kob, Argyrosomus japonicus, is an aquaculture species in South Africa that is in pilot commercial production. While the major nutrient requirements of the species are known, the advantages of incorporating formulated feeds into the diet of the species has yet to be fully explored. Research on formulated feed composition is required to: minimise input costs; improve the organoleptic properties and meat quality; and minimise nutrient loss, which contributes to environmental pollution. This study sought to test the impact of different lipid levels in aquafeeds fed to dusky kob juveniles by determining: (i) growth performance, feeding efficiency, proximate and fatty acid composition; (ii) chemical changes and shelf-life of refrigerated fish fillets; and (iii) metabolic rates and nitrogen excretion of juvenile dusky kob. And more...

Includes bibliographical references. / Identifying the chemical compounds that attract urchins to seaweeds will increase sea urchin aquaculture efficiency as these compounds can be utilized in the production of artificial feeds enhancing their attractiveness and palatability. This study investigated the chemosensory preferences of the tropical sea urchin Tripneustes gratilla for four crude extracts of Ulva as well as Fresh Ulva and an artificial feed. The four crude extracts of Ulva (Methanolic, Ethanolic, Chloroform and Chloroform-Methanol extracts) were tested by pair-wise chemosensory trials in a Y shaped maze. Urchins were significantly deterred by both the Chloroform and Chloroform- Methanol extracts as well as the solvent controls and artificial feed, however T. gratilla was significantly attracted to both the Methanolic and Ethanolic extracts. These two extracts were tested individually against Ulva and the urchins could not distinguish between Ulva and the extracts. When these two extracts were tested against one another it was found that the urchins were significantly attracted to the Methanolic extract. The Methanolic extract was then added to the artificial feed and significantly improved the feeds attractability. This indicates that these extracts, or the compounds which are responsible for this effect, can be incorporated into artificial feeds thereby making them more attractive to the sea urchin. The percentage yield of Ulva that each solvent extracted was different, although only the Ethanolic extract was found to be significantly different from the Chloroform and Chloroform-Methanol extracts. Future studies are needed to examine the chemical composition of these specific chemosensory compounds. By incorporating these attractive extracts into artificial feeds, South Africa can potentially improve the cultivation success of T. gratilla therefore expanding the economy of the local aquaculture industry through the export of this highly valued seafood product.

Rivers deliver approximately 260 Tg of dissolved organic carbon (DOC) to the ocean annually, yet there is little evidence of terrigenous DOC (tDOC) in the ocean. While tDOC was historically believed to be stable and resistant to microbial degradation, it has recently been shown that freshwater systems mineralize more tDOC than originally thought. Biodegradability of DOC is an overriding control on ecosystem respiration, regulating how much organic carbon is remineralized as CO2 or exported downstream, however, the processes controlling DOC degradation are not well understood. The priming effect is a possible mechanism by which inputs of biolabile DOC enhance the bioavailability of stable DOC components in aquatic systems, resulting in higher rates of microbial remineralization. Here we investigate microbial degradation of DOC by conducting bioincubation experiments and assessing a variety of biogeochemical controls on DOC biolability, including the priming effect, nutrient availability, seasonality, and chemical composition. The role of priming and nutrient availability was assessed through the inclusion of bioincubation treatments amended with nutrients and a variety of simple biolabile organic carbon substrates. Ultrahigh resolution mass spectrometry allowed us to characterize the molecular composition of dissolved organic matter (DOM) samples and understand how chemical composition may act as a driver of DOM biodegradability. This study was first conducted on blackwater systems in Florida, where we collected blackwater river samples and made leachates from plant litter that largely contributes to the terrestrial input of organic matter in these systems. Blackwaters consist of a diverse mixture of organic substances and are ideal study sites for assessing biodegradability of DOC and priming as they are rich in organic matter (i.e. high DOC concentrations), dominated by DOM that is highly aromatic in nature, and are historically believed to be a stable DOM pool. During the bioincubation experiments, blackwaters lost 6.10 ± 3.85% DOC within one month, while leachates lost 38.10 ± 16.74% DOC. There were no significant differences between DOC remineralization in control and ‘primed’ treatments, indicating that priming is not an important factor in the biodegradation of DOC in blackwater ecosystems. However, the proportion of biodegradable DOC (BDOC) and DOM composition were significantly correlated, mostly driven by the contribution of aliphatic compounds (H/C ≥ 1.5, O/C < 0.9) that were abundant (9.3 ± 5.2%) in leachate DOM. The molecular signature of biodegraded leachate DOM resembled that of stable blackwater DOM, indicating that bioavailable DOM components leached from plant litter are rapidly utilized and stable DOM is exported downstream. Further, we conducted this study on permafrost-influenced streams in the Yukon Flats of Interior Alaska, a region underlain by discontinuous permafrost that is experiencing rapidly warming temperatures, permafrost thaw, and associated changes in hydrology and vegetation, all which affect the biodegradability and fate of DOC. Permafrost-influenced streams may also be sites of ‘priming effects’ as biolabile, ancient permafrost DOC mixes with relatively modern, stable stream DOC. To determine the vulnerability of DOC in this region to microbial degradation, we conducted 28-day bioincubation experiments utilizing a suite of stream samples and leachates made from fresh ground vegetation and several soil layers collected at different depths, including permafrost. Microbial utilization of stream DOC ranged from 4 to 11% in spring and differences were likely influenced by site drainage characteristics. Leachate DOC followed a continuum of biodegradability, losing from 9% (mineral soil-derived) to as much as 66% (vegetation-derived) DOC. Nutrient availability rather than priming controlled DOC remineralization, especially for fall stream samples and mineral soil leachates. Seasonally, it appears that DOC biodegradability and aromaticity decrease into fall. The molecular composition of DOM determined by ultra-high resolution mass spectrometry was significantly correlated to DOC biodegradability, particularly the contribution of aliphatic compounds. Stream microbial communities utilized 50-56% of aliphatic compounds in permafrost-derived DOM within 28 days. We also found evidence for selective preservation of aromatic DOM compounds with depth in soil horizons. Our findings imply that future climate-driven changes (e.g. temperature, nutrient supply, and vegetation) in discontinuous permafrost regions may cause the release of biolabile DOM that is rapidly respired, resulting in a positive feedback with climate change. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / June 29, 2018. / biodegradability, dissolved organic carbon, dissolved organic matter, leachates, priming / Includes bibliographical references. / Robert Spencer, Professor Directing Thesis; Jeffrey Chanton, Committee Member; Olivia Mason, Committee Member.

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen viewed (2/6/2008). Includes bibliographical references (p. 47-50).

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Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 198-211). Also available online in ProQuest, free to University of Oregon users.

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