Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item QUANTIFYING NITROGEN REMOVAL POTENTIAL OF BOTTOM CAGE (C. VIRGINICA) AQUACULTURE(2022) Shenoy, Stefenie; Harris, Lora A; Testa, Jeremy M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While management strategies for human-caused nutrient pollution have improved over the last decade, eutrophication and its ecological effects remain primary concerns in many coastal marine systems. In-water nutrient removal techniques are being explored for potential use as a management strategy, including oyster aquaculture operations. Where abundant, oysters have been shown to exhibit denitrifying potential beyond that which is assimilated into shell and tissue biomass. While nitrogen cycling dynamics are well studied and modeled on natural and restored reefs, equivalent processes within oyster aquaculture operations are less defined. This study adapts an existing mechanistic model of oyster filtration, biodeposition, and particle transport to capture the influence of an aquaculture farm on local sediment-water chemical fluxes. Modifications included (1) revising the spatial domain to represent an array of bottom cages, and (2) integrating an existing bioenergetics module to mechanistically couple simulated seston removal from the water column via filtration and subsequent biodeposition by simulating oyster growth. Model simulations included a variety of oyster densities, farm sizes, natural reef, and no oyster scenarios. Two seasonal sampling campaigns of a bottom cage aquaculture site provided model forcing and validation data. Model output revealed complex relationships among oyster density and distribution, farm size, oyster growth and biodeposition. The estimated rates of net nitrogen removal suggest increased potential for oyster aquaculture operations to receive credits above what is currently being realized, and the calculations of such removal for management purposes should consider lease-specific configurations and environmental parameters.Item BAHAMIAN OOLITIC ARAGONITE SAND IMPACT ON WATER QUALITY AND MITIGATION OF PHOSPHATE AND PHOSPHORUS REMOVAL AND RECOVERY IN RECIRCULATION AQUACULTURE SYSTEMS(2021) Rodgers, Steven R; Place, Allen R; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recirculating aquaculture systems (RAS) require management of water conditions to ensure animal health and limit nutrient discharges. Oolitic aragonite sand (OAS) forms from whiting events off the coast of the Bahamian Islands is a sustainable, renewable and effective in controlling water quality. Cyanobacteria mediate the precipitation of aragonite by capturing CO2, internally forming CO32-, which reacts with Ca2+ in seawater forming CaCO3 precipitations. Studies in freshwater, brackish and marine waters maintained stable pH and alkalinities. Initially, OAS removed phosphate rapidly, slowing afterwards. The OAS removed phosphate at rates of 716, 705 and 215 mg PO4/ kg OAS for freshwater, brackish and marine water, respectively. A system with daily P additions showed a removal capacity of 77.8 mg P /kg OAS. Treatment of phosphorus exposed OAS with 1.0% and 2.0% citric acid solutions show phosphate removals ranging from 17.3% to 93.5%. The citric acid increases the OAS surface area 1.66 times to 4.628 m2/g OAS, confirmed by SEM. Microbiome analysis show similar bacterial phyla exist on the naïve OAS and the OAS used in different salinities. Under anaerobic conditions, the control of system conditions were favorable for denitrification and anammox processes to occur. In freshwater, a loss of 215.8 gram of nitrogen (a loss of 90.5%) of the added nitrogen to the system occurred. In marine conditions, a loss of 253.04 g nitrogen, representing an 87.6% loss, occurred. Microbiome analysis identified phyla known to function as denitrifiers, though lacking known phyla for anammox bacteria. Losses of nitrogen in both salinities is likely due to denitrification, as oppose to anammox. OAS in RAS holding Eastern and Pacific oysters, showed dissimilar responses. The water quality remained in acceptable ranges for oyster growth. The survival in Eastern oysters (≥80%) contrasted with the Pacific oysters (≤56%). Weight increases occurred only with the Eastern oysters. Both species shows increases in shell length, width and height, but unchanged or decreases in weight. Reduced somatic growth and limited shell development occurred, perhaps due stresses from nitrogen spikes in the systems. OAS shows no positive advantage with oyster growth.Item Evaluating Substrate Rehabilitation Techniques for Bottom Culture of the Eastern Oyster (Crassostrea virginica) in Chesapeake Bay(2020) Long, Jessie Todd; Cornwell, Jeffrey C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The degradation of Chesapeake Bay bottom conditions and oyster beds over the past century from habitat destruction, overharvesting, disease, and sedimentation have resulted in many areas that are detrimental for healthy oyster populations. In leased oyster aquaculture areas, unsuitable bottom characteristics result in suboptimal survival. Although the addition of oyster shell as substrate has been a common practice for building new oyster beds, the current high cost and lack of available shell can make this approach impractical. The goal of this study was to measure the effects of new and traditional bottom rehabilitation techniques (harrowing and shell addition) on oyster survival and growth on three distinct bottom types. The data revealed that treatments, whether singularly or in combination, were insignificant in respect to oyster size and survival across all bottom types. However, the observed bottom type had a significant effect on the percentage of oyster survival.Item Development of Standardized Antimicrobial Susceptibility Testing Methods and Aeromonas salmonicida Epidemiologic Cutoff Values for Antimicrobial Agents Used in Aquaculture(2007-07-27) Miller, Ron Ashley; Kane, Andrew S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pharmacokinetics describes the time course of drug absorption, distribution, metabolism and excretion. Pharmacodynamics is the relationship between unbound drug concentration over time and the resulting antimicrobial effect. Pharmacokinetic/ pharmacodynamic (PK/PD) indices quantify the relationship between pharmacokinetic parameters (i.e., area under the concentration-time curve, AUC) and microbiological parameters (i.e., minimal inhibitory concentrations, MICs), and are used to establish interpretive criteria or clinical breakpoints. The three primary PK/PD indices used are the AUC over 24 h at steady-state/MIC (AUCss/MIC), the peak concentration/MIC (Cmax/MIC), and the percentage of time over 24 hours that the drug concentration exceeds the MIC at steady-state pharmacokinetic conditions (T>MIC). These indices can be used to determine both appropriate dosage regimens and index magnitudes required for efficacy and reduced antimicrobial resistance emergence. The goal of this work was to determine the relevant PK/PD index target (AUCss/MIC) for oxytetracycline (OTC) against Aeromonas salmonicida, causative agent of furunculosis in salmonids. To achieve this goal we first established a standardized MIC testing method for aquatic bacterial pathogens, then used this method to determine the in vitro susceptibility cutoff concentration (epidemiologic cutoff value) for OTC (and three other antimicrobial agents) against 217 A. salmonicida isolates. We conducted additional in vivo studies using rainbow trout to monitor achievable serum OTC concentrations in both healthy and A. salmonicida-challenged fish. We confirmed OTC to be highly efficacious against a susceptible A. salmonicida strain in vivo, and through pharmacokinetics studies, calculated the OTC AUCss in healthy and challenged fish to be 27.2 and 20.1 μg∙h/mL, respectively. The PK/PD index target reported in a neutropenic mouse model as the most applicable to the tetracyclines is an AUCss/MIC of ≥5. Either of the AUCss values divided by the current epidemiologic cutoff value for A. salmonicida isolates (1 μg/mL) yields a product greater than this AUCss/MIC target of ≥5. This work demonstrates PK/PD indices commonly used in studies in mammals to predict therapeutic efficacy can be applied in studies in fish.Item Evaluation of Off-Season Spawning Techniques and Larval Diet Supplementation of Yellow Perch (Perca flavescens)(2004-08-13) Rath, Mark Allen; Lazur, Andrew M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)400 yellow perch (Perca flavescens) were divided into four groups, each targeted to spawn in a different season. The photo-thermal conditions of each group were manipulated to mimic seasonal changes that initiate reproductive activity. Spawning occurred in all groups. Using photo-thermal manipulation it is possible to spawn yellow perch at different times of year providing multiple crops of fingerlings. Eggs and larvae of yellow perch were analyzed for fatty acid content. A feeding trial was conducted comparing experimental diets high in eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) to the traditional larval diet used by perch producers. Enriching live foods with EPA and DHA improved survival. Although it was high in both EPA and DHA, the emulsified diet used resulted in lower survival than the control diet because the larvae did not accept it. However, yellow perch larvae may be able to be weaned onto manufactured diets, further improving survival.