Foodborne disease outbreaks associated with the protozoan parasite Cryptosporidium spp. are an emerging public health concern. Shellfish, including Eastern oysters (Crassostrea virginica) in Chesapeake Bay and other Atlantic coastal waters, have been identified as a potential source of Cryptosporidium parvum infection for humans. The inactivation of C. parvum and other pathogens in raw molluscan shellfish would provide increased food safety for normal and at-risk consumers. The objectives of this study were to evaluate the efficacy of three alternative food-processing treatments (e-beam irradiation, microwave energy, and high hydrostatic pressure processing) on the viability of C. parvum oocysts in Eastern oysters. Oysters were artificially infected with the Beltsville strain of C. parvum and subjected to the three treatments in separate experiments. The effects of the treatments were evaluated by inoculation of the processed oyster tissues using the neonatal mouse bioassay. E-beam radiation of in-shell and shucked oysters treated with doses of 1.0, 1.5 or 2.0 kGy produced significant reductions (P < 0.05) in C. parvum mouse infectivity. A dose of 2.0 kGy completely terminated the infectivity of C. parvum and did not adversely affect the visual appearance of the oysters. Microwave treatments of shucked oysters at time (temperature) exposures of 1 sec (43.2°C), 2 sec (54.0°C), and 3 sec (62.5°C) produced a reduction in C. parvum mouse infectivity of 26.7%, 33.3%, and 46.7%, respectively. Microwave treatments at 2 sec (54.0°C) and 3 sec (62.5°C) showed extensive changes in oyster meat texture and color. Thus due to lack of efficacy and unacceptable tissue changes, microwave treatment of oysters is not considered a viable food processing method. High pressure processing of shucked oysters at all pressures tested (305 MPa, 370 MPa, 400 MPa, 480 MPa, 550 MPa) significantly (P < 0.05) reduced infectivity of C. parvum oocysts as measured by the neonatal mouse bioassay. A treatment of 550 MPa at 180 sec produced the maximum decrease of C. parvum infectivity (93.3%). The results indicate that HPP (high pressure processing) can produce significant (P < 0.05) reductions in infectivity of C. parvum oocysts. Measurement of tristimulus color values of pressurized raw oysters at extended processing times from 120 sec to 360 sec at 550 MPa showed an increase (P < 0.05) in whiteness. One (e-beam irradiation) of the three food-processing treatments shows promise for commercial applications to reduce public health risks from cryptosporidiosis in Eastern oysters. / Ph. D.

The objective of this research was to determine if Vibrio populations, specifically V. vulnificus were affected in oysters by the processing methods employed in Virginia. This study was conducted between July and September in 1995 and during the month of August of 1996 when water temperature was expected to be high. Oysters were harvested from Virginia and the Gulf coast and shucked and blown by Virginia processors. They were tested for aerobic plate counts incubated at 35-37°C, salt content, pH, total Vibrios and V. vulnificus populations before and after processing. Oysters were stored in crushed ice and maintained an internal temperature of 1°C and tested at 5, 10, and 15 days after processing. Oysters were also stored at -9°C tested every one to two weeks. Procedures described in the Food and Drug Administration’s Bacteriological Analytical Manual for identification of V. vulnificus were followed. V. vulnificus populations were not significantly affected by blowing. V. vulnificus populations decreased in oysters stored at 1°C and -9°C. V. vulnificus levels decreased faster in blown oysters harvested from the Gulf coast. Vibrio populations were not significantly reduced by blowing in oysters that were 1°C. Oysters stored at -9°C showed decreased Vibrio populations. pH and APC showed an inverse relationship in oysters that were 1°C. In oysters stored at -9°C, pH and APC showed a positive correlation. Significance of these correlations varied. / Master of Science

Live eastern oyster (Crassostrea virginica) reefs have declined by 62.6% in Mosquito Lagoon (ML) along the eastern Florida coast since 1943. While this species creates reefs by successive generations of oysters recruiting to conspecific shells, C. virginica can also attach to non-reef substrates including mangrove roots and armoring (e.g., seawalls), which may help counteract reef habitat loss. In recent decades, warmer winters have enabled red (Rhizophora mangle) and black (Avicennia germinans) mangrove expansion in subtropical salt marshes and temperate estuaries where oyster reefs occur. Additionally, 11.8% of ML's shorelines have been armored as of 2018. These non-reef substrates add potential surface area and a 3-D substrate for oyster settlement. Aerial imagery from 1984 to 2021 was used to track extent (ha) changes in mangroves, oyster reefs, and hard armoring. Mangrove extent increased 859.2%, hard-armoring extent decreased 56.3%, and live oyster reef area decreased 55.3% (rate: -0.86 ha/yr). Additionally, 83 oyster reefs were 100% converted into mangrove islands, resulting in a 654.6% increase in the number of new conversions between 1984 and 2021. To determine if oyster abundances on non-reef substrates are comparable to live oyster reefs, oyster characteristics were compared between substrate types using field surveys to collect metrics (live densities, shell heights, canopy heights). Mean densities and canopy heights (± S.E.) were highest on concrete/metal seawalls (481.8 ± 113.0 oysters m2 and 678.4 ± 408.6 mm, respectively). Mean shell heights (± S.E.) were largest on oyster reefs (52.0 ± 2.2 mm) and within black mangrove pneumatophores on oyster reefs (41.3 ± 10.0 mm). Between 1984 and 2021, oyster reefs lost 291.0 oysters/ha versus non-reef habitats, which added an average (± S.E.) of 104.7 ± 78.2 oysters/ha. These findings suggest mangrove roots and armoring support oyster reef-level populations by providing 3-D attachment space and partially offset oyster losses on reefs.

Predation may be a key component of the unsuccessful restoration of the Eastern Oyster (Crassostrea virginica), a former keystone species in Chesapeake Bay. Here, I examine the polyclad flatworm Stylochus ellipticus and its potential role as an important predator of C. virginica. Using small-fragment size C. virginica specific DNA primers, oyster DNA was successfully detected in whole organisms homogenates of wild-caught S. ellipticus individuals. Of the 1,575 individuals tested, 68.1% tested positive, thus predation occurred. Predation did not appear to be affected by salinity or temperature; however, season did appear to have an effect on both predation and S. ellipticus abundance (p-value: <0.05). The findings also imply that S. ellipticus are highly mobile, entering the water column to reach hard substrate at various depths, whereas previous studies suggest otherwise. These findings are useful in the planning and management of oyster cultivation and restoration. Furthermore, this study outlines a method of diet study that may be more sensitive than traditional DNA-based techniques.

A simulation algorithm based on biological references points proposed by Powell and Klink (2007) is implemented for predicting the total allowable catch of eastern oysters (Crassostrea virginica) from Louisiana’s coast. The model accepts initial per-square-meter shell mass and oyster size distributions as input. Fishing effort is provided as fractions removed of each resource for each month of the season. The model outputs the expected remaining shell mass and harvests of sack and seed oysters after discrete fishing months. Oyster mortality credits the shell budget, while fishing fractions debit oyster and shell resources. Surviving oysters grow larger along a time-dependent von Bertalanffy growth curve. Fishing fractions are chosen heuristically with the goal of minimizing shell loss. Input data is collected by the Louisiana Department of Wildlife and Fisheries in their annual stock assessment. The model is available as a public web resource at www.oystersentinel.org.

<p>Curiosity is a powerful tool, and combined with the ability to observe the natural world, grants humankind an unique opportunity, the opportunity to wonder why. Why do things exist?, why do they do the things they do?, why is this even possible?</p> <p>Research in our lab is focused on the basic understanding and potential application of biological materials, in particular, biological adhesives produced by marine organisms such as oysters. Oysters produce a cement-like material that is able to withstand the dynamic conditions found in coastal environments. The focus of this dissertation is to lay the basis of the characterization of new biological materials by observing and analyzing its physical properties, to measure the performance of the material in natural conditions and finally to identify the basic components that give the material the properties that we observe. The end goal of this project is to understand the properties of this material so we are able to develop a synthetic system that is able to imitate, as close as possible, what we find in nature. These results, and more importantly, the new questions that emerge from this research, provide a first look at the adhesive system of oysters leading the way to new discoveries in the future.</p>

Salinity (S) and temperature (T) control every facet of the eastern oyster (Crassostrea virginica) life cycle, principally reproduction, development, growth, and mortality. Previous studies conducted in in the Breton Sound (BR) and Barataria (BA) estuaries have reported differences in growth and mortality rates between the basins. In the present study, environmental conditions were synchronized to compare growth and mortality rates between basins at similar combinations of T and S. Results indicate that when T and S are the same (synchronized), seasonal oyster growth and mortality rates differ between BR and BA. Seasonal analyses revealed that as salinities increased in both estuaries, growth rates generally increased, while mortality rates generally decreased. These findings suggest that basin-wide adaptations to local environmental conditions may exist.

Changes in freshwater inputs due to water diversions and increased urbanization may alter the function and properties of estuarine ecosystems in South Texas. Freshwater and nitrogen inputs from the Mission and Aransas rivers to the federally designated Mission-Aransas National Estuarine Research Reserve (Mission-Aransas NERR) have received considerable attention in the past few years. However, freshwater inputs from two rivers (the San Antonio and Guadalupe rivers) that combine and drain into a neighboring bay (San Antonio Bay) may also provide a substantial nitrogen source to Aransas Bay, which is within the boundaries of the Mission-Aransas NERR. In order to study the influence of the San Antonio and Guadalupe rivers, an oyster species, Crassostrea virginica, was chosen to provide time-integrated information about freshwater contribution as a nitrogen source within the bays. Chapter One addresses variations in isotope values ([delta]¹⁵N and [delta]¹³C) in oyster adductor muscle tissue from 2009-2011 along a sampling transect from the head of San Antonio Bay through Aransas Bay. Stable carbon isotope values increased linearly from approximately -25 % to -17 %, while stable nitrogen isotope values decreased from approximately +16 % to +10 % along this transect. The patterns in stable carbon and nitrogen isotope values are consistent with substantial mixing of river-supplied water and nitrogen from San Antonio Bay into Aransas Bay. Variations in nitrogen isotopic signature between periods of sustained drought and flood conditions were relatively small, suggesting that riverine nitrogen contributions were similar regardless of the amount of freshwater inflow observed during the time frame of this study. Chapter Two addresses the isotopic equilibration time for adult oyster adductor muscle tissue using a year-long transplant experiment (November 2010-November 2011). Full representation of ambient water isotopic composition in oyster adductor muscle tissues was determined to occur roughly a year after transplant. Oyster adductor muscle could therefore be useful for long-term monitoring of nitrogen contribution from freshwater sources, and would be valuable to include in concert with water sampling and analysis of other tissues that have shorter integration rates for a comprehensive view of an estuarine system. / text

Comparing the protein compositions of three fishes, grass carp exhibited lower band intensity at 47.9 KDa, β-tropomyosin (36.5 KDa), and missed the band at 15.9 KDa myosin light chain. Bigmouth buffalo had a darker tropomodulin (38.8 KDa) band and smaller α-tropomyosin (33-37 KDa) than silver and grass carp. The breaking force (611.8 g) and deformation (11.7 mm) of silver carp cooked gel were significantly higher than the other two fish products. The addition of starches at 2, 4, and 6% to the grass carp paste lowered the breaking force of the cooked gel in a dose-responsive manner compared to the control (P<0.05), but no differences were found in bigmouth buffalo. The bioumulated Murine Norovirus-1 (MNV-1) was found to maintain infectivity during storage of live oysters at 5°C for 15 days while the inoculated MNV-1 kept infectious for 20 days in cooked surimi and salmon fillet. Treatments with 4.0 kGy X-ray achieved the reductions of 3.7 log PFU mL-1 in pure culture or 2.7, 2.2, and 2.0 log PFU g-1 in half-shell oyster, salmon sushi and tuna salad, respectively. X-ray significantly reduced the population of internalized MNV-1 in live oysters from 4.3 ± 0.4 log PFU g-1 to 3.6 ± 0.5, 3.2 ± 0.2, 2.8 ± 0.2, and 2.5 ± 0.1 log PFU g-1, by 1.0, 2.0, 3.0, and 4.0 kGy X-ray, respectively. The population of MNV-1 was reduced to less than 2.0 log PFU g-1 at 5.0 kGy X-ray. The survivability of live oysters was not significantly affected by treatment with 5.0 kGy X-ray, in comparison with the control, for up to 10 days, respectively, during storage at 5°C. Fish sauce was fermented from the by-products of silver carp. The total nitrogen content of fish sauce made in April, and November were 9.86±0.9 and 9.71±4.5 g/l, respectively, which was significantly (p<0.05) higher than the sample of February (8.45±0.25 g/l ), reflecting seasonal effect. The total nitrogen, amino acid nitrogen, pH, and sodium chloride of fish sauce made from silver carp by-products met the international fish sauce standard code of CODEX STAN 302-2011.

Crassostrea virginica, the eastern oyster, is a native keystone species that inhabits many coastal and estuarine ecosystems along the Atlantic seaboard. Introduction of the eastern oyster into estuarine areas with limited current populations is gaining popularity as a pro-active approach to improve estuarine water quality. In November 2014 and April 2015, a total of five pilot oyster reef treatments were deployed in Brevard County: bagged adult oysters (grown by community members under their docks through oyster gardening) collected in fall 2014 and spring 2015, bagged clean shell, oyster restoration mats, and empty plots (control). Locations of deployment included a Merritt Island impoundment (Marsh Harbor), Nicol Park (Port St. John), and Scout Island (Melbourne Beach). Prior to deployment, we collected morphometric data (shell length, weight) on all gardened oysters. Abiotic factors including salinity, air and water temperature, and wind speed were collected monthly. During quarterly sampling at each site, morphometric data were collected for all live oysters, surviving and newly recruited. Results show survival of gardened oysters and natural recruitment differed by and depended greatly on the within-site location of each reef. In areas with no recruitment and limited gardened oyster survival, regular deployment of gardened oysters is needed for long term success. In areas with natural recruitment, bagged, clean shell or oyster restoration mats are most successful. Future restoration sites should be tested prior to any large-scale oyster deployments.