Thesis (MAppSc) -- Auckland University of Technology, 2004. / Also held in print (104 leaves, ill., 30 cm.) in Wellesley Theses Collection. (T 639.41 PER)

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Appendices: leaves 136-141. Bibliography: leaves 119-135.

Thesis (Ph.D.)--University of Rhode Island, 2005. / Includes bibliographical references (leaves 168-188).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 94-99). Also available via the Internet.

Thesis (Ph.D.) -- Australian National University, 2007.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 135-148).

In recent years, mortalities of unknown aetiology have occurred in Pacific oyster aquaculture in Baynes Sound, BC during the summer. Field studies were conducted to examine environmental, reproductive and microbial factors that could be contributing to these mortalities. In 2017, oysters were observed at three sites from July 5 to September 15. Each intertidal site had three modules containing seven stacked trays with 80 oysters per tray. Final mortalities ranged from 9.3 ± 1.9 to 38.8 ± 4.9% per module. The mortality per module correlated significantly with gonad length and the proportion of oysters that were female in a multiple linear regression model (R2=0.824, p=0.002). Vibrio aestuarianus, a well-documented pathogen of farmed Pacific oysters in France, was well represented in bacterial cultures from intertidal oysters in 2017 based on recA gene sequencing of 158 bacterial isolates. In 2018, juvenile Pacific oysters were monitored to characterize the onset of a summer mortality event in suspended culture. From May 11 to September 17, data on shell size, reproductive development, environmental conditions, and the microbial community of gill tissue was tracked at culture densities of 150, 300, 450, and 600 oysters tray-1. The onset of mortality was associated with a period of rapid growth, reproductive development, and elevated temperatures. Cumulative mortality per tray ranged from 34 to 75%, with the highest density trays having significantly lower mortality (p=0.023), smaller shell width (p=0.001), smaller shell length (p=0.002) and smaller gonad length (p=0.049) than the lowest density trays in a linear mixed-effects regression. Histology of oysters from August 12, during the mortality event, showed a mixed microbial infection in peripheral gill tissue. High-throughput sequencing of the 16S rRNA gene and qPCR of V. aestuarianus using species-specific recA primers suggest V. aestuarianus is temporally associated with summer mortality. Mortalities observed in 2017 and 2018 occurred in different age classes and with different oyster culture techniques, but all were associated with elevated water temperature, increased reproductive effort, and the presence of V. aestuarianus. / Graduate / 2021-08-06

Of the many changes humans have caused in coastal systems, excess nutrient loading is perhaps the most dramatic. Specifically, excess nitrogen (N) can lead to a series of negative consequences such as eutrophication, low oxygen conditions, and decreased biodiversity. Concurrent with changes in nutrient loading, coastal shellfish populations have been devastated through overharvesting, disease, and pollution. For example, oyster reefs – once a dominant feature along many coastlines – have been reduced by 85% of their historic range globally. Today, oysters are returning to coastal systems through restoration projects and a boom in aquaculture. Yet the impact of returning oysters to coastal systems is unknown. My dissertation helps to fill this major knowledge gap. Specifically, this dissertation focuses on the role oysters play in regulating coastal nutrient cycling and greenhouse gas (GHG) emissions. In chapter one, I estimated the GHG cost of protein production using oyster aquaculture. Using a combined field and laboratory approach, I quantified rates of N2O, CH4, and CO2 release from cultured oysters, and changes in sediment fluxes of these GHGs. On a kg CO2-equivalent kg-1 protein produced, oyster aquaculture has less than 0.5% of the GHG cost of terrestrial livestock production. In chapter two, I took advantage of an oyster aquaculture chronosequence to examine how organic matter loading from oysters altered sediment N cycling processes over time. I found that sediment fluxes under oyster aquaculture oscillated over time, shifting between N removal (N2) and recycling (NH4+) processes, demonstrating non-linear dynamics. In chapter three, I demonstrate that sediment N cycling processes in oyster habitats follow seasonal patterns of water column productivity, recording net denitrification in the spring following a phytoplankton bloom and net nitrogen-fixation in the fall. In chapter four, I use a meta-analysis approach to describe the role of oysters in regulating coastal nutrient recycling, removal of excess N, and GHG footprint. I show that in a biogeochemical context oyster reefs and aquaculture are interchangeable habitat that stimulate both N removal and recycling, with only a small GHG footprint.

No description available.

Productivity, diversity and survival of estuaries are threatened by explosive coastal population growth and associated recreational activities. One major area of recreational growth has been the number of small pleasure craft motoring in shallow waters at high speeds. On the east coast of Central Florida in the Indian River Lagoon system, intense boating activity occurs year-round and intertidal reefs of the eastern oyster Crassostrea virginica with dead margins (piles of disarticulated shells) on their seaward edges are commonly found adjacent to major boating channels. The cause(s) of the dead margins is unclear. However, the disarticulated shells may be reducing reef sustainability if these surfaces are unavailable for larvae. Recruitment trials were run on eight reefs (4 with dead margins, 4 without) in three 8-week trials in 2001/2002. Significant differences were found for location on reef and season. For survival of recruits, significant differences were found for reef type, location on reef, and season. Sediment loads, percent silt/clay, and relative water motion were all found to be significantly higher on impacted reefs. Spring months were found to be the optimal time for larval recruitment to increase larval set and survival and to also decrease the effects of sedimentation and water motion. Based on these results, experimental restoration began May 2003 to develop an ecologically and economically feasible restoration protocol for this intertidal region. Four different densities of shells (0, 16, 25, 36) were attached to vexar mesh mats (45 X 45 cm) displaying shells perpendicular to the substrate. 360 mats were randomly deployed at one of six dentified optimum recruitment locations. Recruitment increased through June and was significantly higher on mats with 36 shells. This was followed by a large, expected decline in recruitment and survival in July/August, due to competition, predation and/or extreme high temperatures. Total live oysters on the restoration mats significantly increased during October 2003 through February 2003. These newly-created oyster reefs are moveable and provide optimal substrate and larval set to be transported post-recruitment to areas resource managers have slated for restoration to aid in reef sustainability. To determine the potential negative effects of flow and sediment levels on oyster larval settlement, which may be associated with an increase in boating actitivity, laboratory experiments were conducted. Eighteen trials, with competent oyster larvae, nine in flowing-water and nine in still-water were run at three sediment levels: no sediment, low sediment, and high sediment loads. Larval settlement was significantly higher in the still-water trials and both high and low sediment loads significantly reduced larval settlement.