Title page for ETD etd-01122012-131516


Type of Document Master's Thesis
Author Eberline, Benjamin S
Author's Email Address bseberline@gmail.com
URN etd-01122012-131516
Title Population Dynamics of the Eastern Oyster in the Northern Gulf of Mexico
Degree Master of Science (M.S.)
Department Renewable Natural Resources
Advisory Committee
Advisor Name Title
La Peyre, Megan Committee Chair
Brown, Ken Committee Member
La Peyre, Jerome Committee Member
Keywords
  • mortality
  • breton sound
  • growth
  • gulf of mexico
  • oyster
  • disease
Date of Defense 2011-11-17
Availability unrestricted
Abstract
This project examined the economically and ecologically valuable eastern oyster (Crassostrea virginica) in the Northern Gulf of Mexico using field and laboratory experiments. Specifically, this project focused on natural rates of settlement, growth, and mortality in a variety of temperature and salinity regimes within Breton Sound, LA. Seed and market sized oysters in cages resting on the bottom, as well as settlement tiles, were monitored at four sites in Breton Sound, LA, along what is typically a salinity gradient ranging from ~5 to ~20. In April 2010, the Caernarvon Freshwater Diversion was fully opened with the goal of minimizing the impacts of the Deepwater Horizon oil spill on wetlands, resulting in extreme low salinity (< 2) at all sites through August 2010. High seed and market-sized mortality and reduced condition were observed in oysters at all sites. Perkinsus marinus infection prevalence in surviving market oysters was low at all sites and all infection intensities were light. Settlement only occurred at the highest salinity site. In May 2011, the Mississippi River flooded to record levels, resulting in low salinity (<10) at all sites through June 2011. This short period of low salinity minimized disease infection intensity and settlement at all sites. Oysters at the lowest salinity site experienced high mortality and low growth. Oysters at higher salinity sites experienced limited mortality, mostly from predation, along with higher growth and condition. While low salinity may be beneficial to oyster populations by reducing P. marinus infection levels, prolonged extreme low salinity through spring and summer appears to cause heavy mortality and negatively impact recruitment in the short term. While not only is it clear that the timing and duration of freshwater inputs will significantly affect the impacts on oyster resources, it is likely that large scale global climate patterns (including El Niņo and La Niņa events) will also modify how and to what extent freshwater events may affect Breton Sound. This project highlights the importance of understanding the timing and duration of low salinity events and their impacts on oyster life history stages.
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