Interspecific competition and predation control euhaline oyster reef development Public Deposited

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  • March 21, 2019
Creator
  • Brodeur, Michelle
    • Affiliation: College of Arts and Sciences, Department of Marine Sciences
Abstract
  • Species interactions, including competition and predation, can drive the development of biogenic habitats across environmental stress gradients. Using the Eastern oyster (Crassostrea virginica) as a model, my dissertation investigates how competition and predation limit the distribution of euhaline oyster reefs to the intertidal zone. In the field (Chapter 1) I examined how competition with epibiota, which compete for space in the subtidal and low-intertidal zones, affects juvenile oyster growth and survival. I also tested if competition between oysters and epibiota diminishes with increasing oyster body size. Removing epibiota increased oyster survival, especially in the lower-tidal-exposure treatments where epibiota cover is high. Larger oyster body size resulted in significantly higher oyster growth than smaller body sizes at lower tidal exposures. Following competition with summer epibiotic communities, oysters are covered by macroalgae in the winter and spring. In Chapter 2, I quantified baseline macroalgal dynamics and explored the effects on oyster fitness. I found that macroalgal cover is controlled mainly by abiotic forcing and does not reduce oyster growth or survival. Predation may be another mechanism that causes oyster mortality the subtidal, but the settlement and predation rates may vary across different scales. I examined how oyster settlement and predation of oysters are affected by landscape setting, aerial exposure, and structural complexity (Chapter 3). Oyster settlement increased with inundation time and isolated reefs had greater settlement and adult densities than saltmarsh-fringing reefs. Oyster survivorship at low complexity was greater on isolated reefs than saltmarsh-fringing reefs and predation by nekton increased with increasing inundation. At high complexity, predation rates by mud crabs had highest at intermediate aerial exposures, likely due to an interaction of predator density and foraging behavior. Results from my dissertation indicate that predation and competition reduce juvenile oyster survival at low environmental stress, but net result of settlement and post-settlement processes is dependent on reef complexity and landscape setting. Restoring reefs on isolated sandflats immediately before oyster settlement in the lower-mid-intertidal will minimize competition with epibiota and predation.  Maximizing reef growth by reducing species interactions will increase reef complexity and further increase survivorship from predation.
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  • In Copyright
Advisor
  • Grabowski, Jonathan
  • Rosman, Johanna
  • Fodrie, F. Joel
  • Peterson, Charles
  • Piehler, Michael
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2016
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