Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Roger Mann


The objective of my research was to examine the physiology and behavior of metamorphosing oysters, Crassostrea virginica, and to investigate the effects of low oxygen stress on metamorphic processes. Specifically, I examined the effects of hypoxia (20% of air saturation) and microxia (&<&1% of air saturation) on settlement, survival, growth, morphology, metabolic rate and feeding on post-settlement oysters. All of the functions I measured were adversely affected by hypoxia and microxia, compared to normoxic controls. Survival times indicate that, like larvae and adults, post-settlement oysters are capable of anaerobic metabolism. The 2 week period following settlement is especially critical to recruitment. Low oxygen conditions increases mortality and have detrimental effects on the development and growth of post-settlement oysters. Oysters have the ability to feed at nearly all stages of settlement and metamorphosis. While hypoxic conditions reduce feeding only in the youngest metamorphosing oysters, microxic conditions affect all ages. Not only does weight-specific metabolism decrease as the oysters grow, but metabolic responses to low oxygen change from relatively oxygen independent to oxygen dependent. I conclude that oyster distribution may be influenced by low oxygen, especially in those areas that experience prolonged (24-48 h) hypoxia or severe microxic events. Low oxygen events may control recruitment into the adult population directly, because of larval settlement failure and post-settlement mortality, and indirectly, because of reduction in feeding, development rate, and growth of post-settlement oysters.



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