Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)


Virginia Institute of Marine Science


Emily B. Rivest

Committee Member

Jan McDowell

Committee Member

Donna Bilkovic

Committee Member

Sarah Karpanty


Climate change has caused gradual changes within marine environments within the last couple decades and is expected to continue to impact these ecosystems. Changes to these ecosystems are anticipated to emerge as adverse effects reach the lowest and highest levels within trophic food webs. For example, these environmental changes may change the abundance and distribution of species within their current geographic range. In extreme cases, climate change has already resulted in range shifts of terrestrial and marine species. A need for bioindicator species has emerged, so that they may be used to indicate when climate change may impact marine communities and whether these communities are at risk. Bioindicators are useful in that they can be early indicators for adverse effects and be used to indicate to decision-makers that intervention is needed before adverse effects can spread to the rest of a particular ecosystem. Bioindicators that are responsive to environmental changes are ideal for use. Mytilus edulis (blue mussels) and Donax variabilis (coquina clams) are two species that could potentially have use as bioindicators for climate change. However, it is not known how responsive the physiological condition of these species is to environmental changes. Our thesis objectives were to determine whether differences in the physiological condition and recruitment rate of blue mussels and coquina clams on the Eastern Shore are connected to seasonal water quality changes in the northern hemisphere Spring-Summer months and (2) to determine whether there have been long-term (9 years) changes in mussel and clam physiology and interpret these changes in the context of climate change. We found some evidence for a connection between blue mussel and coquina clam physiology and recruitment and seasonal changes in water quality on the Eastern Shore. We also found that blue mussel and coquina clam physiology did exhibit long-term spatiotemporal changes through time on Virginia’s Barrier Islands. Blue mussels showed an early indication of a possible range shift to come. On southern barrier islands, blue mussels either had lower physiological condition and recruit counts or had higher rates of decline in these metrics. Coquina clams on the other hand, only showed evidence of declines in their physiological condition at Hog Island. This could be an early sign of the sublethal impacts stemming from gradual environmental changes and may signal that blue mussels and coquina clams will continue to decline in quality and quantity in these areas of Virginia’s Eastern Shore. Declines in blue mussel quality and quantity could be worrisome as they not only provide several economic and ecological services that benefit humans, but also are an important food source for the migrating shorebird species that use Virginia Barrier Islands as a refueling station. While worrisome, this response in blue mussels does indicate that this species may be responsive to environmental changes. With additional targeted, experimental research, a framework could be established that uses blue mussel physiology to further indicate impacts of specific environmental conditions on Virginia’s Eastern Shore ecosystems.




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