Date of Award

Spring 5-13-2017

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Paul Rawson

Second Committee Member

Sara Lindsay

Third Committee Member

Malcolm Shick

Additional Committee Members

Rebecca Van Beneden

Nikki Adams (California Polytechnic State University)

Abstract

In this study, we compared the osmotic stress response of larval and juvenile blue mussels (Mytilus edulis) at the transcriptomic, metabolomic, and whole organism levels. Blue mussels inhabit coastal areas, where they face climate-induced reductions in nearshore salinity. Despite their ecological and economic importance, scientists do not fully understand the underlying transcriptomic and cellular mechanisms of the osmotic stress response in blue mussels or how the ability to respond to stress changes throughout development. Blue mussels spend the first weeks of life developing through several larval stages in the plankton. These early life history stages are more vulnerable to environmental stress than juvenile or adult mussels, yet these stages are grossly understudied. Thus, an increased knowledge of how mussels at all developmental stages cope with low salinity is imperative for predicting how climate change will affect the distribution of M. edulis.

In a series of experiments, we evaluated adjustments of molecular, cellular, and physiological processes in larval and juvenile blue mussels during short-term, low salinity exposure to elucidate stage-specific divergence in the osmotic stress response. We found that larval mussels differ from juveniles in the composition of their metabolome and in the differential expression of genes involved in the stress response. These differences in the larval response to low salinity exposure likely play a role in the increased susceptibility of these stages to stress and suggest that larvae may need to expend more energy relative to juvenile or adult mussels to mount a response.

Additionally, we evaluated the effects of larval stress on later developmental stages and found that larval stress carries through metamorphosis and yields smaller juvenile mussels, potentially affecting the subsequent growth and size distributions of adult mussels. While larval exposure to low salinity generally had negative impacts on juvenile growth, there was evidence the previous exposure to stress may condition juvenile mussels for future low salinity events, depending on the timing of exposure. More studies on larval tolerance and the impacts of larval stress on juvenile fitness will be necessary for making accurate predictions of the effects of climate change on M. edulis distribution and abundance.

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