ASSESSING TRANSCRIPTOMIC AND PHYSIOLOGICAL RESPONSES OF ENVIRONMENTAL STRESS IN MUSSELS (MYTILUS EDULIS) FROM TWO SITES AND SIZES TO DISCOVER MARKERS CAPABLE OF MONITORING MUSSEL HEALTH

Abstract

The Prince Edward Island blue mussel (Mytilus edulis) aquaculture industry is being challenged by climate change induced environmental stressors, that is impacting mussel health and survival. Physiological responses of mussels to stress have been evaluated in many studies, however, less is known about how transcriptomic response leads to physiology. The present thesis aimed to first, study the transcriptomic response of acute stress related to hypoxia, hyposalinity, food availability (low/high), then to design markers capable of detecting early stress response. Two sizes (adult, seed) and sites (March Water, St. Mary’s Bay) of mussels from PEI were evaluated to understand similarities and differences in transcriptomic response to stress. Transcriptomic response in each stressor was evaluated using an RNA-seq approach, to understand total mRNA expression occurring during acute stress. Specific markers were discovered associated with each stressor, and underwent optimization and validation, using RT-qPCR. RT-qPCR expression of markers was normalized, and then statistical analysis was completed to understand the expression between the treatments and different mussel sizes and sites. The results of this study found that transcriptomic response was highly variable between sizes, sites and individuals in each stressor evaluated. Marker optimization, verification and statistical analysis further validated this, as expression was found variable between mussel sizes and sites. Markers should be further evaluated in a real world setting to see if they could be effective in detecting the stressors at different time points. Variability in transcriptomics uncovered the complexity related to stress response and was hypothesized to be related to baseline differences between the sizes and environmental differences between the two sites.