Date of Award

12-2001

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Paul D. Rawson

Second Committee Member

Sara M. Lindsay

Third Committee Member

Bruce J. Barber

Abstract

Factors affecting the distribution of Mytilus edulis and Mytilus trossulus in the Gulf of Maine are of great interest because of the blue mussel's economic and ecological importance. Genetic surveys of blue mussel populations indicate that eastern Maine represents the southern distributional limit for M. trossulus but that M. edulis is common throughout the Gulf of Maine. Because hydrographic features in the Gulf of Maine confound temperature variation and larval dispersal patterns, the relative importance of these potential range-limiting mechanisms cannot be ascertained from the distribution of adult mussels. Given that larvae are more vulnerable than adults to temperature extremes, this study focused on comparing the effects of temperature on M. trossulus and M. edulis larval growth and survival. Molecular techniques were employed to detemine species identity of adult mussels collected fiom a mixed population in eastern Maine. Mussels were induced to spawn in the laboratory and larvae of both species were reared at 5, 10, 15 and 20°C for 30 days. Observations were made on larval mortality, growth and development. The results indicate that the effects of temperature are not identical for larvae of the two species, with higher mortality rates observed for M. trossulus at 5 and 20°C and higher mortality for M. edulis at 15°C. In addition, at 20°C M. trossulus larvae demonstrated decreased growth relative to M. edulis. Taken together, the growth and survival observations suggest that 5°C is sub-optimal for both species and that M. trossulus larvae may experience thermal stress at 20°C. These differences have important implications for mechanisms limiting the range of M. trossulus in the Gulf of Maine.

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