Date of Award

Fall 11-17-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Richard Wahle

Second Committee Member

David Fields

Third Committee Member

Lawrence Mayer

Additional Committee Members

Spencer Greenwood

Abstract

Anthropogenic warming and ocean acidification are occurring as CO2 continues to accumulate in the atmosphere (OA). Few studies have evaluated the joint effects of elevated temperature and partial pressure of CO2 (pCO2)on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change (IPCC) predicted temperature and pCO2 for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well-studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I-III) and postlarvae (stage IV) reared at the temperature projected for the Northwest Atlantic by the year 2100 (19 °C) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in 16 °treatments. Larvae from the high pCO2 (750 ppm) treatment at 16 °C had significantly longer carapace lengths, and greater dry masses in stages I-III and C: N ratios in the postlarval stage than postlarvae from all other treatments. Postlarvae raised in the high pCO2 treatment at 19 °C had significantly higher feeding rates and swimming speeds compared to postlarvae from the other three treatments. Together these results suggest that projected end-century warming will have greater adverse effects than increased pCO2 on larval survival, however the interactive effects of increased temperature and pCO2 have an additive impact on larval metabolism and behavior.

To complement and expand upon our suite of results, we examined gene expression in postlarvae raised in each of the two pCO2 treatments at 16 °C. We selected 13 annotated genes of interest (GOIs) that were differentially expressed between postlarvae from the two pCO2 treatments. We found 11 GOIs related to cuticle formation that were significantly downregulated in postlarvae from the high pCO2 treatment, and two GOIs related to metabolism and stress response that were significantly upregulated. These preliminary results in tandem with our developmental, physiological and behavioral measurements provide insight into how H. americanus postlarvae compensate for the stresses of an end-century pCO2 and maintain successful development under these conditions. As is the case for most experiments of this nature, our results may have been biased by the fact that we were only able to conduct measurements on the small number of larvae that survived the rearing experiment. The results must therefore be interpreted with caution. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying genetic mechanisms that drive their ecology.

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