Date of Award

Spring 4-17-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Heather J. Hamlin

Second Committee Member

Damian Brady

Third Committee Member

Nishad Jayasundara

Additional Committee Members

Paul Rawson

Robert Bayer

Abstract

Increases in anthropogenic input of carbon dioxide into the atmosphere have caused widespread patterns of ocean warming and ocean acidification. Both processes will likely have major impacts on commercial fisheries and aquaculture, with acidification posing a particular threat to many marine calcifying invertebrates. In the State of Maine, commercial fisheries landings and a growing aquaculture industry have a combined value in excess of $600 million, 75% of which is sustained by marine calcifiers. Moreover, the American lobster (Homarus americanus) supports the most economically valuable fishery in the Gulf of Maine and Atlantic Canada. Previous research has documented a strong link between lobster biology and ocean temperature, but it is unclear how H. americanuswill respond to a rapidly changing environment. Additionally, previous efforts have focused primarily on the direct effects of a changing climate on lobsters (i.e., changes in growth, survival, and calcification), with little emphasis placed on the potential for sublethal effects to impact the population.

In this dissertation, I explore the effects of increasing ocean temperatures and acidification on H. americanus to understand how environmental changes can alter the health and physiology in multiple life stages of marine calcifying invertebrates. In Chapter 1, I introduce the global patterns and effects of climate change on marine calcifiers and review the current state of knowledge of my study species. In Chapter 2, I discuss how exposure to warming conditions impacts larval development, with a focus on potential trade-offs between enhanced growth and developmental instability. In Chapter 3, I continue to explore the sublethal impacts of warming on larval lobsters by examining changes in gene expression patterns in postlarvae exposed to varying temperatures during development. Chapter 4 explores how short-term exposure to acidified conditions impacts subadult (50 – 65 mm carapace length) lobster thermal physiology, hemolymph chemistry, and stress levels, a relatively understudied yet crucial life history stage. Finally, Chapter 5 summarizes the overarching themes of the dissertation, and concludes by providing suggestions for future research efforts.

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