The environmental integrity and sustainable productivity of the ocean, our coasts and coastal watersheds, and the Great Lakes play a central role in the well-being of all Americans. Every day, the marine environment supplies a multitude of products and services that enhance and support the lives and livelihoods of citizens. More than half of the United States population lives in coastal watershed counties, and these counties generate 58 percent ($8.3 trillion) of the Nation’s gross domestic product (GDP), even though they comprise only 25 percent of the Nation’s land area. Structured around six societal themes, this book recommends research priorities designed to advance our understanding of critical ocean processes and phenomena that are relevant to human health, economic well-being, environmental sustainability, adaptation to climate and other environmental change, and national and homeland security.