Abstract
From the surface, the world’s oceans appear vast and boundless. Ocean currents, which can transport marine organisms thousands of kilometers, coupled with species that spend some or all of their life in the pelagic zone, the open sea, highlight the potential for well-mixed, panmictic marine populations. Yet these ocean habitats do harbor boundaries. In this largely three-dimensional marine environment, gradients form boundaries. These gradients include temperature, salinity, and oxygen gradients. Ocean currents also form boundaries between neighboring water masses even as they can break through barriers by transporting organisms huge distances. With the advent of next-generation sequencing approaches, which allow us to easily generate a large number of genomic markers, we are in an unprecedented position to study the effects of these potential oceanic boundaries and can ask how often and when do locally adapted marine populations evolve. This knowledge will inform our understanding of how marine organisms respond to climate change and affect how we protect marine diversity. In this chapter I first discuss the major boundaries present in the marine environment and the implications they have for marine organisms. Next, I discuss the how genomic approaches are impacting our understanding of genetic connectivity, ocean fisheries, and local adaptation, including the potential for epigenetic adaptation. I conclude with considerations for marine conservation and management and future prospects.