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Ecological Roles and Impacts of Large Cetaceans in Marine Ecosystems
Joe Roman, Jeremy Kiszka, Heidi Pearson, Matt Savoca and Craig Smith
The ecological role and importance of marine animals, from sea otters to large whales, have received increased focus in recent years. As the largest animals ever to have existed on the planet, whales are expected to have top-down impacts on their prey, but their influence on communities and ecosystems is a relatively new area of research. In this report we discuss the state of the science for the consumptive and nonconsumptive effects of whales, including their role as predators, prey, and influence on behavior-mediated impacts. Whale carcasses also provide nutrients and deep-sea habitat for hundreds of species, including more than 100 endemic animals, several of which rely on chemosynthetic bacteria. Whales play a role as nutrient vectors in at least two ways: during their vertical movement between foraging dives and rest and respiration at the surface and during long-distance migrations from high-latitude foraging areas to winter grounds, where several species calve and breed. Whales can also make physical changes in the oceans, through benthic and bubble-net feeding and swimming through the pycnocline. Population declines from commercial whaling likely affected all of these processes, and threats, from climate change and increased industrialization of the ocean, are expected to have an impact in individual whales, whale populations, and their ecological roles.