Biodiversity and climate change in the oceans

The ocean is a vast and varied habitat for organisms, and contains most of the known phyla and at least 250,000 species. Patterns of biodiversity vary by depth, habitat type and region, with numerous hotspots of diversity of particular taxa, such as fishes. Patterns of fish diversity globally, and their sensitivities to climate change, need to be understood to predict the future of biodiversity and fisheries. This chapter describes key climate change stressors that can affect fish populations, assemblages and therefore biodiversity at many scales. We describe how sea temperature, through fish physiological processes, may act as a selective agent, while pressures such as disease and changing habitat, which can also be related to climate change, can drive biodiversity loss. We describe and compare approaches to understanding changes in ocean biodiversity, including risk modeling and direct empirical observations. We end with a case study to illustrate how changes in ocean biodiversity and fisheries can be linked to climate change via a modeling approach.