So far from the coast: is protection needed for pelagic habitats and species?

The pelagic environment is the area of the ocean from the surface to just above the sea floor and includes all the physical and chemical conditions and biology in the water column. This environment forms the largest habitat on Earth, constituting 99% of the biosphere volume (Angel, 1993). Pelagic ecosystems account for nearly half of the photosynthesis on Earth through phytoplankton (Field et al., 1998) and supply >80% of the fish consumed by humans (Pauly et al., 2002). These ecosystems also play a major role in the pace and extent of climate change via the uptake of carbon dioxide and its removal to the deep ocean through the biological pump, and via the dynamics of the overturning circulation within the solubility pump (Hays et al., 2005).

While the open ocean can be divided into a number of vertical zones (Figure 14.1), here we collectively refer to these zones as the pelagic environment, and focus on the upper 200 m of the water column where the majority of the life in the pelagic zone resides and where most human activities occur. Note that the benthopelagic region includes the sea floor, and is not a focus of this chapter, as benthic protected areas typically encompass only the immediate overlying water, or are located in shallow coastal regions where ocean processes do not occur. In shallow or coastal regions, the whole water column may be considered benthopelagic.