The Deep Atlantic Ocean

The Atlantic Ocean is a long sinuous ocean which originated during the Mesozoic following the breakup of the supercontinent of Pangea. For most of its length, the eastern and western boundaries are clearly defined by land masses, except where it is separated from the Caribbean Sea and Gulf of Mexico by troughs and trenches. The northern and southern limits are more difficult to define. To the north we consider the Atlantic to include the subpolar Greenland and Norwegian Basins. These are linked hydrographically to the rest of the Atlantic, although they are isolated topographically by the ridge system extending between Greenland and Scotland. To the south, the boundary between the South Atlantic and Southern Ocean is generally defined hydrologically by the Subtropical Convergence around 40oS (e.g., Webb, 1996). In this chapter we review current knowledge about the distribution and ecology of organisms on the floor of the Atlantic Ocean from the continental slope to the abyss, and describe the environmental setting that they experience. We focus particularly on the North Atlantic, since the literature for this hemisphere is far more voluminous than for the South Atlantic. As with any large review, we have been selective in our coverage of the regional literature, concentrating on aspects with which we are most familiar, or which have received greatest attention from investigators. Our treatment of the Atlantic intentionally omits hydrothermal vent and seep settings, which are covered in Chapter 4 of this volume. Following a description of the environment of the deep Atlantic, and of the biological communities region by region, we have attempted to synthesize general patterns of faunal density and biomass, community respiration, bioturbation and succession.