Deep Sea

Kilometers below the surface, deep seawaters are cold and dark, but they are not sterile. Sinking detritus supports sparse populations of animal consumers, as well as bacteria and archaeons that feed on organic particles. Despite their limited biomass, deep-sea biomes exhibit high species diversity, as high as those of shallow marine communities. However, the composition of communities in deep-sea biomes differs relatively little from place to place, and so the total diversity of these environments is lower than that found within the photic zone. Dense animal populations occur locally on the deep seafloor, where hydrothermal vents expel fluids containing high abundances of hydrogen, hydrogen sulfide, and methane. These compounds support locally high levels of primary production by chemosynthetic bacteria, many of them present as symbionts within the tissues of vent animals.