Pelagic zone

The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth.

[1] The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom.

Marine life is affected by bathymetry (underwater topography) such as the seafloor, shoreline, or a submarine seamount, as well as by proximity to the boundary between the ocean and the atmosphere at the ocean surface, which brings light for photosynthesis, predation from above, and wind stirring up waves and setting currents in motion.

The pelagic zone refers to the open, free waters away from the shore, where marine life can swim freely in any direction unhindered by topographical constraints.

The benthic zone is the ecological region at the very bottom, including the sediment surface and some subsurface layers.

Nearly all primary production in the ocean occurs here, and marine life is concentrated in this zone, including plankton, floating seaweed, jellyfish, tuna, many sharks and dolphins.

[citation needed] The name is derived from Ancient Greek ἄβυσσος 'bottomless' - a holdover from times when the deep ocean was believed to indeed be bottomless.

[7] Some examples of pelagic invertebrates include krill, copepods, jellyfish, decapod larvae, hyperiid amphipods, rotifers and cladocerans.

Thorson's rule states that benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to widely dispersing pelagic larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring.

[citation needed] Many species of sea turtles spend the first years of their lives in the pelagic zone, moving closer to shore as they reach maturity.

Examples are the Atlantic puffin, macaroni penguins, sooty terns, shearwaters, and Procellariiformes such as the albatross, Procellariidae and petrels.