Important because these vertical movements eventually bring nutrients from the deep to the shallow ocean. Salinity Salinity of ocean varies, depending on evaporation and runoff from land. Oxygen Water salt or fresh, holds much less oxygen than air. In ocean, oxygen is usually highest near the surface. Too little light below that, but there is life even at 10,000 m.
Open oceans have extremely low productivity.
The Shallow Ocean Oceanic productivity is concentrated in shallow waters, partly because nutrients are washed into the water from nearby land, partly because the shallow water allows nutrients to be retained within the community instead of sinking to the bottom of the deep, deep ocean. Mainly N of Tropic of Cancer, S of Tropic of Capricorn. Prefer rocky shores. Kelp is a type of brown algae. Kelp beds have a complex vertical structure, like a forest.