Prevailing winds, density differences, and the rotation of Earth on its axis all influence both surface and deep ocean currents, which also influence the biosphere. Explain how upwelling, thermohaline circulation, the Coriolis effect work and how they influence the availability of nutrients available in the surface waters. And describe how nutrient availability impacts photosynthesis and the ocean food web.

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.