<P> Depending on how deep the sea is, the pelagic zone can extend over up to five horizontal regions in the ocean . From the top down, these are: </P> <P> From the surface (MSL) down to around 200 m (660 ft) </P> <P> This is the illuminated zone at the surface of the sea where enough light is available for photosynthesis . Nearly all primary production in the ocean occurs here . Consequently, plants and animals are largely concentrated in this zone . Examples of organisms living in this zone are plankton, floating seaweed, jellyfish, tuna, many sharks and dolphins . </P> <P> From 200 m (660 ft) down to around 1,000 m (3,300 ft) </P>

What two components make up the epipelagic zone at the surface