6ebbba77_Marine_habitats__principles__Living_in_the_sea
[Factor] Light [Living on the land] Light is very important to plants. Light quantity is almost constant over large areas. The mountains have brighter light and more ultraviolet. There is more light above water than below. [Living in the sea] 
Light is very important to seaweeds. The quantity and quality of light are very variable and change with depth, amount of plankton and particles, waves, foam. It gives rise to many different habitats. Deeper than 70m in clear oceans, plants can no longer photosynthesise enough to stay alive. Along the coast, this is 15-25m. Runoff from the land makes this worse.
Marine habitats, principles
Living in the sea