Explain how light and depth determine the distribution of organisms in marine ecosystems

Various environmental factors affect the marine ecosystem. These factors include light, oxygen levels, depth of ocean, salinity, density and pH. These factors are varies with depth in the ocean these factors will either support or limit the life processes of the marine organisms.

The region in the depth of ocean up to where light can penetrate is called photic zone which extends from few meters to 150 meters. Photosynthetic organisms such as phytoplankton and about 90% of all marine life lives in this zone.

In the deep ocean the pressure is very high so, organisms have to survive under extreme pressure. In the deep ocean organisms are small and with low metabolic rate.  

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme