<P> Since the photic zone is where almost all of the photosynthesis occurs , the depth of the photic zone is generally proportional to the level of primary production that occurs in that area of the ocean . About 90 % of all marine life lives in the photic zone . A small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges . </P>
where does primary productivity occur outside of the photic zone
deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges