As on land, so in the sea, autotrophic plants are the basis of all life. ii Sessile plants live on a narrow fringe along coasts only, so, if we wish m to consider the amount of matter produced by plants of the sea, we II must confine our attention to planktonic algae, which are found everywhere in the upper oceanic water masses. It is the organic matter synthesized by phytoplankton out of purely inorganic substances by means of light which directly and indirectly serves as food for all organisms in the sea, from the smallest bacteria to the largest whale.
Nielsen, E. S.. 1955. "Production of organic matter in the oceans." Journal of Marine Research 14, (4). https://elischolar.library.yale.edu/journal_of_marine_research/850