The low concentration of 
The low concentration of one type of these organisms in certain regions can be explained by the iron hypothesis of the grazing control hypothesis; those regions are known as HNLC regions. That type of these organisms emits dimethyl sulfide, which participates in a feedback loop regulating global climate according to the CLAW hypothesis. Regions with a limited range of resources support a large range of these organisms, a fact which is known as their namesake paradox because it seems to violate the competitive exclusion principle. Copepods and krill are examples of the "holo-" type, which spend their entire life cycle as these organisms, which are contrasted with nekton, or free-swimming organisms. FTP, name these drifting organisms which are a common food source for whales.
The low concentration of one type of these organisms in certain regions can be explained by the iron hypothesis of the grazing control hypothesis; those regions are known as HNLC regions.
plankton