In an open ocean, the biomass of primary produceres (microscopic algae) is often lower than the biomass of higher trophic levels (zooplanktons and fish), as illustrated below by an inverted pyramid of biomass. How can there be enough food in an open ocean to suppor the higher trophic levels?

Answer: BSolution: In an open ocean, the large numbers of phytoplankton quickly complete their life cycles and sets of new propulation or crops of phytoplankton are formed every few hours or days. Thus, the cumulative energy contents that these generation after generation of phytoplankton trap in course of a year is certainly much more than trapped by only a few generations of of herbivorous fishes in the corresponding time and space.