Biomass and Trophic levels

Even though plankton are some of the smallest organisms on the planet, they account for a huge proportion of the biomass in the oceans.

Food Web And Ratio     Trophic Levels

Food webs are made up of trophic levels (a step in the transfer of energy within the food chain).  As an one organism consumes another energy is lost (through excretion and respiration) reducing the energy available to the next trophic level.  This means that there are fewer organisms at the top of the food chain (for example, sharks) than at the bottom of the food chain (for example, phytoplankton).  This can be shown in a pyramid of biomass