Importance of phytoplankton

The food web



Photograph of fish killed by a red tide on the shore of Padres Island, Texas.

Dead fish washed onto a beach at Padre Island, Texas, in October 2009, following a red tide (harmful algal bloom). (Photograph ©2009 qnr-away for a while.)


Climate and the Carbon Cycle

Through photosynthesis, phytoplankton consume carbon dioxide on a scale equivalent to forests and other land plants. Some of this carbon is carried to the deep ocean when phytoplankton die, and some is transferred to different layers of the ocean as phytoplankton are eaten by other creatures, which themselves reproduce, generate waste, and die.

Diagram of carbon fluxes in the upper ocean.

Phytoplankton are responsible for most of the transfer of carbon dioxide from the atmosphere to the ocean. Carbon dioxide is consumed during photosynthesis, and the carbon is incorporated in the phytoplankton, just as carbon is stored in the wood and leaves of a tree. Most of the carbon is returned to near-surface waters when phytoplankton are eaten or decompose, but some falls into the ocean depths. (Illustration adapted from A New Wave of Ocean Science, U.S. JGOFS.)

Worldwide, this “biological carbon pump” transfers about 10 gigatonnes of carbon from the atmosphere to the deep ocean each year. Even small changes in the growth of phytoplankton may affect atmospheric carbon dioxide concentrations, which would feed back to global surface temperatures.

What are Phytoplankton?

Print this entire article