(Electron microscope photograph by Jeremy Young)

It is not always possible to identify the type of phytoplankton present using spacebased
remote sensing. Coccolithophores, however, are a group of phytoplankton that are
identifiable from space. These microscopic algae armor themselves with external plates
of calcium carbonate. Called coccoliths (a ball of which is shown above magnified
13,000 times), these plates can give the ocean a milky white or turquoise appearance
during intense blooms. A ball of coccolith plates surrounds each coccolithophore algae
cell. Typically there is a single layer of about 10 coccoliths around the cell, but some
cells accumulate multi-layered coccospheres with hundreds of coccoliths. The long-term
flux of coccoliths to the ocean floor is the main process responsible for the formation of
chalk and limestone. (reference: Marine Phytoplankton Blooms edited by David L. Alles Western Washington University). (http://earthobservatory.nasa.gov/Study/Coccoliths/)