As the basis of the marine foodchain, phytoplankton are important
indicators of change in the oceans. These marine flora also extract
carbon dioxide from the atmosphere for use in photosynthesis, and play
an important role in global climate. Phytoplankton blooms that occur
near the surface are readily visible from space, enabling a global
estimation of the presence of chlorophyll and other pigments. There are
more than 5,000 different species of phytoplankton however, and it is
not always possible to identify the type of phytoplankton present using
space-based remote sensing.
Coccolithophores, however, are a group of phytoplankton that are
identifiable from space. These microscopic plants armor themselves with
external plates of calcium carbonate. The plates, or coccoliths, give
the ocean a milky white or turquoise appearance during intense blooms.
The long-term flux of coccoliths to the ocean floor is the main process
responsible for the formation of chalk and limestone.
This image is a natural-color view of the Celtic Sea and English
Channel regions, and was acquired by the Multi-angle Imaging
SpectroRadiometers nadir (vertical-viewing) camera on June 4, 2001. It represents an area of 380 kilometers by 445
kilometers, and includes portions of southwestern England and
northwestern France. The coccolithophore bloom in the lower lefthand
corner usually occurs in the Celtic Sea for several weeks in summer. The
coccoliths backscatter light from the water column to create a bright
optical effect. Other algal and/or phytoplankton blooms can also be
discerned along the coasts near Portsmouth, England, and Granville,
At full resolution, evidence of human activity is also apparent in
this image. White specks associated with ship wakes are present in the
open water, and aircraft contrails are visible within the high cirrus
clouds over the English Channel.