A bloom of decaying algae with major ecological
ramifications was recently observed by NASA’s Multi-angle
Imaging SpectroRadiometer instrument on the Terra satellite.
The event occurred near Elands Bay, in South Africa’s Western
Cape province.

Approximately 1,000 tons of rock lobsters beached
themselves during February 2002, when the decay of this dense
bloom of phytoplankton caused a rapid reduction in the oxygen
concentration of nearshore waters. The lobsters, or crayfish
as they are known locally, moved toward the breaking surf in
search of oxygen, but were stranded by the retreating tide.
The effects of the losses on the maritime economy are expected
to be felt over the next few years.

The colors of the newly released images, taken by the
instrument’s nadir camera on February 2 and 18, have been
accentuated to highlight the algal bloom, or red tide. The
images can be viewed at:


The two views show the shoreward migration of the algal
bloom. Each image represents an area of about 205 kilometers
(127 miles) by 330 kilometers (205 miles). Elands Bay is
situated near the mouth of the Doring River, about 75
kilometers (46 miles) northeast of the jutting Cape Columbine.

The term “red tide” is used to refer to a number of
different types of phytoplankton blooms of various hues. The
wine color of certain parts of this bloom are consistent with
the ciliate species Mesodinium rubrum, which has been
associated with recurring harmful red tides along the Western
Cape coast. Under these conditions, however, the lobsters
were not poisoned, and people came from across South Africa to
gather them for food.

The Multi-angle Imaging SpectroRadiometer, built and
managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif.,
is one of several Earth-observing experiments aboard Terra,
launched in December 1999. The instrument acquires images of
the Earth at nine angles simultaneously, using nine separate
cameras pointed forward, downward, and backward along its
flight path. More information about the radiometer is
available at http://www-misr.jpl.nasa.gov


JPL is a division of the California Institute of
Technology in Pasadena.