Although some red tides form a healthy part of phytoplankton
production, recurrent harmful or toxic blooms also occur,
with results depending upon the type of plankton and on
atmospheric and oceanic conditions. At Elands Bay in South Africa's
Western Cape province, about 1000 tons of rock lobsters beached
themselves during February 2002, when the decay of dense
blooms 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 Multi-angle Imaging SpectroRadiometer's nadir camera acquired
these red, green, blue composites on February 2 and 18, 2002,
during Terra orbits 11315 and 11548. The colors have been accentuated
to highlight the bloom, and land and water have been enhanced
separately. The two views show the shoreward migration of the algal
bloom. Each image represents an area of about 205 kilometers x
330 kilometers. Elands Bay is situated near the mouth of the
Doring River, about 75 kilometers 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 algal blooms along the Western Cape coast. Under these
conditions, the lobsters are not poisoned. During the recent
event, government and military staff transported as many of the
living lobsters as possible to areas that were less
affected by the red tide. At the same time, people came from
across South Africa to gather the undersized creatures for food.
The effects of the losses on the maritime economy are expected
to be felt over the next few years.
MISR was built and is managed by NASA's Jet Propulsion Laboratory,
Pasadena, CA, for NASA's Office of Earth Science, Washington, DC.
The Terra satellite is managed by NASA's Goddard Space Flight Center,
Greenbelt, MD. JPL is a division of the California Institute of
Technology.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
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