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.