Mouth of the Mississippi

Credit: NASA Image by Robert Simmon, based on Landsat data provided by the UMD, Posted on: Wednesday, 11 August 2004, 06:00 CDT Download full size image

The Mississippi River drains the heart of the North American continent,? carrying vast quantities of sediment and depositing it along the shore of Louisiana and into the Gulf of Mexico. The sediment is composed of topsoil, sand, dead and decaying plants, and anything else washed away by a strong rainstorm far upstream. Many of these effluents are nutrients that act as fertilizer for the microscopic plants (phytoplankton) living near the surface of the Gulf waters. Each summer the phytoplankton population explodes, fueled by the long summer days and the nutrients supplied by the Mississippi. A similar effect occurs in a stagnant pond choked with algae (a common type of phytoplankton). As the phytoplankton age, die, and decompose, bacteria absorb oxygen dissolved in the water, creating a dead zone along the shore at the ocean bottom. The oxygen-poor water is deadly to animals, from the microscopic zooplankton that graze on phytoplankton to crustaceans, molluscs, and fish.

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