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Phytoplankton bloom off Argentina
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Phytoplankton bloom off Argentina

February 23, 2011
One of the most important tools of an artist is the palette, the surface on which a painter arranges and mixes pigment to form the rich color transitions used to create a masterpiece. On February 15, 2011, the waters off the coast of Argentina resembled the palette of a creative artist, awash with bands, smudges and swirls of jewel-tone blues and greens, some bright and some whitened to a milky hue.

In this case, the palette is the deep blue water of the Atlantic Ocean and the colors come not from artist's pigments, but from nutrients, microorganisms and sediment. The swirls and streaks are caused by the blending of two strong offshore currents.

Microscopic organisms, called phytoplankton, contain colorful pigments, such as chlorophyll. When masses of phytoplankton bloom near the surface of the ocean, and when they reflect sunlight, a spectacular array of colors can be seen from space. The color varies for each species of phytoplankton as well as the depth at which they float.

Off the Patagonian coast, the Malvinas (Falkland) Current flows northward from the cold Southern Ocean while the Brazilian Current brings warm water southward. Where they collide, turbulent eddies and swirls form, carrying nutrients upward from the ocean bottom. As the nutrients rise and the sunlight filters downward, a rich layer of bountiful food, warmth and light forms, where phytoplankton bloom in abundance. Where the bloom occurs, the water is colored in long, thin bands along the continental shelf, and in swirls where the currents collide.

The Rio Negro flows into the Atlantic Ocean in this region, carrying sediment and nutrients which play a role in the colors of the palette. River nutrients feed the growth of the brilliantly-hued organisms, while the sediment itself colors the water. Sediment usually lends a tan color to water when it is near the surface and bountiful. As sediment sinks, it can appear blue or green. In this image, the sediment from the Rio Negro forms a shore-hugging halo of greens and blues as it stretches towards the open ocean, where the colorful bands of phytoplankton bloom.


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