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Sea Sawdust: Earth Image of the Week November 19, 2010
Astronaut photo of Nile Delta
Bacteria and plankton can merge into great chains and mats, observable by satellites hundreds of miles up.
Some of the smallest organisms on Earth can gather in such concentrations that they can be clearly viewed from space.

Microscopic bacteria and plankton often merge in great chains and mats that are sometimes observed on satellite images and seen by astronauts orbiting aboard the International Space Station.

When NASA’s Aqua Satellite passed over the region just south of Fiji on October 18, 2010, such floating organic structures stretched across a wide area of the South Pacific.

NASA says that while it’s impossibly to identify exactly what species are seen in the image to the right, it is likely that the yellow-green filaments are long colonies of Trichodesmium, a form of cyanobacteria often found in tropical waters.

Cyanobacteria are aquatic and photosynthetic. That means they live in the water and can manufacture their own food, absorbing and using nitrogen from the open ocean and the air to fuel their growth.

In the process, they effectively fertilize the ocean for the world’s primary producers, phytoplankton, which form the center of the ocean food web.

Some prehistoric ancestors of modern-day Trichodesmium have the distinction of being the oldest known fossils, with some dated as more than 3.5 billion years old.

Charles Darwin described Trichodesmin, which sailors often call “sea sawdust,” during his voyage aboard the HMS Beagle in 1845.

Full story and image: NASA