Transmision electron microscope image (enlarged some 3,000 times) of a section of a fecal pellet collected by a sediment trap in the North Atlantic. It includes undigested, phytoplankton cell organelles, including chloroplasts. The blue (artificially colored) areas represent remains of coccoliths that were eaten by a zoolankter and passed unaffected through the gut. Coccoliths are composed of nearly pure calcite, the heaviest mineral produced by marine organisms, which makes a fecal pellet heavy enough to settle rapidly through the water column. (Susumu Honjo)[back]
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