The Diatoms
Life inside a glass box. . .
The Bacillariophyta are the diatoms. With their exquisitely beautiful silica
shells, or frustules such as that of Odontella shown above at
right, diatoms are among the loveliest microfossils. They are also among the
most important aquatic microorganisms today: they are extremely abundant both in
the plankton and in sediments in marine and freshwater ecosystems, and because
they are photosynthetic they are an important food source for marine
organisms. Some may even be found in soils or on moist mosses.
Diatoms have an extensive fossil record going back to the Cretaceous; some
rocks are formed almost entirely of fossil diatoms, and are known as diatomite
or diatomaceous earth. These deposits are mined commercially as abrasives
and filtering aids. Analysis of fossil diatom assemblages may also provide
important information on past environmental conditions
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