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si3.jpg (22125 bytes) Diatoms

Diatoms are the most numerous organisms on earth. They produce half the oxygen we breathe!

The gold color between the holes is due to microscopic oil droplets in these single-celled photosynthetic creatures. They live in the spaces between the grains of sand, in the surface of the beach.

The color of the piles around each outlet hole is normal for sand at this beach. The filter feeders that live in these holes separate the diatoms and detritus from the sand. The filter feeders eat the D & D, and expel the sand.

When water covers the beach, these diatoms would float to the nearest inlet hole and be eaten. So, this kind of diatom has evolved a defense. As water approaches they change their oil droplet to starch (specific gravity 1.0), and sink one centimeter into the sand. When the water leaves they change back to oil (specific gravity 0.7), and float back to the surface, where the sunlight is strong, to photosynthesize. 

And not to be outdone, Macoma balthica, the bent-nosed clam and most common clam at the Cove, has evolved an elephant-like trunk. Macoma dredges for dinner. It sucks up the sand, and separates the diatoms and detritus in its filters.

The bent-nosed clam and several other clams breath and eat through one hole in the sand. Can you see their openings?

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Revised Monday, February 18, 2008 02:25:50 PM