A Walk Through Time

Fabulous Forams

580 Million Years Ago

Foraminifera ("forams" for short) are aquatic protoctists whose cells are enclosed in loose-fitting, hard, shell-like covers called tests. Found throughout the world's oceans, tests provide clues to the past. The are key biomarkers for oil companies looking for layers from the "right age" for drilling. Their presence in the desert means an ocean once covered the area. Different species of forams are very fussy on choosing their habitats; their fossils help us "read" the nature of paleoenvironments.

Foram individuals are small, but as a group they are a mighty force. The calcium carbonate of their abundant tests affects the global carbon cycle. Forams of the past unite, their tests make up the sedimentary rock of the great Egyptian pyramids and White Cliffs of Dover.

The "spots" on these living forams are their photosynthetic symbionts. (Photography by Esmeralda Caus, top, and by David Caron, bottom three photos, Woods Hole Oceanographic Institution)

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