There’s a whole world in Puget Sound that you can’t even see – kind of like Horton Hears a Who! Foraminifera, or forams for short, are tiny one-celled critters that may be small, but they help us learn a lot about the environment.
What are foraminifera?
Foraminifera, or forams for short, are single-celled organisms that live in the open ocean, along the coasts and in estuaries. Most have shells for protection and either float in the water column (planktonic) or live on the sea floor (benthic). Of the approximately 8,000 species living today, only about 40 species are planktonic, thus the vast majority of foraminifera live on the sea floor.
What size are they?
Foraminifera are generally less than 500 microns (½ mm) in size, though some tropical species can grow to 20 cm. Puget Sound species are generally small. Because they don’t have a wall around their cell membranes), they are extremely flexible and can change shape.
What does “foraminifera” mean?
The shells have hundreds of tiny holes called foramen, the Latin word for window. The organism pushes extensions of its cytoplasm called pseudopodia (or false feet) through these holes to gather food.
What do they eat?
Foraminifera eat detritus on the sea floor and anything smaller than them: diatoms, bacteria, algae and even small animals such as tiny copepods.
What eats them?
In turn, forams are devoured by grazing animals such as snails, sand dollars, sea-cucumbers and scaphopods (tusk shells).
How do they build their shells?
Forams are unusual among single-celled organisms because they build shells made of calcium carbonate (calcareous) or from tiny grains of sand stuck together (agglutinate). Despite their small size and relatively simple biology, forams build complex shells, consisting at their simplest of one chamber (like a vase or tube) to many chambers that coil in elaborate ways.
Where do they live?
Benthic foraminifera live in a number of different habitats at the sea bottom and most ‘crawl around’ using their pseudopodia. Some species live on the sediment surface (epifaunal) some within one or two centimeters of the surface (infaunal), some creep up stalks of seaweed or sea grass and others use organic “glue” to attach themselves to shells, stones, or even other forams.
Are there fossil forams?
When the foram dies, its shell may be preserved in the sea floor sediment where it becomes part of the fossil record as sediment turns to rock. Fossil foraminifera have been found in rocks as old as 500 million years, and it is highly likely they lived even further back. The Burke Museum has a large collection of fossil forams from West Coast marine sedimentary rocks.