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Like the sands of time...
Submitted by Carol Larson on Tue, 06/18/2013 - 10:06
Unique, as small as a grain of sand, and extremely important as proxies for studying climate change, foraminifera are single celled organisms that have lived in all types of marine environments since the Cambrian time- 525 million years ago.
Micropaleontologists on the JR like Dr. Christina Belanger from the South Dakota School of MInes and Technology who is shown here often have very small samples of sediment to work with but sometimes tests of foraminifera can accumulate on the sea floor forming forminiferal oozes which can be found in thicknesses of up to 1 km.
During times when foraminifera evolved rapidly, scientists can use the types of forams they see as markers for different time periods, thus using forams to determine the ages of marine rocks. Scientists can also plot the abundances of different types of forams and use them as an indirect report, or proxy for the environmental conditions at the time they lived. This is valuable information for understanding the Earth’s past.
Can you imagine an organism that’s shell is so tough it can become perfectly fossilized and be discovered intact after 2-3 million years?
What makes them so hardy? Their shell or test for one. It surrounds and protects them and is as small as a grain of sand. Drives the micropaleontologists to their microscopes to see them! Their tests are composed of materials from calcium carbonate to sand grains.
Foraminfera are able to move and feed by using pseudopodia. Being single celled organisms their bodies contain protoplasm, which also assists with mobility as they can move it in and out of the test and use it to slide along like a snail.
Forams are categorized by their size, test shape and whether they are planktonic or benthic. Planktonic live in the upper ocean zone, and are only found in the open ocean. They are distributed worldwide and settle to the bottom when they die. Scientists study planktonic forams because they are indicators of ocean currents and climate. Benthic foraminifera are bottom dwellers and are in abundance on the ocean floor in sediments.
Christina studies benthic forams. Why does she find them so interesting? Because forams can tell us so much about the environment, she can use them to determine how environments changed over time. She can then compare those environmental changes to changes she sees in other animals-like clams and snails that are preserved in the sediments with foraminifera.
Benthic forams secrete their shells from calcium, magnesium and oxygen dissolved in seawater. This means that we can also examine the chemistry of their shells to gain clues about what the ocean water was like; for example, what temperature it was.
There are also naked foraminifera that don’t have shells of their own but borrow another foram’s test to live in, like a hermit crab.
Forams occur in great abundance in a wide variety of places and are highly sensitive to their environment. Sounds like human beings too!
Read how the study of benthic forams today helps to restore the Florida Everglades system.
Photo courtesy of John Beck, Joides Resolution photographer.