How Can Infinitesimal Animals Be Geological Historians?

In my last post, I described the Bryozoans, animals that are so small, you can’t really see them without a microscope.  Yet these tiny creatures contain complete animal systems and exist in myriad, fascinating shapes.

         The Bryozoans have been subjects of early microscopic studies hundreds of years ago.  As such, they were mistaken for plants.  They have been subjects of more recent, advanced microscopy, when improved scopes, dissection, and slide preparation showed them to be animals.  They have been subjects of very recent molecular examination, when it became possible to study their relationships to one another with DNA data.

         And now, in a neat reversal, they have switched from being the subject of study, to providing data for a different scientific quest.  Some Bryozoans offer geological data about Antarctica. 

         Groups of similar species of Bryozoans have been found on the shores of both the Weddell and Ross Seas, which are now separated by 1500 miles of ice sheet in Antarctica that is 2 kilometers thick.  The similarity of the Bryozoan species suggests that at some point, perhaps 125,000 years ago, the ice sheet had melted, and there was a connecting seaway between the two Antarctic seas.

         So here are these Bryozoans, once again keeping up wonderfully with modern, scientific research.  What a wonderful phenomenon.