The white rings found on many rocks in the James River haven’t gone away, though the recent rains may change that. JRNH got an answer from James River Park manager Ralph White and now Rex Springston of the Richmond Times-Dispatch picked up the story and found a few more opinions on what is causing the rings.
Paul Bukaveckas, a VCU algae expert, said it’s possible the James River rings are caused by calcium or other minerals in algae that attach to the rocks. If the river level drops — as it did much of this winter — the exposed algae would dry up, leaving the minerals behind. The rings would be at the bottom of the boulders, Bukaveckas said, because the rocks’ higher parts aren’t under water long enough for algae to form.