Scientists Puzzled by Unkillable Biofilm on Jefferson Memorial

Posted on August 10, 2016

Biofilm on the Jefferson Memorial dome

A biofilm growing on the Jefferson Memorial has been described as unkillable by scientists who are trying to remove it from the monument. The National Park Service says the culprit is a colony of microscopic organisms that adheres to stone surfaces. A big part of the problem is finding a way to remove the biofilm without damaging the marble.

The Washington Post reports that the biofilm is part algae, part bacteria and part fungi. The dingy biofilm is most prominent and noticeable on the dome of the monument and around its base. The Post says the National Park Service has been experimenting with different cleaning solutions. They are even considering trying ozonated water and lasers to kill it. The biofilm is also seen on other monuments in D.C.

Catherine Dewey, chief of resource management for National Mall and Memorial Parks, says in a statement, "Treatment of biofilm is difficult, as there is no known permanent method for removing it, and we have to ensure that any treatment must not do further damage to the soft marble of the memorial nor encourage further growth,. We are testing a variety of treatment techniques to find the option that is least damaging to the stone, safe for the environment and visitors, and cost effective."

The Post story quotes Federica Villa, a microbiologist from Milan, who says the black color is produced by the organisms to protect themselves from solar radiation. Some expects think a reduction in pollution may be helping the colony of microorganism flourish.



Photo: National Park Service