Read the full story in the Washington Post.
Five decades ago, President Lyndon B. Johnson declared the polluted Potomac River a “national disgrace.” Although it is now much cleaner, officials in Washington are still not convinced the water is safe for humans to swim in.
But many miles downriver, where the Potomac widens to lakelike proportions as it flows toward the Chesapeake Bay, it teems with a different species of swimmers whose presence may signal healthier waters: dolphins.
During the past four years, researchers who study the common bottlenose dolphins swimming this part of the Potomac have hardly been able to keep up with their numbers. Dolphins are easily identified by their distinct fins or marks on their bodies, and in 2015, scientists identified about 200 individuals in one section of river off Virginia’s Northern Neck. Now they have counted well over 1,000 dolphins, which sometimes congregate in groups of more than 200.