Algal Blooms in the Basin

The ICPRB is fielding calls about the blue-green algae that can create toxins that harm people and pets who come in contact with blooms. News stories about dogs dying after swimming in contaminated ponds and lakes are getting heavy circulation. Lakes Needwood and Frank in Montgomery County, Md., have annual blue-green algae blooms and people and pets should avoid contact with the water. Blue-green algae lives in the Potomac, but large blooms are not currently common.

Blue-green algae is capable of producing toxins that could be harmful, but does not always do so.MarylandVirginia, and the District of Columbia all monitor these blooms and welcome reports from the public. The Environmental Protection Agency  works on harmful algae blooms as well. Blue-green algae, also known as cyanobacteria, is just one type of algae. Many other kinds of algae, such as filamentous types that look like hair attached to rocks, do not produce toxins, although any blooms of algae indicate an imbalanced system usually high in nutrients. Algal populations are an important part of aquatic systems, but can cause problems when they grow rapidly out of control.

As a general rule, humans and pets should avoid water that is discolored, has a layer of algal scum on the surface, or has a strong odor.

While instances of blue-green algae seem to be growing with hotter, wetter summers, it has been much worse. Into the 1970s, the Potomac and Anacostia rivers in the District were covered by florescent green mats of blue-green algae every summer. The blooms greatly decreased as Potomac restoration efforts took hold.