USACE Philadelphia District
Published June 28, 2023

The U.S. Army Corps of Engineers’ (USACE) Philadelphia District is updating the harmful algal bloom status at Blue Marsh Lake from a Watch Status up to a Harmful Algal Bloom Advisory Status. 

  • Please be aware of the presence of moderate levels of blue-green algae, or cyanobacteria, in the lake and the potential for harmful toxins to be present. Visitors are advised to be alert for harmful algal bloom conditions and to avoid contact with discolored water or scum.
  • To protect yourself, your family, and your pets from blue-green algae blooms:
  • Avoid water contact in areas where the water is discolored or where you see foam, scum, or mats of algae on the water’s surface.
  • Children and pets are especially susceptible to the harmful effects of the toxins produced by blue-green algae. Do not allow children or pets to play in or drink scummy water.
  • If you have contact with water that might contain harmful cyanobacteria, rinse off with fresh water as soon as possible afterwards.

Learn more about Harmful Algae Blooms and their associated risks by visiting

For additional information, please contact the Park Office at 610-376-6337.

Scott Sunderland

Release no. 23-015