City nature challenge at Mallows Bay

City nature challenge at Mallows Bay Photos uploaded to iNaturalist help record biodiversity in the sanctuary. (Image credit: Taylor Schneider/NOAA) Download Image May 26, 2026 For the fourth year in a row, Mallows Bay-Potomac River National Marine Sanctuary participated in the worldwide City Nature Challenge that occurred from April 24 to 27, 2026. The City Nature Challenge is a friendly collaboration among cities all over the world to share observations of nature using the iNaturalist app.