Photos uploaded to iNaturalist help record biodiversity in the sanctuary. (Image credit: Taylor Schneider/NOAA)
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. Participants upload photos of the plants, animals, and fungi that they see, where it gets recorded in iNaturalist while crowd-sourced data helps identify the species. Each year, the City Nature Challenge provides a snapshot of global biodiversity, with millions of observations of tens of thousands of different species across the world recorded over one weekend.