This indicator is only measured in the Assabet River, where biomass has been a particular problem, damaging the river’s ecology, wildlife habitat, scenery, and recreational values. Excessive growth of aquatic plants is a recognized problem in the watershed, particularly in impoundments created by dams on the Assabet River. Floating aquatic biomass includes filamentous green algae, duckweed, and rooted aquatic plants that reach the surface. Reduction in aquatic biomass is a key goal for the Assabet as stated in the TMDL prepared by MassDEP: “For the purpose of this TMDL, a substantial reduction in total biomass of at least 50% from July 1999 values is considered a minimum target for achieving designated uses.” OARS surveys floating biomass in three impoundments in the Assabet every August. Coverage amounts are compared to the 1999 values and scored accordingly.