Biomass accrual and trace-element concentrations in water and periphytic algae at select locations in the Clark Fork and Blackfoot Rivers, Montana, 2015

The U.S. Geological Survey monitored algal biomass accrual and concentrations of metals and other trace elements in stream water and periphytic algae at 3-4 day intervals over a 2-week period at 3 locations within the upper and middle portions of the mining-impacted Clark Fork River, Montana, and at one location on the relatively unimpacted Blackfoot River tributary. This data release makes available trends in major and minor trace element concentrations in surface water and periphytic algae, and corresponding trends in concentrations of autotrophic (chlorophyll a) and heterotrophic (ash-free dry mass) algal biomass collected in late July and early August 2015.