Pollutants that fuel algae blooms have decreased in New Jersey streams since the 1970s while chlorides from road salt increased, scientists found in a study released Feb. 27.

The U.S. Geological Survey (USGS) analysis of 28 monitored streams found that total nitrogen and total phosphorus either dropped or remained flat from 1971 to 2011. Chloride concentrations nearly doubled, however, at the four sites where data was collected.

The report found only two stations—one near Toms River and the other at...