BALTIMORE (AP) -- Scientists say the health of America's largest estuary declined last year due to the effects of record-breaking precipitation.
Researchers at the University of Maryland Center for Environmental Science gave the Chesapeake Bay an overall grade of 46% for 2018, down from 54% in 2017. All of the indicators factored into the bay's health index declined or stayed flat last year. Its letter grade of "C'' is unchanged.
Last year's heavy downpours increased runoff sediments and more pollutants such as nitrogen and phosphorus washed into the water. The Baltimore area was deluged with 72 inches (183 centimeters) of rain, roughly 175% above normal rates.
Still, the annual report card released Tuesday stresses that overall trends show the Chesapeake improving significantly over years. Scientists say the bay's long-term health trajectory remains positive.