ANNAPOLIS, Md. (AP)- An annual report on the Chesapeake Bay says pollution from unusually heavy rains last year contributed to the first decline in a decade in the overall health of the nation’s largest estuary.

Chesapeake Bay Foundation President Will Baker said Monday the bay “suffered a massive assault last year,” when large amounts of debris were flushed into the bay, mostly from Pennsylvania. The bay’s grade sank from C-minus to D-plus, which is the first decline of a grade in a decade.

According to the report, more significant rain storms could be the “new normal.”  That means more pollution running off farm fields and city streets into the bay and its rivers and streams.

But not all is bad news, according to CBF’s Director of Science and Agricultural Poicy Beth McGee.

“The good news is that scientists are pointing to evidence of the bay’s increased resiliency and ability to withstand, and recover from, these severe weather events. And this resiliency is a direct result of the pollution reductions achieved to date. In addition, we did see increases in scores for dissolved oxygen and bay grasses since 2016, but the recovery is still fragile.”

The 2018 State of the Bay report also noted that recent studies show an improving trend in underwater dead zones.