With Droughts and Downpours, Climate Change Feeds Chesapeake Bay Algal Blooms

Bennett McIntosh for the Office of the Dean for Research ・ High Meadows Environmental Institute

Nitrogen-rich agricultural runoff into the Chesapeake Bay presents an ongoing environmental and economic concern for the bay’s massive watershed. Pollution from fertilizer application feeds algal blooms that poison humans and marine life, and devastate fisheries.

While efforts to restore the bay have been successful during the past several years, a study led by Princeton University researchers shows that weather patterns tied to climate change may nonetheless increase the severity of algal blooms by changing how soil nutrients leach into the watershed.

Extreme rainfall cycles caused by increased climate variability flush larger amounts of nitrogen-containing nutrients from fertilizer and other sources into the Susquehanna River, which carries them into the Chesapeake Bay, according to a report in the journal Geophysical Review Letters. Moreover, a spike in rainfall can increase nitrogen levels in the bay even if the amount of fertilizer used on land remains the same.

These chemicals feed explosive algae growth that can produce toxins that harm people, fish, wildlife and drinking water. Decaying algae also suck oxygen from the surrounding water, creating a low-oxygen state known as hypoxia that results in “dead zones” that suffocate fish and other species important to the aquatic food chain.