–by Joan Treichel, SRA Science Reporter

If you love your Severn River, please be very cautious about fertilizing your lawn this spring. Although fertilizers are remarkably valuable in feeding the world’s populations, when they end up in the Chesapeake Bay or the rivers that flow into it, they can inflict grave damage.

What can be done to solve this gargantuan problem?

The major solution is to prevent fertilizer runoff from farms and from impervious surfaces such as parking lots into the water in the first place. But if fertilizer does end up in the water, oysters and wetlands can help counter the problem somewhat.

So reported Jeffrey Cornwell, PhD, a research professor at the University of Maryland Center for Environmental Science, during a recent virtual presentation at Cafe Scientifique in Annapolis, Maryland. His presentation was based on science conducted not only by himself, but by numerous other environmental scientists, he noted.

Here’s how fertilizers exert their damage if they end up in water, Cornwell explained. Nitrogen and phosphorus in fertilizers feed algae blooms. The algae blooms in turn deplete oxygen from the water, especially on the river and creek bottoms where the dead algae accumulate year after year. And when “you ruin the bottom of water, animals cannot live there.” Goodbye rockfish, goodbye crabs, so long oysters!

What progress is being made in preventing fertilizer runoff into the Bay and its tributaries?

Quite a bit in Maryland, somewhat less in Virginia, and least in Pennsylvania, where fertilizer runoff from farmlands into the Susquehanna River is a major offender, Cornwell pointed out.

“Actually Maryland is one of the most progressive areas in the world trying to prevent fertilizer runoff,” Cornwell stated. But nonetheless, fertilizer runoff is an ongoing threat even in the Maryland area.

If fertilizers do end up in the Bay and its rivers, oysters can help temper their pernicious impact by sucking up nitrogen and phosphorus in the fertilizers, Cornwell explained. As a result, efforts are being made to repopulate oysters in the Bay and its rivers.

“We are moving toward oyster restoration as a best practice in 2021,” he noted. But alas, “they are no magic bullet” for solving the fertilizer problem, he admitted, because even though they can help remove nitrogen and phosphorus from the water, the amount they can remove pales with the amount of nitrogen and phosphorus being poured into Bay from various sources.

Wetlands, too, can help sop up nitrogen and phosphorus from the water, Cornwell continued. “Wetlands are doing a lot of work for us for free.” But again, their success cannot begin to offset the amount of fertilizer running into the Bay and its rivers.