Chesapeake Bay Getting Better - Maybe

Study Finds Signs of Improvement in Chesapeake Bay

Efforts to reduce pollution of the Chesapeake Bay are starting to pay off, a major new study says, finding that despite weather-driven ups and downs, the "dead zone" that stresses fish and shellfish every summer has actually shrunk, on average, in recent years.

The study, published in the current issue of the scientific journal Estuaries and Coasts, appears to explain away recent research finding no real improvement in the "dead zone," where oxygen levels in the bay drop so low each summer that fish and shellfish struggle to survive. The oxygen gets sucked out of the water by the breakdown of massive algae blooms that grow every spring, fed by sewage, farm and urban runoff and air pollution.

The size of the dead zone in early summer has actually been getting worse, on average, in recent years, recent research had found. That was puzzling and troubling to scientists, who'd wondered why the zone wasn't shrinking in response to pollution reduction efforts. Water sampling has tracked long-term declines in algae-feeding nitrogen flowing into the bay from the Susquehanna River, the Chesapeake's largest tributary.

But looking at the dead zone in late summer, the researchers found that since the mid- to late 1980s, it has gotten smaller overall and broken up a little sooner each year.

"On average, the late summer [mid-July through August] dead zone volume in the last decade was about 80% of the volume in the mid-1980s," Rebecca Murphy, a Hopkins doctoral student who is the study's lead author, said in an email. The improvements roughly parallel declines in nitrogen measured in the Susquehanna, she said.

On a scientific level, Kemp, who has been studying the bay for 30-some years, said he was glad the new study resolved doubts about whether the Chesapeake is responding as other water bodies have to reductions in nutrient pollution. "After all this scratching of heads and beating our heads against the wall, we just realized it was right there, had been there all along," he said. Kemp called that twist "embarrassing" but also reassuring.

This is good news, if true, and I'm inclined to believe it.  However, there's a whiff of post-hoc about this finding.  Having agreed ahead of time that the test for the improvement of the Bay as a result of nutrient reduction was a reduction in the overall size of the dead zone, the statistics failed to prove that out.  However, upon looking around, and finding that the "no change" scenario was actually composed of a worsening in spring and a bettering in summer, they decided after the fact (post hoc) that the true test of the improvement was the improvement in late summer.  How convenient...

Now based on their alleged success in improving the Bay this relatively small amount, they are asking you to trust them that with massive disruptions in agriculture, and other changes, they can produce similar continuing improvements in the future.