BENEDICT - Walter Boynton knows all there is to know about the Patuxent River - how to find its guts and marshes, where it shifts from suburban stream into bay-like vastness, when the tide is slack and when it rises.
But you don't need to be a University of Maryland biologist to see that the river is in trouble. As Boynton steers his boat underneath the Route 231 bridge near this Charles County town, a thin white film covers the water - part of a miles-long algae bloom.
He lifts a dredge from the water to examine a sample of the bottom. His crew recoils at the stench, like that of rotten eggs. Nothing is living in this muck - none of the small clams, crabs or oysters that used to make the river their home. It is the deadest part of a dead zone, with oxygen levels far below what's needed to sustain life.
"Frankly, in all my years, I don't ever remember seeing the oxygen that low here," said Boynton, 61, a researcher at the university's Center for Environmental Science. Nitrogen pollution is feeding the noxious algae, which suck oxygen from the water and suffocate creatures below.
In the 25 years since Maryland, Pennsylvania and Virginia signed a historic agreement to clean up the Chesapeake Bay, the three states and the federal government have spent several billion dollars on the effort. Yet, the bay in many respects is as bad as or worse than when they started. Maryland researchers give its water quality a score of 40 out of 100 - a far poorer grade than the 55 it got for 1986.
The degradation of Maryland's rivers is a main reason for this decline. In Anne Arundel County, bacteria and nitrogen from human waste pour into the Severn River from thousands of septic tanks. In Southern Maryland, development now lines the shores of the Patuxent, sending nitrogen-laden runoff into the river. On the Eastern Shore, fertilizer from farms continues its assault on the Choptank.
Maryland's leaders have long blamed other states for the Chesapeake's problems. They point out that much of the bay's pollution flows in from the Susquehanna River, largely from Pennsylvania farms. Another source is the Potomac, which meanders through Virginia, West Virginia and Washington.
But several of the bay's most impaired rivers are almost entirely within Maryland. And the blame for their precarious health, scientists say, rests squarely on the shoulders of state and local politicians who have allowed harmful land-use practices to flourish.
