This summer, as in summers past, we’ve heard and read reports of the disturbing “dead zones” that afflict as much as 41 per cent of the main stem of the Chesapeake Bay. But now, more systematic and careful monitoring is revealing similar, oxygen-deprived areas in some of the loveliest rivers, including the Severn.
At the very least, these lifeless patches are a bad omen for the people who live along the Severn’s shores and for the rockfish, perch, crabs and other creatures that struggle to breathe in its waters.
I got a first-hand look at some of these areas recently with John Page Williams, the senior naturalist for the Chesapeake Bay Foundation. His home in Arnold overlooks the Severn and he has been monitoring the river’s health for decades. In 1993, he took me and a camera crew from CBS Sunday Morning out on the Severn for a report on the water quality of the Chesapeake. Now we were retracing portions of the same route 16 years later.
“We didn’t understand dead zones as well back then,” he said, as he and my wife, Susy, and I set out from Chase Creek on the northeast shore in “First Light,” the 17-foot Boston Whaler that serves as his floating water-quality testing platform.
The center console of his little boat bristles with antennas and LCD screens — there is hardly room to set a water bottle in all the high-tech clutter. He carries six fishing rods, a 16-foot-long pole to probe the bottom, buckets, anchors, rubber boots and crab and fish nets. First Light is a workhorse, not a showhorse.
It was a sunny, comfortable day with a gentle breeze and the Severn looked gorgeous as we motored upriver. On the southwestern shoreline, kids frolicked and splashed on the beach at Sherwood Forest. To the east, a huge, 16,000 square-foot house dominated a bluff. “That used to be the biggest house on the river,” Williams said. “Now there are houses half-again as big.”
John Page eased the engine back as we reached a midpoint in the river. We drifted a bit and then the first of several dead zones became vividly apparent on the screen of his Lowrance sounder.
From the surface down to a depth of 30-plus feet, the water was alive with fish. Below 35 feet, nothing moved. The screen was blank. “There is very little oxygen down there,” Williams said, “so fish and just about everything else is forced up the water column into water that is warmer than they would normally choose to be in.”
A quarter-mile up the river, we stopped again, this time cutting the engine altogether and drifting. Williams pulled out one of his favorite teaching tools, a hand-held Yellow Springs Instruments water-quality meter. Using a sensor at the end of a long, weighted cord, it measures the dissolved oxygen and salinity levels in the water, as well as the temperature.
As Williams slowly eased the sensor overboard, the screen blinked and told the story: at the surface and down six or seven feet, the brackish water had seven parts per million of dissolved oxygen, more than enough to support fish. At a depth of 13 feet, the oxygen in the increasingly salty water was reduced by half, making it perilous for fish and barely suitable for crabs.
At 26 feet, the water was “dead,” with only a trace of dissolved oxygen.
“Nothing can live at that level,” Williams said, frowning at the meter. The screen showed the same results all the way down to the bottom, which was 39 feet at that spot. “Pretty ugly,” he muttered.
What robs the Severn of oxygen and life?
“Runoff, essentially, on this now-suburbanized river,” Williams said. “The nitrogen and phosphorous from the fertilizer on our lawns, and, God forbid, the stuff that comes through our stormwater drains.
This super-sized meal of nutrients that we are feeding the Bay, especially after a heavy rain, nourishes fast-growing plants, like algae, which in turn decompose and suck up the oxygen. It is not a complicated process, just deadly.
Why should we care? Two reasons: the dead zones are a sign of a fundamentally unhealthy body of water, along which we choose to live and play. Second, because the dead zones reduce the livable habitat for the rockfish and perch and crabs and oysters that we love to harvest from the Bay.
And, needless to say, the deterioration of water quality in the Severn is being matched in many of the Bay’s other rivers and tributaries.
It is true that there have always been oxygen-deprived areas in the Bay. They existed 400 years ago when Captain John Smith first explored these waters. In those days, natural runoff from the forested shores decomposed on the bottom and sucked up oxygen. But the scale of the dead zones was negligible compared to what we are generating today.
“We’ve asked this river to adapt to us humans for a long time,” Williams said as we motored back to Chase Creek. “Now it is time for us to adapt our life styles to it.”
And, indeed, there are some hopeful signs. Across from the Sherwood Forest shoreline, there is a rich bed of luxuriantly healthy underwater grasses that Williams points to as a sign of recovery. “These grasses died out around 1980,” he said, “and came back in 1994 and have been growing ever since. They are a symbol of the essential paradox of the Chesapeake: some things are getting better, while others are getting worse.”
John Page Williams is not the only person monitoring the Severn. Pierre Henkart, a semi-retired scientist who lives on the river has been taking samples for Fred Kelly, the Severn Riverkeeper, every 10 days or so this summer from the Naval Academy to above Round Bay.
“I’ve been amazed at the dead zones we have found,” he said, “even in relatively shallow creeks, with as little as six feet of water. We have repeatedly found dead zones at the bottom of Round Bay. That startled me.”
As it should.