ANNAPOLIS — Biologists Andrew Watts and Alice Volpitta navigated the muddy, junk-strewn waters of the Chesapeake Bay, testing water quality and finding out just how much dirt and debris the remnants of Tropical Storm Lee dumped into the bay.
Stopping their small boat near the mouth of the Patapsco River recently, Watts and Volpitta, who work for the Maryland Department of Natural Resources, tested water clarity by measuring the Secchi depth, or how deep a disk could be dropped before it disappeared.
“Less than 0.1 meter,” Volpitta announced, while Watts recorded.
It was the dirtiest water Watts had sampled in the bay in his four years with DNR.
“I’ve seen rivers that were dirty like this. But this is the main stem of the Chesapeake Bay. It’s not supposed to be like this,” Watts said.
The relentless rain caused by Lee swelled the Susquehanna River and other bay tributaries to historic levels, and officials are concerned that the resulting influx of nutrients and sediments could harm aquatic life.
“What we could see is a loss of underwater grasses,” said Scott Phillips, Chesapeake Bay Coordinator for the U.S. Geological Survey. “That’s because the water’s going to be so cloudy from all this sediment. And in fact there’s so much sediment it actually might bury some of the grasses.”
That includes grasses in the Susquehanna Flats, which have made a comeback in recent years, Phillips said. Underwater grasses are important because they provide habitat and food for much of the bay’s life.
“The impacts from Tropical Storm Lee are extremely significant,” said Bruce Michael, director of resource assessment at DNR.
Besides grasses, oyster beds may also be buried by sediment.
“We’re hoping the oysters will be able to withstand this amount of sediment,” Michael said.
Calling Lee a “hundred-year event” — causing the third highest river flow at Conowingo Dam, where the Susquehanna enters the bay, since the USGS started keeping records — Michael said DNR will be doing additional monitoring cruises to assess its impact.
And it is only the latest event in an unusually wet year.
“This year, we had extremely high flows during the spring,” Michael said. “We actually had probably our annual amount of precipitation and flow coming over Conowingo Dam by the end of May that we see in an entire year. And of course what we’re seeing now just adds on to this.”
The timing of Lee, coming at the end of summer when there is less biological activity in the bay, means it will have less of a long-term impact than if it had occurred earlier in the summer, Michael said.
Hurricane Irene also caused an influx of sediments and nutrients into the bay after pushing Maryland tributaries such as the Choptank River to record flow levels. But Irene also had a positive effect, helping rid the bay of its huge underwater “dead zone” earlier than usual.
The dead zone — a swath of low-oxygen water where fish, crabs, and oysters can’t survive — emerges every summer, when nutrient pollution fuels oxygen-depleting algae blooms, and fades every fall. But this year, Irene’s high winds mixed the water layers and allowed oxygen to reach the bay’s depths.
“That’s about the only good thing” that came of Irene, Michael said.
On Wednesday, Watts and Volpitta profiled the water column, taking a reading every meter from the bottom to the surface, to see whether the dead zone was still gone.
Dissolved oxygen was 3.6 milligrams per liter at the bottom, compared to 8.4 at the surface. A month ago the oxygen reading would have been 0.0 or 0.1 at the bottom, Watts said.
“The hurricane did stir up the water, so those dead zones are basically gone until next year,” he said.
Steering a path north of the Bay Bridge, Watts and Volpitta contended with the ubiquitous trash that had been swept into the bay along with sediments and nutrients.
Near the mouth of the Patapsco, Watts saw something that was unusual even on a day when 55-gallon drums, plywood and whole trees had bobbed threateningly in his path.
It was a half-sunken boat, its back torn off and its bow underwater. The name “Maria” was visible on the hull.
Before calling the U.S. Coast Guard to report it, Watts steered his own boat alongside the wreck to take a look inside. Nestled among grass and logs, he found a minnow bucket in good condition. He placed it in his boat, saying his one at home was “all busted up.”
“I was looking for good trash all day,” Watts said. “Still didn’t find that suitcase full of money though.”