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Underwater Grasses Double in Chesapeake Bay, But Now Face New Threat

Tom Pelton

It’s a warm afternoon on the Chesapeake Bay, with a light breeze and the clouds piled high, and Brooke Landry, a biologist with the Maryland Department of Natural Resources, is in a skiff motoring toward Marshy Creek.

After weaving between channel markers, she finally reaches a cluster of floating islands of underwater grasses.  It’s a dense jungle, with seedpods projecting from the surface like clusters of grapes. Hundreds of minnows dart between the branches and a Chesapeake stingray glides past.

Landry, chair of the Chesapeake Bay Program’s aquatic vegetation research workgroup, reaches down into the forest and pulls up a handful of plants.

 “The one I’ve got in my hand right now is Elodea canadensis, Canadian waterweed,” she says, fingering a feathery shaft. “It’s a lovely, beautiful plant. The second one I managed to grab was redhead grass, Potamogeton perfoliatus. It’s different from a lot of grasses in the bay because it has these small, maybe one inch long leaves that grow alternately all the way up the stalk.”


Underwater grasses are both the best single indicator of the Chesapeake Bay’s health and one of its strongest engines of improved water quality.  Grasses filter out sediment, produce oxygen, and provide shelter for a galaxy of life forms.

After declining sharply in the early 1970s, and then two decades with little real  improvement, the extent of underwater grasses in the Chesapeake Bay has suddenly more than doubled over the last five years, according to data from aerial surveys led by the Virginia Institute of Marine Science (VIMS). The amount of aquatic vegetation in the bay expanded from 48,000 acres in 2012 to 97,000 acres last year – the largest amount since monitoring began in the 1980s.

Now, to be clear, the recovering grass beds are still just a fraction of their historic coverage, which might have been 600,000 acres, according to VIMS researchers.  And underwater grasses frequently get buried in mud by major storms, as happened in 2011 with Tropical Storm Lee and Hurricane Irene.

But there is no question the grasses are on an upswing since 2012.  What’s the cause?  For the first time in years, water clarity in the bay has been improving and algal blooms declining, according to annual report cards by the University of Maryland Center for Environmental Science. The clearer water allows light to penetrate to the bottom, which – in turn -- allows submerged aquatic vegetation to photosynthesize and spread.

Landry and scientists in Virginia have concluded that the driving forces behind the improvement are legal, numeric limits on pollution in the bay imposed by the Environmental Protection Agency in 2010.

“Mainly what we are hoping to attribute it to is the Total Maximum Daily Load, the pollution diet,” Landry said of the EPA pollution limits. “That has restricted the amount of nutrients – the phosphorus, nitrogen and sediments – that go into the water. All of the Chesapeake Bay watershed states have agreed to reduce their pollutants, and a lot of best management practices have been put in place. The water is clearing up as a result, and that’s helping the SAV come back.”

Robert Orth, a professor at VIMS who leads the annual project to conduct aerial surveys of bay grasses, agreed with Landry’s analysis.   "I think it's pretty impressive, and I think it speaks a lot to the fact that we think that the efforts to clean up the bay, the TMDLs, probably are working,” Orth told the (Hampton Roads, Virginia) Daily Press.

The twist in the encouraging plotline for the bay is this:  The Trump Administration earlier this year chose an administrator for EPA, Scott Pruitt, who – as Oklahoma Attorney General – filed a lawsuit to challenge these EPA pollution limits, which were opposed by the farm lobby and developers. The administration is also proposing to eliminate all funding for the Chesapeake Bay Program that Landry works with.

A bipartisan group of lawmakers from the bay region are fighting these cuts. Whether they succeed or fail may decide whether the great comeback of the Chesapeake’s underwater forests continues or sinks.

Tom Pelton, a national award-winning environmental journalist, has hosted "The Environment in Focus" since 2007. He also works as director of communications for the Environmental Integrity Project, a non-profit organization dedicated to holding polluters and governments accountable to protect public health. From 1997 until 2008, he was a journalist for The Baltimore Sun, where he was twice named one of the best environmental reporters in America by the Society of Environmental Journalists.