'Rock Snot' Found in Youghiogheny River
11 June 2012
By Don Hopey
The Yough has "rock snot," a slimy, invasive alga that's even
worse than it sounds because it can thickly coat riverbeds and
kill native fish, freshwater mussels and aquatic insects.
And the slimy green tendrils aren't much fun to swim in or boat
through either, and that could affect recreational pursuits on the
Youghiogheny River, a heavily used whitewater boating and fishing
flow in Fayette County.
An aquatic biologist with the Delaware River Basin Commission,
Erik Silldorff, found the alga, also commonly known as didymo,
last month on large boulders in Ohiopyle State Park.
Mr. Silldorff, who has done extensive work with the alga in the
Delaware, was on a family vacation when he stopped for a swim and
noticed what for him was familiar looking alga. He took a sample
and the finding was confirmed June 1 by the Academy of Natural
"We are very concerned," Pennsylvania Fish and Boat Commission
executive director John Arway said. "Didymo can blanket a riverbed
and fill in spaces between rocks used by other species."
He said when didymo fills in all the nooks and crannies on a
riverbed it disrupts the "aquatic food chain pyramid" displacing
aquatic insects, crayfish and freshwater mussels that are food
sources for many fish species.
Beverly Braverman, executive director of the Mountain Watershed
Association, said the discovery of didymo is like a horror movie
for the river.
"It's like 'The Blob,' where this creepy thing grew from a single
cell and kept growing and growing," she said. "It's scary. This
will have a huge impact and no one knows how to stop it."
Native to cooler regions of Europe, Asia and North America,
didymosphenia geminata has been discovered in an ever widening
range over the past few decades and is now found in 11 states,
including New York and West Virginia.
Didymo was discovered in the upper Delaware River in 2007 and
later in Dyberry Creek in Wayne County.
Earlier this month state and federal aquatic biologists for the
first time found dense "blooms" of rock snot in the middle
Delaware, past its confluence with the Lehigh River, as far south
as Bucks County.
Didymo spores have also been found in the Delaware as far down
river as Trenton, New Jersey.
"We may not be able to eliminate didymo from an infected waterway,
but we can do our best to slow its spread and to prevent it from
spreading to other waters," Bob Morgan, a fish commission
ecologist who studies aquatic invasive species, said.
He said didymo cells can easily be carried downstream and picked
up by any equipment contacting the infected water, including
fishing tackle, waders, recreational equipment, and boats and
It takes only one live didymo cell to start a new colony of the
"We urge anglers and boaters to clean your gear before leaving a
water body and entering another one," Mr. Morgan said.
Don Hopey: email@example.com or 412-263-1983.