American Water Resources Association

Spreading of the Invasive Alga, Didymosphenia geminata ("Rock Snot"), in the Delaware River Basin

  • 18 Oct 2012
  • 11:30 AM - 1:30 PM
  • One Parkway Building, 1515 Arch Street, 18th Floor Conference Room, Philadelphia, PA
  • 85


(depends on selected options)

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Spreading of the Invasive Alga, Didymosphenia geminata ("Rock Snot"), in the Delaware River Basin

Erik Silldorff, Ph.D.

Aquatic Biologist

Delaware River Basin Commission

West Trenton, NJ

Didymosphenia geminata (also known as "Rock Snot") is an invasive, aquatic alga that can form extensive mats in streams, rivers, and lakes. Since 2007, the stalk-forming variety of D. geminata has been found in the East Branch and West Branch Delaware River and the mainstem Delaware River as far downstream as Callicoon, NY.

In April 2012, large stalked blooms of D. geminata were found extending largely beyond the contaminated areas identified in 2007, i.e., over a 40-mile stretch of the Delaware River including portions of the Upper Delaware Scenic and Recreational River and the Delaware Water Gap National Recreation Area. Additional surveys showed that D. geminata extended south from the Delaware Water Gap National Recreation Area, over a section of the river known as the Lower Delaware National Wild and Scenic River (DRBC, Press Release, April 24, 2012).

Although D. geminata is not a public health hazard, it raises great ecological concerns. In rivers and streams, D. geminata forms light brown or whitish mat, sometimes up to 20-cm thick. These mat blooms adversely affect fish, plant, and invertebrate species, altering stream ecosystem functions. In addition to environmental issues, the species poses serious economic concerns for fisheries, tourism, irrigation, and hydropower.

Engineers:  This seminar does qualify for 1.0 Professional Development Hour (PDH).  A Certificate of Attendance will be available on site for AWRA-PMAS members only.  The meeting price for non-members who wish to receive a 2012 Certificate of Attendance for the PDH is $10.00 ($3.00 for meeting + $7.00 for certificate).  Please note: all registrations for lunch orders close by noon on the day before the presentation.  Thank you!

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