What is Filamentous Algae?
Filamentous algae are connected algae cells that grow and form long threads or filaments When growth is
large mats can form that stretch from the river bottom to the surface and cover significant portions of a river
reach. The term “Filamentous Algae” refers to any number of species that can be found in rivers and streams.
are numerous species of algae that are native to West Virginia and that can be found at any one location.
Impacts of Filamentous Algae Blooms
Filamentous algae blooms can interfere with designated uses of a river – typically water contact recreation and
public water supply. The following pictures display the extent of the problem in some impacted rivers:
If entities supplying public drinking water have an intake located in an area of a filamentous algae bloom, they
commonly receive complaints about the odor and/or taste of the water, requiring additional treatment and
expenditures. Recreational activities, such as swimming and fishing, can be impacted by the excessive algae, and
lessen one’s ability to enjoy state rivers and streams.
Recreational Activity and Filamentous Algae in West Virginia Streams
Questions have been raised concerning how filamentous algae in West Virginia streams and rivers impacts and
ultimately may limit recreational activities. Activities like swimming, fishing and boating support a significant
tourism industry and are a critical economic driver in numerous regions of the state. As important as this issue is,
it is very difficult to adequately measure and quantify impacts. To address this question, DEP sponsored a survey to
measure the level of tolerance residents have to varying amounts of filamentous algae in state streams. The survey
was conducted by the research firm Responsive Management, and a copy of the final report, which includes the methods
and results of the study, can be found here.
What Causes Filamentous Algae to Bloom?
Nutrients – primarily nitrogen and phosphorus – when in excess are directly available and allow normal background
levels of algae to grow into excessive blooms. Flow conditions and river water chemistry also influence when and
where a bloom may occur. Sources of the excessive nutrients vary by watershed, from point sources such as waste
water facilities to non-point sources including urban or agricultural runoff.
What is the DEP Doing to Address Filamentous Algae Blooms?
DEP is monitoring numerous rivers in the state for filamentous algae blooms, including the Greenbrier, Tygart, South
Branch of the Potomac and the Cacapon rivers. The Watershed Assessment Branch (WAB) has developed Standard Operating
Procedures (SOPs) for measuring filamentous algae in streams and rivers. The SOP can be found in the
Periphyton/algae collection procedures section of the SOP document. WAB has also completed
numerous special studies
on the algae issues in the Greenbrier River and these studies can be found on the Special Studies Web page. When
adequate information is collected that determines blooms are impacting the uses of a stream or river – DEP will
consider listing the waterbody as impaired and putting it on the 303(d) list. The DEP has developed a listing
methodology for determining algae impairments that can be found here. Once listed, DEP will develop a TMDL or take
other actions to address the sources of pollution contributing to the algae blooms. Annual stream nutrient-algae
monitoring and assessment reports can be found here.
What can I do if I see Algae Blooms?
DEP staff cannot be everywhere, and input from the public can greatly assist in our understanding of filamentous
algae blooms, including when and where they happen. So if you see something that resembles a filamentous algae
bloom, here is how you can help:
- Document the time and place - the more specific the description the better, but even a general location is
- A picture speaks volumes - the more the better.
- Let us know what type of activity you were doing; swimming, fishing, boating, kayaking, etc. Did the algae
impact your activity?
Contact DEP Staff
James P. Summers, Environmental Resources Analyst
West Virginia Department of Environmental Protection
Division of Water and Waste Management
601 57th St. SE
Charleston, WV 25304
Phone: (304) 926-0499 x43890