"Plant" Profile - Lyngbya

We are definitely working our way into the heat of summer here at AERF.  Those in the business of aquatic plant management as well as those who just enjoy the water, often deal with the usual invasive culprits like Hydrilla, Eurasian Water Milfoil, and Water hyacinth during the time of year. Another invader, however, might not be as well-known, especially by those of us who recreate this time of year.  Our plant profile this week isn't really even a plant at all, but rather a cyanobacteria (blue-green algae).  This blue-green usually rears it's ugly head in the heat of summer and can have even more severe impacts than its well known invasive plant counterparts.

During the early spring, those on the water may begin to notice a dark black mat quietly growing under water in parts nutrient rich waters. The mystery plant is known by a number of common names including horse-hair algae, Mermaid hair, and Fireweed.  Fast forward to the warm months of summer, and as if over night, the black mats make their way to the surface, becoming an eyesore and much more.  The scientific genus name for this summer blooming, benthic algae is “Lyngbya”. Lyngbya is a filamentous cyanobacterium (algae-like plant) composed of cells surrounded by a very tough sheath. Its hair-like strands crowd together in thick, tangled mats which can occur along the bottom of the lake or floating. There are more than sixty known species of Lyngbya that occur in both marine and freshwater environments. Most of the freshwater forms are harmless; however there is at least one noxious form of Lyngbya present in our lakes.

Photo Credit:  NCSU Aquatic Weed Management Program

Lyngbya wollei or Giant Lyngbya is an extremely aggressive form of Lyngbya that can result in literal tons of plant material in a relatively small area. Lyngbya resembles human hair and is most often black in color until late summer when it turns a blotched green, black, and white. Lyngbya needs abundant nitrogen, phosphorus and dissolved organic solids to thrive, therefore it is often found in dense mats at the bottoms of nutrient rich lakes. During the warmer summer months, Lyngbya produces gasses during photosynthesis that cause the mats to rise to the surface yielding unsightly sludge that blocks navigation and shades out native vegetation. This is the reason Lyngbya can be very hard to discover and track. Often by the time it is noticed floating at the surface, filaments have had a head start growing along the bottom of the Lake.

Photo Credit:  Bruce Johnson

There are very few to no benefits of having Lyngbya wollei in a water body. It robs nutrients from otherwise beneficial plants while also reducing sunlight and decreasing dissolved oxygen. Unlike some of the invasive weeds like hydrilla, Lyngbya provides NO structure for fish and other organisms as it grows as a flat mat along the bottom until rising. Once the giant mats begin to decay, severe depletion of dissolved oxygen can potentially occur. The plant also deters people from boating, fishing or swimming in the area due to its unsightly appearance and production of a raw sewage-like smell.

To make things worse, Lyngbya wollei is extremely difficult to control. Current physical and biological methods of control are not efficient and chemical control can be difficult to achieve in certain wayer use situations. Effective herbicide use is sometimes hindered by the protective sheath present in Lyngbya as well as variations across water bodies. Grass carp prefer many other species to feed on other than Lyngbya and mechanical removal is very expensive and time consuming.

For more information on the control of lyngbya wollei and other cyanobacteria, and other nuisance algae, visit our Best Management Practices Handbook, chapter 13 page 97.

Stay tuned for more of the latest in aquatic plant science, management, and innovation!  If you would like to make a nomination for our AERF Spotlight or Feature Focus Friday, please contact Dr. Brett Hartis at bmhartis@ncsu.edu.

For more information on AERF, visit our website! 

Cover photo Credit:  NCSU Aquatic Weed Management Program

*This article expanded upon by author from original post in the Lake Gaston Guide.