When thinking of aquatic weeds in Kerr Lake and Lake Gaston, most of us are aware of the usual culprits such as Hydrilla. Another invader, however, might not be as well-known by lake users and residents and can have even more severe impacts than its counterparts.
Many of you will unfortunately begin to notice a dark black mat growing under water in parts of Lake Gaston over the next few weeks. The mystery plant is known by a number of common names including horse-hair algae, Mermaid hair, and Fireweed. The scientific name for the blue-green 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 southeastern lakes, including Lake Gaston.
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.
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 occur often resulting in fish kills. 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, chemical and biological control methods are not efficient at levels acceptable for treatment in waters used by the public. Effective herbicide use is hindered by the protective sheath present in Lyngbya. Grass carp prefer many other species to feed on other than Lyngbya and mechanical removal is very expensive and time consuming.
Although difficult to treat, you can often reduce the likelihood of Lyngbya establishing where you live. Here are just a few tips that could sway the odds in your favor:
- Refrain from fertilizing areas near the water as excess nutrients will be rapidly consumed by Lyngbya resulting in further growth.
- If you live on or near the Lake, ensure that your community septic system is working properly. Septic leakage, along with other poor land use practices, have often lead to excess nutrient loads being made available to Lyngbya.
- Detection is important in new areas: Lyngbya is normally easy to identify being hard to tear apart and appearing black, filamentous, and having a foul smell. It can easily attach itself to anything (Including boat lifts – see photo) and is extremely hard to remove. If you begin to see Lyngbya growing in areas not previously reported, please contact your aquatics extension associate through the information provided below.
For known locations of Lyngbya in Lake Gaston, please visit the NCSU Aquatic Weeds Mapping page posted in the web links and scroll to “Lyngbya”.
Photo provided by: Bruce Johnson
Web Links For Additional Information:
NCSU Aquatic Weeds Mapping
If you have questions please contact your Aquatic Extension Associate, Brett M. Hartis, at (919)-515-5648 or email at bmhartis@ncsu.edu.