What’s an environmental learning center focused on native ecology to do when faced with a nonnative, invasive plant choking one of its ponds? This situation required expert guidance and, in this case, Aquascape Environmental stepped up the most effective solution possible. However, the road to conquering the invasive pest was not without a few twists and turns.
The Chattahoochee Nature Center (CNC) is nestled northeast of Atlanta, just across the road from the Chattahoochee River in Roswell. The 127-acre property hosts camps, classes, and educational events, and features native plant gardens, several ponds, wetlands, woodland trails and resident wildlife (full-time animal inhabitants are injured and non-releasable). The CNC offers visitors of all ages with unique opportunities to experience and interact with nature.
How did an invasive species get in here?
Unfortunately, one of the CNC’s three lakes–known as the Kingfisher Pond–had a substantial infestation of aquatic weeds that caused it to become very unsightly. Aquascape Environmental was contacted to assist the CNC to develop a plan to address this problem. We identified the offending species as Eurasian Watermilfoil, a non-indigenous aquatic species that is known for aggressively displacing native aquatic plants, decimating natural diversity and wildlife habitat in the water body. As its name suggests, the native range of Eurasian Watermilfoil is Europe, Asia, and North Africa, and it was most likely introduced to North American waterways by the aquarium trade. The species is still uncommon in Georgia; when it occurs locally, it has most often been introduced unintentionally by dumping of aquarium fish and/or plants into a water body.
While the ecosystem impact was the primary concern in this instance, the visual negative impact of Eurasian Watermilfoil clogging the pond (see Figure 2) was also a significant concern for the nature center, which hosts hundreds of visitors each week. The most effective and efficient removal method for the Eurasian Watermilfoil would include an application of an EPA-approved aquatic herbicide. Aquascape Environmental proposed treatment options using controlled dosage of aquatic herbicides approved for management of Eurasian Watermilfoil. While the CNC understood the need for the treatment, the staff expressed reservations about introducing any herbicide into an element of their natural ecosystem. Of particular concern were the center’s resident beavers and Bald Eagles, the latter of which are subject to stringent environmental protections as an endangered species.
The search for sustainable solutions to preserve the ecosystem
Given the CNC’s concern, another option was presented for the stocking the pond with triploid grass carp (Ctenopharyngodon ). “Triploid” refers to grass carp bred with an extra set of chromosomes to ensure sterility to ensure the lack of reproduction of the fish. Triploid grass carp are an effective control method for submersed aquatic plants; since the grass carp are strictly herbivorous, and they do not disturb the other fish or wildlife in the water body. Only sterile grass carp may be legally stocked for biological weed control in Georgia in order to reduce the impacts to the native ecosystems. The CNC decided to go with this option as the method of controlling the nuisance aquatic vegetation.
Unfortunately, shortly after the carp were stocked in the pond, river otters took up residence in Kingfisher Pond. The arrival of otters wasn’t a complete surprise, given the Chattahoochee Nature Center’s proximity to the Chattahoochee River, a natural otter habitat. The downside in this case was that the species of otter making a home in Kingfisher is known to prey on grass carp. Over time, the otters decimated the carp population, making the fish ineffective as a long-term method of controlling the Eurasian Watermilfoil.
When it is necessary to use herbicide
The following summer, the invasive aquatic plant was back in a big way, and it was now clear that a herbicide treatment was going to be necessary to save the pond. Our team worked closely with CNC, to develop an appropriate treatment plan based on the special conditions involved. Three treatment options, incorporating different products, application rates, and timeframes. The pros and cons of each to the CNC staff and Board, and ultimately all parties agreed to a treatment option that provided an acceptable comfort level regarding impact to the resident wildlife as well as a high confidence level that the treatment would be effective.
With a plan in place, we coordinated the treatment option application with the CNC staff in order to satisfy all concerns
Two months later, the CNC staff reported that the treatment “appeared to have had a positive impact on the invasive material,” with no known impacts to the resident wildlife. “The team at Aquascape Environmental was wonderful to work with,” CNC staff noted. “The 46-year-old mission of the Center and sensitivity to the site were always the primary concerns in all management proposals they recommended. It was a very positive process all the way around.”
