Post by Victoria Starnes.—From 2014-2018 an extreme annual drawdown was implemented on Bluff Lake on Noxubee National Wildlife Refuge starting in July and ending in December to increase moist soil plant production areas and improve feeding opportunities for waterfowl and waterbirds. Although these practices were initially successful in providing forage for waterfowl, American lotus (Nelumbo lutea) and alligator weed (Alternanthera philoxeroides) began to cover the lake (see images below: a top down view of a central region within Bluff Lake before treatment).

Although these plants are native, they tend to quickly shift diverse plant communities toward densely aggregated monocultures.To make things worse, according to the Moist-Soil Management Guidelines for the U.S. Fish and Wildlife Service Southeast Region, both alligator weed and American lotus have no nutritional value for waterfowl (https://www.fws.gov/columbiawildlife/MoistSoilReport.pdf). That means, if refuge managers did not reduce the spread of these nuisance plants within Bluff Lake, they could be reducing their ability to provide forage for waterfowl in the future. Dense aggregations of vegetation can also make launching boats at access points and fishing near banks increasingly difficult. Which can result in a frustrated angling community (see images below, left: Loakfoma Lake Noxubee National Wildlife Refuge, right: image of mud motor in lotus from https://www.louisianasportsman.com/).

After alligator weed and American lotus began taking over the main pool of Bluff Lake, refuge managers decided to put a stop to it. In July of 2019 herbicide was sprayed on approximately 250 acres of Bluff Lake (see image below, credit: USFWS

The herbicide application was a great success in the short term, and drastically reduced the amount of lotus and alligator weed in the main pool of Bluff Lake (see image below: a top down view of a central region within Bluff Lake after treatment). However, there are still areas that were not treated which are densely covered by vegetation. These strongholds for lotus and alligator weed could quickly recolonize the lake. To prevent this from happening, additional treatments are planned for fall of 2019 and 2020.

After treatment, much of the lotus and alligator weed within Bluff Lake began to decompose (see image below, credit: USFWS). When these plants decay it reduces the amount of dissolved oxygen in the water. If the water was then drawn down, oxygen levels could be further reduced. This in turn could stress fish which could lead to a large fish kill. To prevent this from happening, the U.S. Fish and Wildlife service has decided to suspend future drawdowns on Bluff Lake until treatment of Lotus and alligator weed is completed in the fall of 2020.