Evaluation of preventative algaecide treatments for cyanobacterial resting cells in sediments of a central US lake

Abstract

Kinley-Baird CM, Smith EF, Calomeni AJ, McQueen AD, Gusler GO, Boyer M, Decker KN, Clyde GA. 2023. Evaluation of preventative algaecide treatments for cyanobacterial resting cells in sediments of a central US lake. Lake Reserv Manage. 39:340–355.Cyanobacteria can overwinter in sediments of aquatic systems as resting cells and contribute to harmful algal bloom (HAB) resurgences. We evaluated field-scale preventative algaecide treatments in April 2022 in terms of effectiveness for decreasing viability of cyanobacterial resting cells, with the goal of minimizing planktonic growth in season. Two consecutive treatments of a granular peroxide-based algaecide (GreenClean PRO) were applied (48 h apart) in a Kansas, United States, lake. Treatments were applied to a 31.5 ha treatment zone, separated from a 12.9 ha control zone using a silt curtain. Treatment design was informed by laboratory algaecide efficacy experiments using site-collected samples. In-lake treatment performance was evaluated based on comparisons of planktonic cyanobacterial densities in the treatment and control zones measured every 2 weeks for 4 months, then monthly for 2 additional months. Other lines of evidence included resting cell densities and recruitment viability in sediments 3 d after treatments were performed. For 9 of 11 sampling events from May to October, average planktonic cyanobacterial densities trended lower in the treatment zone than in the control zone (ranging from 6 to 97% lower). Declines in sediment cell density and recruitment of resting cells in laboratory assessments were not measurable 3 d after treatments were performed. Additional studies will be necessary to strengthen the database supporting use of this management strategy. However, there may be an opportunity to expand the model for how algaecides are used to manage HABs more effectively and efficiently in freshwater resources.