Sediment Facilitates Microbial Degradation of The Herbicides Endothall Monoamine Salt and Endothall Dipotassium Salt in an Aquatic Environment

Abstract

Endothall dipotassium salt and monoamine salt are herbicide formulations used for controlling submerged aquatic macrophytes and algae in aquatic ecosystems. Microbial activity is the primary degradation pathway for endothall. To better understand what influences endothall degradation, we conducted a mesocosm experiment to 1) evaluate the effects of different water and sediment sources on degradation, and 2) determine if degradation was faster in the presence of a microbial community previously exposed to endothall. Endothall residues were determined with LC-MS at intervals to 21 days after endothall application. Two endothall isomers were detected. Isomer-1 was abundant in both endothall formulations, while isomer-2 was only abundant in the monoamine endothall formulation and was more persistent. Degradation did not occur in the absence of sediment. In the presence of sediment degradation if isomer-1 began after a lag phase of 5-11 days and was almost complete by 14 days. Onset of degradation occurred 2-4 days sooner when the microbial population was previously exposed to endothall. We provide direct evidence that the presence and characteristics of sediment are of key importance in the degradation of endothall in an aquatic environment, and that monoamine endothall has two separate isomers that have different degradation characteristics.

Identification and preventative treatment of overwintering cyanobacteria in sediments : a literature review

“…Endothall-based algaecides bind with sediment (Reinert and Rodgers 1984) and may be sequestered when applying treatments in proximity to sediments. Additionally, endothall can degrade relatively quickly via microbial degradation and therefore contact time can vary considerably among different site conditions (Islam et al 2018). Interactions with sediment need to be considered during the selection of specific algaecide formulations and concentrations to be utilized in field treatments.…”