Dissolved oxygen under waterhyacinth following herbicide application

• Published in: Journal of aquatic plant management Vol. 59; no. s; pp. 82 - 89
• Main Authors: Miskella, John, Madsen, John, Llaban, Angela, Hard, Edward
• Format: Journal Article
• Language: English
• Published: Gainesville Aquatic Plant Management Society, Inc 2021
• Subjects: 2,4-D; Agricultural research; Aquatic plants; Boating; Canopies; Canopy; Channels; Data loggers; Decomposition; Dissolved oxygen; Fish; Freshwater plants; Glyphosate; Habitats; Herbicides; Mass flow; Migrations; Navigation; Outlets; Oxygen; Plant cover; Resource management; State parks; Variance analysis; Vegetation; Water resources; Water resources management; Water temperature; Waterways; San Joaquin River Delta; Sacramento California; California; United States > US
• ISSN: 0146-6623; 0146-6623
• DOI: 10.57257/japm-20215982

The California State Parks Division of Boating and Waterways (CDBW) manages waterhyacinth [Eichhornia crassipes (Mart.) Solms] in the Sacramento–San Joaquin River Delta (the Delta) to ensure navigation and fish habitat. Decreasing the amount of waterhyacinth in the Delta should increase the proportion of oxygenated water for fish habitat and migration. However, some water resource management personnel are concerned that plant decomposition following herbicide treatment could temporarily lower the dissolved oxygen in the water under the plant canopy. The U.S. Department of Agriculture Agricultural Research Service and CDBW conducted an experiment in the summer of 2016 to monitor dissolved oxygen following herbicide treatment relative to untreated waterhyacinth canopies and open water. The experiment was conducted in two Delta environments. The first consisted of channels subject to tidal fluctuations and mass flow, and the second consisted of back-end sloughs, which have only a single outlet, where there was minimal water movement. Three channel-side sites were chosen and three 0.025-ha plots per site were randomly assigned to be treated with glyphosate or 2,4-D, or remain untreated. Three back end slough sites were chosen and three 0.25-ha plots per site were randomly assigned to be treated with imazamox, glyphosate, or 2,4-D, or remain untreated. A data logger measuring dissolved oxygen every 30 min was deployed under the canopy in each plot. Data was collected 2 wk prior to treatment through 6 wk after treatment. Data loggers were also deployed in the open water, away from waterhyacinth canopy, in the channels and in the back-end sloughs. The dissolved oxygen under waterhyacinth was consistently lower than in the open water. The dissolved oxygen levels pre- and post-treatment were compared for each treatment, using ANOVA (P 0.05). For the channel-side trial, there was no significant difference in dissolved oxygen levels for any of the treatments (P 0.18). In the back-end sloughs, there was no significant difference in dissolved oxygen levels for any of the treatments (P 0.92 for all comparisons). Herbicide treatments did not result in a significant decline in dissolved oxygen after treatment relative to pretreatment levels.