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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY BASED INTEGRATED MANAGEMENT OF INVASIVE AQUATIC AND RIPARIAN WEEDS

Location: Exotic and Invasive Weeds Research

Title: Mechanical Shredding of Water Hyacinth (Eichhornia crassipes): Impacts to Water Quality in the Sacramento-San Joaquin River Delta, California

Authors
item Greenfield, Ben - SF ESTUARY INSTITUTE
item Siemering, Geoffrey - SF ESTUARY INSTITUTE
item Andrews, Joy - CA STATE U - EAST BAY
item Rajan, Michael - CA STATE U - EAST BAY
item Andrews, Stephen - UC BERKELEY
item Spencer, David

Submitted to: Estuaries
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2007
Publication Date: August 1, 2007
Citation: Greenfield, B., Siemering, G., Andrews, J., Rajan, M., Andrews, S., Spencer, D.F. 2007. Mechanical Shredding of Water Hyacinth (Eichhornia crassipes): Impacts to Water Quality in the Sacramento-San Joaquin River Delta, California. Estuaries and Coasts. 30(4):627-640.

Interpretive Summary: We evaluated the water chemistry and nutrient effects of mechanical shredding of water hyacinth (Eichhornia crassipes) in an agricultural slough and a tidal wetland on the Sacramento-San Joaquin Rivers Delta, California. Shredding was conducted with two types of shredder boats in fall of 2003, and another boat in spring of 2004. Overall, shredding measurably affected water quality, but specific effects varied as a function of shredding site and season. Significant increases were observed for total Kjeldahl nitrogen and total phosphorus for all experiments. Dissolved oxygen impacts varied by site, decreasing after shredding at the agricultural slough but increasing at the tidal wetland. Calculations indicated that Delta-wide shredding operations could cause between 0.1% and 8.5% increases in the overall abundance of carbon, nitrogen, and phosphorus in the Delta water column. The local effects of shredding to control water hyacinth will vary widely as a function of site characteristics, but that Estuary-wide effects would be limited.

Technical Abstract: Management actions to control invasive aquatic species can have significant ecosystem-scale effects. We evaluated the water chemistry and nutrient effects of mechanical shredding to control water hyacinth (Eichhornia crassipes) in an agricultural slough and a tidal wetland on the Sacramento-San Joaquin Rivers Delta, California. Shredding was conducted with two types of shredder boats in fall of 2003, and another boat in spring of 2004. Overall, shredding measurably affected water quality, but specific effects varied as a function of shredding site and season. Significant increases were observed for total Kjeldahl nitrogen and total phosphorus for all experiments. Dissolved oxygen impacts varied by site, decreasing after shredding at the agricultural slough but increasing at the tidal wetland. The increase in dissolved oxygen likely resulted from tidal incursions from the adjacent river. A year-long time series of dissolved oxygen data indicated a negative relationship between hyacinth abundance and dissolved oxygen concentrations. Hyacinth contained similar tissue concentrations of mercury to underlying sediments, suggesting that plant harvesting could aid mercury remediation efforts. Simple mass calculations indicated that Delta-wide shredding operations could cause between 0.1% and 8.5% increases in the overall abundance of carbon, nitrogen, and phosphorus in the Delta water column. Results suggest that local effects of management actions to control invasive aquatic plants will vary widely as a function of site-specific hydrology, but that Estuary-wide effects would be limited.

Last Modified: 9/10/2014
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