28.lake.davis.10

28.lake.davis.10 - Rotenone, Northern Pike and Lake Davis...

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Unformatted text preview: Rotenone, Northern Pike and Lake Davis Introduction Rotenone as a Piscicide Rotenone and its Fate Lake Davis in 1997 and 2007 Summary and Conclusions I. Introduction Lake Davis is a major sport fishing area. It is a man-made reservoir with a self-sustaining trout population. The local economy of Portola, CA, depends on tourism. The lake has historically served as the town's water supply. Lake Davis A Temperate Lake! Annual Cycling of Temperate Lakes The Concern Driving the Program Lake Davis was infested with introduced northern pike. Pike decimated the rainbow trout population. The sport fishery was threatened with permanent decline. If they had escaped, pike could have decimated fish populations (trout, salmon, striped bass, and sturgeon) downstream (to SF Bay). The Possible Solution Treat the lake with the piscicide rotenone to eradicate the pike. Other impacted fishes could be restocked later. This was unsuccessfully attempted in 1997. When treated again, there was concern for long term impacts. II. Rotenone as a Piscicide It is a rotenoid isolated from the derris root (pea family). Some 68 species of Leguminosae are known to produce it. Used as a piscicide as early as 1725 in Malaya and South America. It blocks mitochondrial electron transport, thus H O blocking oxidative phosphorylation (ATP production O from NADH). O It is particularly toxic to gill breathing animals. O H O O Rotenone Formulations Applied as dried powder or extract as CFT Legumine, Chem-Fish, Noxfire, Rotacide, Pro-Noxfish, NusynNoxfish, etc. Extracted from dried roots with TCE or other solvents. 24-h LC50: pike = 3 mg/L. 96-h Oral LD50: rats = 132-1,500 mg/kg. III. Rotenone and its Fate An ideal pesticide selectively eradicates the pest. Once done, it then rapidly dissipates. Potential Dissipation Routes for a Chemical in Lake Davis Volatilization Photodegradation Photodegradation Microbial Degradation Chemical Bioconcentration Biodegradation Sediment Adsorption Microbial Degradation Seepage and Leaching Properties of Rotenone to Estimate Fate (at 20-25oC) Water solubility (S) = 0.20 mg/L (low) Vapor pressure (P) = 0.001 Pa (low) -7 3 Air-water partitioning (H) = 1x10 mPa m /mol (low) Organic partitioning (log K ) = 4.2 (moderate) ow Bioconcentration by fishes (BCF) = NA Degradation = oxidation, photolysis, microbial degradation Dissipation of Rotenone in Lake Davis Volatilization Photodegradation Photodegradation Microbial Degradation Chemical Bioconcentration Biodegradation Sediment Adsorption Microbial Degradation Seepage and Leaching Environmental Dissipation Semi-log10 plot provides slope: d Slope = -K / 2.303 50 d DT = 0.693 / K Half life determines chemical persistence. Within 6 half-lives > 98% of a chemical will dissipate. DDT = 4-30 y (temperate soils) Malathion = 24 h (temperate soils); 1-2 w (water) Rotenone = 1-3 d (temperate soils and water) IV. Lake Davis 1997 and 2007 In 1997 the lake was treated with rotenone in late-October. Monitoring for chemicals and pike began immediately. Why was October chosen for the treatment time? (Observed Chemical Dissipation) Rotenone/rotenolone = below detection limits after 7 wk. Piperonyl butoxide = below detection limits after 9 mo. Why did it take so long for rotenone to dissipate? Pike were rediscovered in 1999 why? Lake Davis 1997 Lake Davis 2007 The lake was again treated in 2007 with rotenone in mid-September. Why earlier in the year? Lake Davis 2007 Lake Davis 2007 Lake Davis 2007 Summer Conditions Can Enhance Dissipation Solubility is enhanced by high temperatures ...thus rotenone dispersal and potency are most effective Volatility is enhanced by high temperatures ...thus chemical volatilization is most pronounced Microbial actions are enhanced by high temperatures ...thus microbial degradation is most efficient Photodegradation is enhanced by intense sunlight ...thus degradation via sunlight is most efficient In 2007, rotenone was below detection limits within 2 weeks. V. Summary and Conclusions Lake Davis was infested with predatory northern pike. The threat was to both the local economy and state's environment. Rotenone was chosen due to its proven selectivity and effectiveness. Knowledge of s chemical's properties can provide insight into its fate. In 1997, rotenone's effectiveness and dissipation were negatively impacted by less than optimal environmental conditions. In 2007, the use of optimal environmental conditions enhanced both its effectiveness and rapid dissipation. ...
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28.lake.davis.10 - Rotenone, Northern Pike and Lake Davis...

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