What is a Nonoxidizing Molluscicide? A molluscicide which does not act as a chemical oxidant

1. Nonoxidizing Biocides,Thermal Shocking,Desiccation, Oxygen Deprivation, Carbon Dioxide and Low Frequency Agitation Robert F. McMahon Department of Biology The University of Texas at Arlington Arlington, Texas 76019

2. What is a Nonoxidizing Molluscicide? • A molluscicide which does not act as a chemical oxidant • Does not induce corrosion of metallic surfaces • Organic or metallic molluscicides • Typical oxidizing molluscicides • Chlorine, Sodium Hypochlorite • Chlorine dioxide • Chloramine • Bromine • Bromine, Bromine/Chlorine • Ozone • Potassium Permanganate, • Hydrogen peroxide

3. COMMERCIAL NONOXIDIZING MOLLUSCICIDES Poly[oxyethlene(dimethyliminio)ethylene (dimethylimino)ethylene dichloride] Bulab 6002 (Buckman Laboratories) 0.5 ppm for 826 h - 100% Adult Mortality 2 ppm for 313 h - 100% Adult Mortality 8 ppm for 197 h - 100% Adult Mortality 2-(Thiocyanomethythio)benzothiazole Bulab 6002 (Buckman Laboratories) 0.5 ppm for 758 h - 100% Adult Mortality 2 ppm for 313 h - 100% Adult Mortality 4 ppm for 260 h - 100% Adult Mortality Didecyl dimethyl ammonium chloride H-130 (Calgon) 1 ppm for 24 h - 100% Adult Mortality N-alkyl dimethyl benzyl ammonium chloride &Dodecylguanidine hydrochloride Clam-trol - 1 or CT-1 (Betz Industrial) 15 ppm for 12 h at 11°C - 100% Adult Mortality after 48 h 15 ppm for 14 h at 14°C - 100% Adult Mortality after 48 h 15 ppm for 6 h at 20°C - 100% Adult Mortality after 24 h 15 ppm for 14 h at 20°C - 100% Adult Mortality after 48 h

4. N-alkyl dimethyl benzyl ammonium chloride Clam-trol-2 or CT-2 (Betz Industrial) 2-5 ppm applied for 6-24 h - 100% Adult Mortality N-alkyl dimethyl benzyl ammonium chloride Clam-trol - 4 or CT-4 (Betz Industrial) 13 ppm for 72 h at 5° or 10°C - >90% Adult Mortality 13 ppm for 48 h at 15°C - 100% Adult Mortality 13 ppm for 12 h at 20°C - 90% Adult Mortality Akyldimethylbenzyl ammonium chloride & Akyldimethylethylbenzyl ammonium chloride Mactrol 9210 (Nalco) 0.5 ppm for 249 h at 18°C - 100% Adult Mortality 0.5 ppm for 120 h at 22°C - 100% Adult Mortality 2.0 ppm for 65 h at 18°C - 100% Adult Mortality 2.0 ppm for 45 h at 22°C - 100% Adult Mortality Compound with Primary and Secondary Aminated Carbon Chains Mexel 432 (Mexel) 2 ppm for 1.5h/day for 30 days - 40% Adult Mortality 10 ppm for 1.5 h/day for 30 days - 62-77% Adult Mortality Dichloro-2'nitro-4' salicylanilide Bayluscide (Bayer) 0.05 ppm for 24 h - 70% Adult Mortality 0.1 ppm for 24 h - 100% Adult Mortality

5. N-triphenylmethyl-morpholine Frescon (Shell) 0.5 ppm for 24 h - 70% Adult Mortality 0.9 ppm for 24 h - 100% Adult Mortality Benzalkonium chloride (Fish Culture Disinfectant) 10 ppm for 20 min - 43% Veliger Mortality after 24 h 100 ppm for 20 min - 80% Veliger Mortality after 24 h 1000 ppm for 20 min - 100% Veliger Mortality after 24 h Tert-butyhydroxyquinone in paints TBHQ Can reduce but not eliminate settlement Butylated Hydroxytoluene in paints BHT Can reduce but not eliminate settlement Surfactant Agent TD-2335 (Elf Atochem North America) 1-1.5 ppm for 6-8 h - 100% Adult Mortality 48 hr LC50 = 0.48 ppm (juveniles), 0.59 ppm (adults)

6. 1,1'-(Methyliminio)bis(3-chloro-2-propanol), polymer with N,N, N',N'-tetramethyl-1,2-ethanediamine Bulab 5001 (Buckman Laboratories) 3 ppm for 1295 h at 20°C - 100% Juvenile Mortality 9 ppm for 346 h at 20°C - 100% Juvenile Mortality 3 ppm for 1295 h at 20°C - 100% Adult Mortality 9 ppm for 633 h at 20°C - 100% Adult Mortality Petroleum Jelly, Lanolin, Zinc oxide, Talc, Petroleum distillates (Major ingredients), Panthenol, Sorbitan sesquioleate, cetylridinium chloride, Allantoin, Witch Hazel (Minor ingredients) Penaten-Creme (Johnson and Johnson Co.) Diaper ointment used in Europe as an antifoulant compound. Inhibits adult mussel byssal re-attachment and pediveliger initial attachment Aluminum sulfate (Alum) Al (SO ) Copper sulfate in Solution CuSO 100 ppm for 5 h at 22.5°C - 40% Adult Mortality 300 ppm for 5 h at 22.5°C - 55% Adult Mortality

7. Tri-butyl tin oxide Applied in Surface Coatings Every 1-2 Years Inhibits Settlement (Not generally permitable) Zinc Hot Metal Spray, in Paints or Galvanization Inhibits Settlement Copper Hot Metal Spray, in Paints or Galvanization Inhibits Settlement Ions in solution (cathodic release) 5 ppm for 24 h - 100% adult kill Potassium ion in solution As 160-640 ppm KH PO - 100% Veliger Mortality As 10 ppm KOH - 100% Veliger Mortality As 50 ppm KCl - 100% Adult Mortality

8. NONCOMMERCIAL NONOXIDIZING MOLLUSCICIDES Saponin Compounds Extracted from the Berries of the African Soapberry Plant Endod 15 ppm continuously applied - 100% Adult Mortality Alkaloid Extract of Capsaicin Pepper Plants Capsaicin 20.1±1.10 µM continuous - 90% inhibition of byssal attachment without mortality N-vanillylnonanamide 25.4±5.3 µM for 48h - 90% inhibition of byssal attachment without mortality N-benzoylmonethanolamine benzoate 58.4±4.6 µM for 48 h - 90% inhibition of byssal attachment without mortality (+)-Butanedioic acid, Mono[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl]ester 50 ppt for 48h – Inhibits byssal attachment (+-)-3,4-Dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid 50 ppt for 48h – Inhibits byssal attachment (Poly-N-acetyl--D-glucosamine)-protein 100 ppt for 48 h – 100% adult mortality

9. Marine Extracts of Macrophytic Algae (Fucus and Ulva) In coatings (Experimental) Inhibits pediveliger settlement and adult byssogenesis

10. Comparison of Nonoxidizing and Oxidizing Molluscicides • ADVANTAGES of NONOXIDIZING MOLLUSCICIDES • Fewer precautions required for on-site storage • Fewer safety hazards in handling and use • May have greater toxicity than oxidizing agents • Do not generally induce valve closure • Surfactant agents may be less toxic to nontarget organisms than oxidizing molluscicides • Due extensive surface area of living epithelial tissue in bivalves • Application technology and hardware is often inexpensive and readily installed • Readily and simply deactivated in effluents • Generally noncorrosive to metal, silicone and rubber based seals • Do not produce carcinogenic by-products (THMs)

11. Nonoxidizing Molluscicide Application Strategies • Periodic Mitigation • Continuous Application • Intermittent Application • Semicontinuous Application

12. Periodic Application • Short-term molluscicide addition at elevated concentrations mitigating established populations • Applied at a frequency preventing system degradation (1-3 times annually) • Adjusted to local population reproductive cycles • Advantages: • Low annual cost and molluscicide usage • Disadvantages: • Requires extensive and continuous monitoring • Allows mussel fouling to become established • May release shells and bodies into system • High application levels may require discharge detoxification

13. Continuous Application • Continuous application at low concentrations • Prevent pediveliger settlement • Prevent survival of translocating juvenile mussels • Advantages: • Prevents establishment of mussel fouling • Application technology is relatively simple • Discharge molluscicide concentrations are low, but continuous • Reduces microbially influenced corrosion (MIC) • Extensive mussel monitoring is not required • Disadvantages: • Relatively high annual use of molluscicide • Relatively high costs • High annual release of molluscicide

14. Intermittent Application • Daily, bidaily, or tridaily at intermediate concentrations for 0.5 to 3 hours per addition • Prevents pediveliger settlement • Advantages: • Slows establishment of mussel fouling • Discharge of molluscicide reduced compared to continuous application • Reduces costs • Reduces microbially influenced corrosion (MIC) • Can be limited to mussel spawning periods • Disadvantages: • Cannot mitigate pre-established fouling • Will not generally prevent fouling by translocating juvenile and adult mussels • Must monitor juvenile and adult settlement

15. Semi-continuous Application • Rapid, on-off cycling of molluscicide addition at low concentrations as used in continuous application • On 15-30 min followed by off periods of 15-90 min • Applied at low concentrations as in continuous application • Advantages: • Prevents establishment of mussel fouling • Discharge of molluscicide reduced compared to continuous application, reducing costs • Reduces microbially influenced corrosion (MIC) • Will mitigate pre-established mussel fouling • Disadvantages: • Involves larger annual use of molluscicide than in periodic or intermittent application • Application technology may be complex

16. Conclusions • Nonoxidizing molluscicides offer a viable alternative to oxidizing molluscicides for zebra mussel fouling • Wide variety of nonoxidizing molluscicides available • Are highly effective against zebra mussels and some are relatively benign to nontarget species compared to oxidizing molluscides • Application technology and storage are simple • Costs can be competitive with oxidizing biocides • Can reduce microbially influenced corrosion (MIC) • Readily applied to low volume facilities and systems • Choice of agent and application technology can be customized to facility requirements and limitations on a site-by-site basis

17. Thermal Control Strategies • Zebra mussels are northern temperate species • Results in having reduced tolerance of elevated temperatures • Can tolerate 0°C throughout the winter • Do not tolerate prolonged exposure to 30°C • Incipient upper thermal limit • Low upper lethal limits make zebra mussels susceptible to thermal mitigation/control technologies • Two basic thermal treatment technologies • Chronic thermal treatment • Acute thermal treatment

18. ACUTE THERMAL TOLERANCE • Tolerated temperature in response to rapidly increasing temperature or instantaneous exposure to a lethal temperature • Affected by of rate of temperature increase and prior temperature experience • CHRONIC THERMAL TOLERANCE • Tolerance time when continuously exposed to lethal temperatures • Affected by exposure temperature and prior temperature experience

35. Carbon Dioxide Treatment • Carbon dioxide is a weak acid • CO2 + H2O → H2CO3 → H+ + HCO3- → 2 H+ + CO32- • Bivalves do not have pH buffering blood proteins • Increased CO2 concentration in medium increases CO2 concentration in blood lowering its pH • Slight reductions in blood pH induce stress and mortality so that CO2 could act as a molluscicide • Inexpensive, readily stored on site, easily applied, highly biodegradable • Utilized by aquatic plants, algae and bacteria

36. Methods: Carbon Dioxide Tolerance • Treatment temperature = 25°C • Mussels exposed to 5% and 10% CO2 • Pco2 = 38 and 76 Torr, respectively • Tolerance times determined • Mussels allowed to byssally attach to clear plastic plates over the course of the exposures • Number of new byssal attachment produced determined daily

39. Low Frequency Agitation • Low frequency agitation (20-60 cps) can inhibit production of byssal threads and induce byssal release in zebra mussels • May be the reason that adult mussels are not found in shallow waters agitated by wave action • Could be used as a nonchemical method for controlling or mitigating fouling • Low frequency agitators in embayments • Flutter valves in water lines or intake tunnels • Bubble Sreens, Bubbler Systems • Higher frequency sound has not proven successful

40. Methods: Low Frequency Agitation • Mussels allowed to attach to plastic plates • Water agitated back and forth past the plates • 0, 10, 20, 30, and 40 cycles/min (cpm) • Number of byssal threads produced counted daily • Number of mussels sontaneously releasing from byssus observed

42. Use of Bubble Screens and Plates for Mitigation of Zebra Mussel Macrofouling

43. Conclusions • Thermal treatments successfully mitigate and control dreissenid macrofouling • Acute and chronic treatments • Anoxia/hypoxia could be efficacious for mitigation of zebra mussel infestations • Best applied during warmer months • Will require reducing oxygen concentrations to less than 15% of full air oxygen staturation • Drawing from deoxygenated hypolimnetic waters • Desiccation has been successfully used to control mussel macrofouling • Draw-down during warm summer or freezing winter periods • Dewatering components • Forced warm air • Carbon dioxide injection could an efficacious mitigant • 10% will kill mussels, 5% stimulates release from byssus • Low frequency agitation could be an effective mitigant • > 50 cpm causes 100% byssal release • < 40 cpm inhibits production of byssal threads • Flutter valves, agitators or bubble screens could prevent settlement