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Upper Midwest Environmental Sciences Center

Evaluation of CO2 as a dreissenid mussel control tool

Supervisor - James Luoma
Principal Investigator
– Diane Waller


Dreissenid mussels, (zebra mussel, Dreissena polymorpha and quagga, D. rostiformis bugensis) continue to expand their range across the United States and into Canada (USGS 2015) causing significant ecological and economic impact where they have established (Nalepa and Schloesser 2014).  The estimated economic costs of zebra mussels to U.S. and Canadian water users in the Great Lakes region was $5 billion (USGS 2011) from 2000-2010. Chemical control has been the most common method to manage zebra mussels in closed water systems (Mackie and Claudi 2009, Claudi and Mackie 1994). The available arsenal of molluscicides includes sodium hypochlorite, salts, copper compounds and quaternary ammoniums (Glomski 2015). More recently, the biopesticide Zequanox® (Marrone BioInnovations, Davis, CA) was approved for use in open water to control dreissenid mussels. The active ingredient of the product is killed cells of the common soil bacterium, Pseudomonas fluorescens, strain CL145A Molloy et al. 2013a); it has shown selectivity to dreissenids and safety to a range of nontarget organisms (Molloy et. al. 2013b, Molloy et al. 2013c, Meehan et al. 2014, Luoma et al. 2015a and 2015b, Weber 2015). However, Zequanox can be costly and impractical for application in large static systems; additionally, it is most effective at water temperatures >14°C (MBI 2012). There is a need for development of alternate control tools that are applicable in open and closed water systems and are effective in cold water. Scheduling control efforts for dreissenids in the late fall or winter may minimize impact to nontarget organisms, such as unionid mussels and larval fish, which are buried or less abundant at that time.
Carbon dioxide has been tested as a control tool for several species of invasive molluscs including the zebra mussel, the Asian clam (Corbicula fluminea) (McMahon et al. 1995; Elzinga and Butzlaff 1994), and New Zealand mud snail (Potamopyrgus antipodarum) (Nielson et al. 2012). Elzinga and Butzlaff (1994) reported that Asian clams were narcotized at 100 mg/L CO2 and were killed at 500 mg/L CO2. In the same study, adult zebra mussels were narcotized at levels from 50-253 mg/L CO2 in < 6 h (Elzinga and Butzlaff 1994). The LC5O values reported for zebra mussels at 48 h and 96 h were 196 and 74 mg/L (18°C) and 290 and 81 mg/L (22°C), respectively. McMahon et al. (1995) reported that a gas mixture with 5% CO2 caused no mortality in zebra mussels, but induced narcotization and byssal thread detachment. A 10% CO2 gas mixture produced 100% mortality of zebra mussels within about 1 week of exposure.

Carbon dioxide causes similar effects in native unionid mussels. The LC50 value for fat mucket (L. siliquoidea) juvenile mussels at 28 d was 76 mg/L (22°C) (Waller, unpublished data). Although the LC50 values were similar, the shorter exposure duration (96 h) in McMahon et al. (1995) suggests that zebra mussels may be more sensitive to CO2 than the native mussel. In the same study, fat mucket mussels were narcotized at levels from 110-260 mg/L in <12 h, but byssal thread production was not measured (Waller, unpublished data). The structure and function of the byssal thread varies between dreissenid and unionid mussels. The byssal organ of dreissenids resembles that of marine mytilid mussels, producing numerous threads and an adhesion plaque to hold the mussel in place. In contrast, the byssus of a unionid mussel consists of a single hyaline thread, produced primarily during the juvenile stage (Howard 1922).  Little is known about the structure, ultrastructure, and function of the byssal thread in unionids. The byssus of unionid mussels is primarily used by the juvenile for attachment to the substrate and for drift, but adults of some species also form a byssus (Bradley 2011). Potential differences in the effect of CO2 on byssal thread formation between dreissenids and unionids could be exploited to selectively target the invasive mussel.

Results of previous studies suggest that carbon dioxide alone or in combination with other treatments has potential for use as molluscicide. Additional information is needed on the toxicity of carbon dioxide at colder water temperatures and the sublethal effects (i.e., byssal thread formation and narcotization) of exposure on zebra mussels and native unionid mussels.


  1. Determine the toxicity of carbon dioxide to zebra mussels in 48 h and 96 h exposures at 12°C.
  2. Compare toxicity, behavioral (i.e., narcotization) and byssus responses to carbon dioxide exposure between zebra mussels and fat mucket juveniles.


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Molloy DP, Mayer DA, Giamberini L, Gaylo MJ (2013b) Mode of action of Pseudomonas fluorescens strain CL145A, a lethal control agent of dreissenid mussels (Bivalvia: Dreissenidae). Journal of Invertebrate Pathology 113: 115-121

Molloy DP, Mayer DA, Gaylo MJ, Burlakova LE, Karatayev AY, Presti KT, Sawyko PM, Morse JT, Paul EA (2013c) Non-target trials with Pseudomonas fluorescens strain CL145A, a lethal control agent of dreissenid mussels (Bivalvia: Dreissenidae). Management of Biological Invasions 4: 71–79

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