Zequanox^TM Ecological Testing

Non-Target Aquatic Organism Studies with Zequanox
(killed Pseudomonas fluorescens CL145A)

Ecotoxicology trials have been very encouraging regarding nontarget impact to aquatic organisms.  All evidence indicates that the Pseudomonas fluorescens cellular byproduct that kills Dreissena mussels is not harmful to other aquatic organisms.  Compared to experimental (untreated) controls, little to no mortality has been recorded among the following nontarget organisms when treated at dosages that produced high Dreissena mortality (76–100%):

• Ciliates:  Trials with the common freshwater ciliate Colpidium colpoda indicated that the bacteria were not only nonlethal, but served as a food source permitting higher rates of ciliate reproduction than ciliates held in untreated stream water.
• Freshwater shrimp:  The amphipod Hyalella azteca appears to be mildly sensitive to treatments with Pseudomonas fluorescens strain CL145A (MOI 401), but it appears that most, if not all, of the sensitivity can be attributed to the presence of the particulate bacterial cell matter itself rather than the bacterium’s mussel-killing cellular byproduct.
• Daphnids:  The microcrustacean Daphnia magna is an aquatic filter feeder that ingests small suspended particles including bacteria, making it a highly appropriate organism for nontarget tests.  Laboratory assays indicate that P. fluorescens is nonlethal to this species.
• Fish:  No mortality from killed Pf CL145A has been observed in the following three fish species tested:  fathead minnows(Pimephales promelas), young-of-the-year brown trout (Salmo trutta), and juvenile bluegill sunfish (Lepomis macrochirus).  Trials have indicated that fish can not tolerate exposure to high levels of live bacteria.  Fish trials conducted with dead bacteria, however, have indicated that applications of killed cells were harmless to fish, but were still highly lethal to the Dreissena mussels.  To protect fish, as well as to reduce overall environmental concerns, commercial products based on this microbe will contain almost exclusively dead cells.
• Birds:  No mortality was observed after feeding mallards a 2,000 mg/kg dose of P. fluorescens.  The NOEL was set at >2,000 mg/kg and classified Zequanox as “practically non-toxic to mallard.
• Bivalves:  It is reasonable to think that other bivalve species might be susceptible to P. fluorescens.  Bacterial exposures, however, have caused no mortality to blue mussels (Mytilus edulis) or any of 6 native North American unionid clam species (Pyganodon grandis, Lasmigona compressa, Strophitus undulatus, Lampsilis radiata, Pyganodon cataracta, and Elliptio complanata).

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