Ecotoxicological impact of Zequanox®, a novel biocide, on selected non-target Irish aquatic species

• Representative non target organisms native to an Irish ecosystem were exposed to Zequanox.
• 72-h static renewal toxicity tests.
• After 72 h, endpoints were reported as LC10, LC50, and LC100.
• Anodonta: ≥500 mg a.i./L; C. plumosus: 1075 mg a.i./L; A. pallipes: ≥750 mg a.i./L.
• No impact to these organisms at concentrations required for >80percent zebra mussel mortality.

Effective, species-specific zebra mussel control is needed urgently for Ireland׳s freshwater bodies, which became infested with non-native zebra mussels in the 1990s. Zequanox®, a newly commercialized product for zebra and quagga mussel control, is composed of dead Pseudomonas fluorescens CL 145A cells. This paper describes ecotoxicology tests on three representative native Irish freshwater species: Anodonta (duck mussel), Chironomus plumosus (non-biting midge), and Austropotamobius pallipes (white-clawed crayfish). The species were exposed to Zequanox in a 72-h static renewal toxicity test at concentrations of 100–750 mg active ingredient per liter (mg a.i./L). Water quality parameters were measured every 12–24 h before and after water and product renewal. After 72 h, endpoints were reported as LC10, LC50, and LC100. The LC50 values derived were (1) Anodonta: ≥500 mg a.i./L (2) C. plumosus: 1075 mg a.i./L, and (3) A. pallipes: ≥750 mg a.i./L. These results demonstrate that Zequanox does not negatively affect these organisms at the concentration required for >80percent zebra mussel mortality (150 mg a.i/L) and the maximum allowable treatment concentration in the United Sates (200 mg a.i./L). They also show the overall species-specificity of Zequanox, and support its use in commercial facilities and open waters.