Exposure-related effects of formulated Pseudomonas fluorescens strain CL145A to glochidia from seven unionid mussel species

Abstract

The study was completed to evaluate the exposure-related effects of a biopesticide for dreissenid mussel ( Dreissena polymorpha , zebra mussel and Dreissena rostriformis bugensis , quagga mussel) control on glochidia from unionid mussels endemic to the Great Lakes and Upper Mississippi River Basins. The commercially prepared biopesticide was either a spray-dried powder (SDP) or freeze-dried powder (FDP) formulation of Pseudomonas fluorescens , strain CL145A. Glochidia of the unionid mussel species Lampsilis cardium , Lampsilis siliquoidea , Lampsilis higginsii , Ligumia recta , Obovaria olivaria , and Actinonaias ligamentina were exposed to SDP-formulated P. fluorescens and Lampsilis cardium and Megalonaias nervosa were exposed to FDP-formulated P. fluorescens . All exposures were static, 24 hours in duration, and included six treatment groups. The treatment groups included (1) an untreated control, (2) a positive control which received a nominal target active ingredient (AI) concentration of 300 milligrams per liter (mg/L) of heat-deactivated test article, and (3) treatments that received nominal target AI concentrations of 50, 100, 200, and 300 mg/L of test article. All treatment concentrations are reported based on active ingredient. Glochidia viability was reduced in two of the six species exposed to 50 mg/L SDP and in four of the six species exposed to 100 mg/L SDP when compared to untreated control groups at 6, 12, and 24 hours. Regardless of sample time, concentrations of 200 and 300 mg/L of SDP and 300 mg/L of heat-deactivated SDP (positive control) substantially reduced glochidia viability in all species except, L . higginsii . Glochidia viability was only reduced for L. cardium exposed to FDP at concentrations ≥ 200 mg/L. After 24 hours of FDP exposure, differences in glochidia viability were only detected in M . nervosa that were exposed to 300 mg/L of heat-deactivated SDP. However, given the low viability in the control group, the results for M . nervosa should be interpreted with caution.