Ecotoxic effect of a soil-stabilizing root-bacterial exopolysaccharide salt on the reproduction of <i>Procambarus clarkii</i> Girard, 1852 (Decapoda: Astacidea: Cambaridae)

Abstract The exopolysaccharide (EPS) produced by Rhizobium tropici ATCC 49672® has been modified to create a stable salt solution and applied as a soil amendment to reduce erosion. We assessed the ecotoxicity of R. tropici-produced EPS on Procambarus clarkii (Girard 1852), the red swamp crayfish. Artificial maternal burrowing chambers were used to monitor behavioral responses to biopolymers in the soil and to observe possible effects on oviposition and hatch rates. The study consisted of post-mated mature females held individually in burrowing chambers containing either control soil or soil amended with 1% EPS. For each treatment, five artificial burrows were placed within each of six bins (n = 3 per treatment) and maintained for 4 mo. The EPS treatment resulted in complete reproductive inhibition, with no oviposition in any of the treated bin chambers compared to 47% ± 23% (mean ± SD) of crayfish producing eggs in the control bin chambers. Control crayfish produced a total of 1,519 hatchlings compared to no hatchlings by crayfish exposed to EPS. Given the potential for soil stabilizers to control P. clarkii populations, a biopolymer salt derived from R. tropici represents a promising management tool that combines ecological benefits with the control of invasive crayfishes.