Physiochemical conditions of Folsomia candida occurrence in a shallow coastal Lake Michigan aquifer

An insect, Folsomia candida, was found in a shallow aquifer along the southwestern coast of Michigan. F. candida is a standard organism for soil toxicity testing but its occurrence in groundwater is uncommon to rare, or has been under-reported in the literature. Attempts to correlate the presence of F. candida to water and soil parameters yielded: (1) F. candida is present in the upper 15–25 cm of topsoil, but absent in the underlying vadose zone except directly above the water table, regardless of the presence in groundwater; (2) F. candida is most abundant in groundwater 4.3–5.0 m below land surface; (3) Most F. candida occur in wells with dissolved oxygen ranging from 4 to 5 ppm; (4) F. candida is most abundant in water between about 14 and 18°C; (5) F. candida is abundant in groundwater with high concentrations of Cl⁻, Na⁺, and K⁺; and, (6) Small differences in pore space volume determine the feasibility of F. candida occupancy, but not the presence of F. candida in the study area.