Comparative study of the effects of salinity on life-cycle parameters of four soil-dwelling species ( Folsomia candida, Enchytraeus doerjesi, Eisenia fetida and Aporrectodea caliginosa)

We studied the effect of salinity on some life-cycle parameters in the collembolan Folsomia candida, the enchytraeid Enchytraeus doerjesi, and two earthworm species, Eisenia fetida and Aporrectodea caliginosa, using natural saline soil from Robertson, Western Cape, South Africa. Specimens of the four species were exposed to soils along a gradient of salinity with electrical conductivity (EC) ranging from 0.08 to 1.62 dS m −1, under controlled laboratory conditions for 28 days. The results showed that although survival of E. doerjesi and F. candida was not significantly affected in this salinity range, juvenile production was significantly affected at 1.03 dS m −1 and higher. For E. doerjesi, absolute cessation of reproduction occurred at 1.31 dS m −1 while for F. candida, it occurred at a higher EC of 1.62 dS m −1. For E. fetida and A. caliginosa, survival was significantly affected at and above 0.92 and 1.31 dS m −1, respectively, while total mortality occurred at 1.31 and 1.62 dS m −1, respectively. Both earthworm species only produced cocoons in control soils. Growth of A. caliginosa was significantly affected at a lower EC (0.52 dS m −1) than that which affected the growth of E. fetida (1.03 dS m −1). Thus, the sensitivity of these soil organisms to saline stress, based on survival and reproduction data increased in the order: F. candida< E. doerjesi< A. caliginosa< E. fetida. Further investigation and of more taxa, may support the findings of this study that suggest that earthworms could be useful as indicators of saline disturbance than other taxa.