Niphargus and Gammarus from karst waters: first data on heavy metal (Cd, Cu, Zn) exposure in a biospeleology laboratory

Niphargus montellianus and Gammarus balcanicus, hypogean and epigean amphipods, respectively, living in karst waters of North-Eastern Italy, were exposed in a biospeleology laboratory to three heavy metals (Cd, Cu, Zn). Metal contents were checked in organisms in natural conditions and after exposure to increasing concentrations of metals in the range 0.1-25.0 μg ml-1 for up to 10 days. The two amphipods differed in their responses, the epigean G. balcanicus being more sensitive to the toxic effects of heavy metals than the hypogean N. montellianus. The degree of toxicity was Cu>Cd>Zn for both amphipods; in particular, Cu induces 50% mortality for G. balcanicus in 2 days at the concentration of 0.1 μg Cu ml-1 and at the concentration of 5 μg Cu ml-1 in 10 days for N. montellianus, respectively. Moreover, G. balcanicus accumulated higher levels of Cd and Zn than N. montellianus, and its mortality was always higher. The suitability of the two species as biomonitors of karst water quality is discussed.