Comparison of the sensitivity to heavy metals and pentachlorophenol of the mayflies Deleatidium spp. and the cladoceran Daphnia magna

Abstract

A laboratory testing protocol has been established for the mayfly Deleatidium spp. This involves incubation of organisms for 96 h at 15°C with continuous aeration. Under these conditions EC50 concentrations for Deleatidium were similar to those for the cladoceran Daphnia magna (48 h test) for four heavy metal toxicants (Cd²⁺, Cr⁶⁺, Cu²⁺, and Zn²⁺ ) and one organic compound (pentachlorophenol). The EC₅₀ concentration for Zn²⁺ was, however, markedly higher for Deleatidium, indicating lower sensitivity. Deleatidium showed a strong increase in sensitivity with increasing exposure time, suggesting that the organism may be relatively insensitive to short‐term (< 24 h) elevations in heavy‐metal concentrations. Comparison with published data for other riverine invertebrates and fish suggests that Deleatidium is among the more sensitive species.

Keywords:

• Deleatidium
• mayflies
• heavy metals
• cladocerans
• toxicity
• water quality