Acute and chronic toxicity of nickel to larvae of chironomus riparis (Meigen)

The acute toxicity of nickel to first and second instars of Chironomus riparis was determined using larvae from a laboratory culture. First instar larvae were found to be significantly more sensitive to nickel than second instars with 48h LC₅₀ values of $\text{79·5 ± 3·7}\text{mg litre}{}^{\mathrm{-1}}$ Ni and 169 ± 10 mg litre⁻¹, respectively.

Longer term chronic toxicity tests (30 days), in which larvae were allowed to develop from eggs until just prior to pupation, indicated that nickel concentrations of up to 25 mg litre⁻¹ appeared to have little effect on the percentage hatch of C. riparis. The growth of larvae was, however, significantly reduced at the lowest nickel concentration (2·5 mg litre⁻¹) tested compared with control larvae. A maximum acceptable toxic concentration (MATC) for the effect of nickel on growth was estimated to be 1·1 mg litre⁻¹ Ni. This value is substantially lower than the LC₅₀ value calculated for first instar larvae and indicates the importance of conducting longer term toxicity tests when assessing the pollution tolerance of an organism.