Effects of copper and cadmium, isolated and combined, in the survival and behavior of Eurytemora affinis (Copepoda)

The excess of metals released in the environment is of significant concern, and assessing metallic mixtures can be tricky. Copepods are an important link between the producers and higher trophic levels, and their use in ecotoxicology is still scarce compared to other organisms from zooplankton. We evaluated the effects of copper (Cu) and cadmium (Cd), isolated and combined, on nauplii and adults of euryhaline Calanoida copepod Eurytemora affinis from the Seine estuary. The effects of the mixtures were modeled with MixTox, using mortality as endpoint, and the behavior of the adults was evaluated using DanioVision. The nauplii were more sensitive to the metals than adults, especially when exposed to Cd. Regarding the mixtures, the best model to explain the interactions in both stages was the independent action, with synergism in nauplii and antagonism in adults. Synergism was observed in all metallic mixtures to nauplii, increasing with the increase of metals while antagonism was observed in all combinations in adults but with no clear pattern of response related to the metal concentration. Our data suggest that Cd contributed to Cu toxicity in nauplii, but this was not observed in adults. Overall, the copepod's velocity was not significantly affected by the contaminants at the concentrations evaluated. Our data underline the importance of considering (i) the effect of metallic mixtures (ii) in different stages of copepods.