Susceptibility of the Non-Targeted Crustacean Eurytemora affinis to the Endocrine Disruptor Tebufenozide: A Transcriptomic Approach

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.

The copepod Eurytemora affinis as a relevant species to assess estuarine sediment toxicity: Effects on gene expression and swimming behavior

Compared to freshwater ecosystems, the health status of estuarine waters remains little studied despite their importance for many species. They represent a zone of interest for Human settlements that make them the final sink of pollution in both the water column and sediment. Once in sediments, pollutants could represent a threat to benthic as well as pelagic estuarine species through resuspension events. In the Seine estuary, the copepod Eurytemora affinis has been previously presented as a relevant species to assess resuspended sediment contamination through fitness-related effects at the individual level. The aim of the present study was to use E. affinis copepods to assess estuarine sediment-derived elutriates toxicity at environmental concentrations of particles using a molecular (i.e. transcriptomics) and a behavioral approach. Two sites along the Seine estuary were sampled. The analysis of sediments reveals that both sites have the same granulometric composition and close contamination profiles with the detection of PCBs, PAHs and pyrethroid insecticides. The transcriptomic analysis reveals that exposure to elutriates from both sites triggers the dysregulation of genes involved in biological function as defense response, immunity, ecdysone pathway or neurotoxicity with 66% and 36% of shared genes at the highest concentration for Tancarville and Fatouville. This analysis also reveals a higher count of dysregulated genes in the Fatouville site compared to the Tancarville (271 vs 148) despite their close contamination profile. These results emphasize the molecular approach sensitivity to assess environmental matrix toxicity with E. affinis. The analysis of the swimming behavior of E. affinis did not highlight significant effects after elutriate exposure. However, our strategy to assess E. affinis swimming behavior allows the discrimination of basal swimming behavior i.e. dark/light velocity changes and strong thigmotaxis behavior. Thus, it represents a promising standardized tool to assess copepods swimming behavior in ecotoxicological studies.

Responses of the copepod Eurytemora affinis to trace metal exposure: A candidate for sentinel to marine sediment resuspension effects

Our study reports the ability of Eurytemora affinis to indicate certain responses in 96 h when exposed to resuspended sediment from a polluted site (PS, Seine estuary, France), less polluted site (LPS, Canche estuary, France) and dissolved trace metals. Mortality from dissolved trace metal was highest (57.5 %) followed by PS (38.59 %) > LPS (24.04 %). The exposure to PS sediment resulted in significantly lower no. of early larval stage (nauplii < 2), sex-ratio (39.24 % of males) and higher ovigerous female (>10). Eurytemora affinis bioaccumulated high concentrations of copper (27.3 mg/kg), nickel (12.8 mg/kg), lead (21.8 mg/kg) and arsenic (13.7 mg/kg) from PS exposure with significantly lower bioaccumulation of metals from LPS. The bioconcentration factor (BCF) was highest from dissolved toxicity (>2000) followed by PS that showed significantly higher BCF for Nickel and Copper, compared to LPS. The responses of E. affinis to different matrices exemplify its role as a sentinel.