Development of a larval bioassay using the calanoid copepod, Eurytemora affinis to assess the toxicity of sediment-bound pollutants

•A new copepod larval assay which enables the assessment of particle-bound pollutants.•A relatively rapid and sensitive test covering the most sensitive stage of E. affinis.•E. affins relatively sensitive to AP, PAHs and PCBs released from particles.•Growth, leading to naupliar body length being considered as a more sensitive endpoint than survival.•This work constitutes the essential validation step before assessment of the toxicity of natural sediments.

Hydrophobic pollutants, in particular sediment-sorbed organic compounds, are widespread in the aquatic environment and could represent a threat to living organisms. Estuarine species, which live in turbulent ecosystems, are particularly exposed to this mode of contamination. For precise evaluation of the toxicity of hydrophobic contaminants desorbed from particles, a new larval assay using nauplii of the estuarine calanoid copepod Eurytemora affinis was developed. It consists of the direct exposure of copepods during naupliar development to elutriates of an unpolluted sediment spiked with different model contaminants. This bioassay measures the toxicity of the bioavailable fraction of particle-sorbed pollutants on the naupliar stage of copepods. Mortality and growth (non-invasive endpoints) in nauplii were analysed after six days of exposure. This approach was validated using six pollutants with different modes of action: benzo[a]pyrene (BaP), dimethylbenzo[a]anthracene (DMBA), phenanthrene (PHE), polychlorinated biphenyls (PCB 126, PCB 153) and 4-nonylphenol (4-NP). All these compounds induced a dose-dependent increase in toxic effects. Lethal effects only occurred at the highest tested concentrations: 58,541 and 6092 ng g−1 dry weight sediment (dws), for PHE and DMBA, respectively. Sublethal effects (growth inhibition) were observed at lower concentrations for all tested compounds except PCB 153, from 8, 142, 297, 6092 and 8453 ng g−1 dws for PCB 126, BaP, PHE, DMBA and 4-NP, respectively.