Benz[a]anthracene (BaA) is a ubiquitous polycyclic aromatic hydrocarbon found in numerous aquatic ecosystems. However, ecotoxicological data in aquatic organisms are scarce. To remedy this lack of data, Japanese medaka (Oryzias latipes) embryos were exposed to BaA and toxic effects were investigated at multiple toxicological endpoints. Japanese medaka embryos were incubated onto BaA-spiked artificial sediment for 9 days at low or moderate environmental concentrations ranging from 0.9 to 12 µgg(-1) dw. BaA-exposed embryos exhibited significant tachycardia. BaA exposure was also shown to increase CYP1A activity in the hepato-biliary tissue as well as craniofacial deformities and DNA damage in pro-larvae. The photomotor response of BaA-exposed larvae was reduced in comparison to the control group. According to this set of tests, the lowest tested and observed effect concentration (LOEC) for Japanese medaka early life stages was equivalent to 0.92 µgg(-1) dw of BaA. This concentration fall into the range of concentrations frequently encountered in sediments of polluted aquatic ecosystems. Taking into consideration these results, BaA represents a threat for fish early life stages in particular those developing onto or into contaminated sediments.

Uranium (U) toxicity patterns for fish have been mainly determined under laboratory‐controlled waterborne exposure conditions. Because fish can take up metals from water and diet under in situ exposure conditions, a waterborne U exposure experiment (20 μg L−1, 20 d) was conducted in the laboratory to investigate transfer efficiency and target organ distribution in zebrafish Danio rerio compared with combined waterborne exposure (20 μg L−1) and diet‐borne exposure (10.7 μg g−1). 233Uranium was used as a specific U isotope tracer for diet‐borne exposure. Bioaccumulation was examined in the gills, liver, kidneys, intestine, and gonads of D. rerio. Concentrations in the organs after waterborne exposure were approximately 500 ng g−1 fresh weight, except in the intestine (> 10 μg g−1 fresh wt) and the kidneys (200 ng g−1 fresh wt). No significant difference was observed between waterborne and diet‐borne conditions. Trophic U transfer in organs was found but at a low level (< 10 ng g−1 fresh wt). Surprisingly, the intestine appeared to be the main target organ after both tested exposure modalities. The gonads (57% at 20 d) and the liver (41% at 20 d) showed the highest accumulated relative U burdens. Environ Toxicol Chem 2019;38:90–98. © 2018 SETAC