Multigenerational effects of 4-methylbenzylidene camphor (4-MBC) on the survival, development and reproduction of the marine copepod Tigriopus japonicus.

One of the most widely used organic UV filters, 4-methylbenzylidene camphor (4-MBC), is present at high concentrations in offshore waters. The marine copepod Tigriopus japonicus was exposed to different concentrations of 4-MBC (i.e., 0, 0.5, 1, 5 and 10µgL-1) for 4 consecutive generations (F0-F3) to evaluate the impact of 4-MBC on marine ecosystems. The results showed that in the F0 generation, 4-MBC caused significant lethal toxicity in T. japonicas at concentrations of 5 and 10µgL-1 and the nauplii were more sensitive to 4-MBC toxicity than the adults. However in the F1-F3 generations, 4-MBC exposure did not affect the survival rate. The hatching rate and the developmental duration from the nauplii to the copepodite (N-C) and from the nauplii to adult (N-A) decreased significantly in the F1-F2 generations and in the F2-F3 generations, respectively, even at the lowest exposure concentration (0.5µgL-1). In the subsequent two generations (i.e., the F4-F5 generations) of recovery exposure in clean seawater, the growth rates of the original 4-MBC exposure groups were still faster than the control in both the N-C and N-A stages, suggesting possible transgenerational genetic and/or epigenetic changes upon chronic 4-MBC exposure. The expression of the ecdysone receptor gene was up-regulated by 4-MBC, which was consistent with the decrease of the N-C/N-A duration. In addition, 4-MBC may induce oxidative stress and trigger apoptosis in T. japonicas, resulting in developmental, reproductive and even lethal toxicity. A preliminary risk assessment suggested that under environmentally realistic concentrations, 4-MBC had significant potential to pose a threat to marine crustaceans and marine ecosystems.

Toxicity and bioaccumulation of three hexabromocyclododecane diastereoisomers in the marine copepod Tigriopus japonicas.

The three major hexabromocyclododecane (HBCD) diastereoisomers, i.e. α-, ß- and γ-HBCD, have distinct physical and chemical properties that may potentially result in different levels of bioaccumulation and toxicity in aquatic organisms. To assess the impact of diastereomeric variation in HBCDs, the marine copepod Tigriopus japonicus was exposed to α-, ß- and γ-HBCD in isolation. Results showed that all the three diastereoisomers had a similar potency to cause growth delay in T. japonicas. Variation was observed in the overall survival rate with exposure to α- and ß-HBCD, and this resulted in significantly higher lethal toxicity in T. japonicas than that with exposure to γ-HBCD. Exposure to α-, ß- and γ-HBCD led to the generation of ROS in T. japonicas, a possibly toxic mechanism. Both α- and ß-HBCD showed a higher potential to induce oxidative stress, which may be a factor in the higher lethal toxicity observed with α- and ß-HBCD exposure. It is of note that T. japonicus was found to be more sensitive to all three diastereoisomers in the F1 generation than in the F0 generation. The bioconcentration potential of HBCD diastereoisomers can be ranked in the order α-HBCD>γ-HBCD>ß-HBCD and was found to be higher in T. japonicus than has been reported for fish species.