Abstract
The influence of salinity on toxicity outcomes has been demonstrated for various contaminants, but has received limited attention for endocrine disrupting chemicals (EDCs). Short-term laboratory tests using small-bodied fish are an important tool for evaluating impacts of EDCs on reproduction. Tests have been developed for both freshwater and estuarine/marine species, providing an opportunity to assess whether concentrations at which small-bodied fish respond to EDCs may be influenced by salinity. We conducted a semi-quantitative review of short-term laboratory tests with small-bodied fish exposed to EDCs, including 59 studies under freshwater conditions (7 species) and 23 studies conducted under saline conditions (5 species). We focused on two model estrogens [17α-ethinylestradiol and 17β-estradiol (E2)], and three androgens (17β-trenbolone, 5α-dihydrotestosterone and 17α-methyltestosterone). The lowest observed adverse effect concentration (LOAECLOW) for key reproductive endpoints was recorded, including sex-steroid and vitellogenin (VTG) levels, fecundity and fertilization. In 65.2% of cases, responses occurred at lower doses under freshwater compared to saline conditions, compared to only 4.3% of cases where fish responded to lower doses under saline conditions. The potential influence of salinity was more pronounced when estrogenic compounds were considered separately, with fish responding to lower doses under fresh compared to saline conditions in 90.5% of cases. Fecundity and E2 level were identified as the most sensitive endpoints for evaluating EDCs regardless of salinity. Interestingly, female VTG levels were a sensitive endpoint under freshwater but not saline conditions. Overall, our results suggest that salinity may be an important factor influencing how small-bodied fish respond to environmental EDCs.
Highlights
A significant response in E2 levels was observed in >65% of experiments. The outcomes of this semi-quantitative review suggest that the salinity at which standard reproductive bioassays are performed may be an important factor influencing effective concentration to endocrine disrupting chemicals (EDCs)
The concentration at which LOAECLOW was observed was more frequently lower when fish were exposed under freshwater conditions compared to saline conditions
This is especially true for the model estrogenic EDCs considered in our analysis (EE2 and E2), and for model androgens (TB, DHT and MT), the response pattern was less apparent
Summary
Observed reproductive impacts in fish exposed to EDCs include changes in biochemical biomarkers such as vitellogenin (VTG) (Jobling et al, 1998), increased rates of intersex (Jobling et al, 1998; Kidd et al, 2007) and changes in sex ratios (Larsson et al, 2000). Such lower-level effects can have major ecological significance for fish, since they have the potential to scale up and can cause population failure (Kidd et al, 2007). It is extremely important to identify factors that may influence the potency of EDCs to fish, so that at-risk populations can be better identified and protected
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