Effects on development, sex differentiation and reproduction of Atlantic cod exposed to produced water during early life stages

Abstract

Two long term studies to assess the effects of produced water (0.01-1 %) on the early life stages of cod were performed. Experiment 1 examined the egg to early fry stage (90 days), and experiment 2 examined the early fry stage to juvenile (78 days). Following exposure, the fish were transferred to clean seawater and monitored for two years till sexual maturation. One group of fish from each exposure regimen was used in spawning experiments No effects on hatching success, growth, survival or sexual differentiation were detected for cod (eggs, larvae and fry) exposed to low concentrations of produced water (dilution 1:1000 or 1:10000). Yolk sack larvae were found to be the most sensitive to produced water exposure. Larvae exposed to 1 % produced water showed an inability to start feed, resulting in 100 % mortality. At the fry stage a significant up-regulation of VTG was shown in groups exposed to 1% produced water and estradiol. CYP1A were significantly up-regulated in fry exposed to 1% produced water, and down-regulated after exposure to 10 ppb estradiol. Exposure to 10 ppb estradiol resulted in severe abnormalities of male testis development and many different morphological signs of intersex were observed.