Drospirenone (DRO) is one of the most widely used progestins in contraceptive treatments and hormone replacement therapies. The pharmacokinetics and potential toxicological effects of DRO were investigated in juvenile sea bass (Dicentrarchus labrax) exposed through the diet (0.01–10 μg DRO/g) for up to 31 days. DRO was detected in the blood (4–27 ng/mL) of fish exposed to the highest concentration, with no significant bioaccumulation over time and no alteration of hepatic metabolizing enzymes, namely, CYP1A and CYP3A-catalysed activities and UDP-glucuronyltransferase (UGT). Pregnenolone (P5), progesterone (P4), 17α-hydroxyprogesterone (17P4), 17α-hydroxypregnenolone (17P5), androstenedione (AD) and testosterone (T) were determined in plasma and gene expression of cyp17a1, cyp19a1a and cyp11β analysed by qRT-PCR in gonads. The significant increase in plasmatic levels of 17P5, 17P4 and AD detected after 31 days exposure to 10 ng DRO/g together with the increased expression of cyp17a1 in females evidence the ability of DRO to alter steroid synthesis at low intake concentrations (7 ng DRO/day). However, the potential consequences of this steroid shift for female reproduction remain to be investigated.

Biofouling is a serious threat to marine renewable energy structures and marine aquaculture operations alike. As an alternative to toxic surface coatings, ultrasonic antifouling control has been proposed as an environmentally friendly means to reduce biofouling. However, the impact of ultrasound on fish farmed in offshore structures or in marine multi-purpose platforms, combining renewable energy production and aquaculture, has not yet been assessed. Here we study the impact of ultrasound on the growth and microbiota of farmed European sea bass (Dicentrarchus labrax) under laboratory conditions. Whereas growth and survival were not reduced by ultrasound exposure, microbiological analysis using plate counts and 16S rRNA gene based metataxonomics showed a perturbation of the gill and skin microbiota, including an increase in putative pathogenic bacteria. This warrants further research into the long-term effects of ultrasonic antifouling control on the health and wellbeing of farmed fish.