Effects of elevated dissolved carbon dioxide and perfluorooctane sulfonic acid, given singly and in combination, on steroidogenic and biotransformation pathways of Atlantic cod

Abstract

In the aquatic environments, the predicted changes in water temperature, pO2 and pCO2 could result in hypercapnic and hypoxic conditions in aquatic animals. These conditions are thought to affect several basic cellular and physiological mechanisms. Yet, possible adverse effects of elevated CO2 (hypercapnia) on teleost fish, as well as combined effects with emerging and legacy environmental contaminants are poorly investigated. In this study, juvenile Atlantic cod (Gadus morhua) were divided into groups and exposed to three different water bath PFOS exposure regimes (0 (control), 100 and 200 µg/L) for 5 days at 1hr/day, followed by three different CO2-levels (normocapnia, moderate (0.3%) and high (0.9%)). The moderate CO2 level is the predicted near future (within year 2300) level, while 0.9% represent severe hypercapnia. Tissue samples were collected at 3, 6 and 9 days after initiated CO2 exposure. Effects on the endocrine and biotransformation systems were examined by analyzing levels of sex steroid hormones (E2, T, 11-KT) and transcript expression of estrogen responsive genes (ERα, Vtg-α, Vtg-β, ZP2 and ZP3). In addition, transcripts for xenobiotic metabolizing enzymes (cyp1a and cyp3a) and hypoxiainducible factor (HIF-1α) were analyzed. Hypercapnia alone produced increased levels of sex steroid hormones (E2, T, 11-KT) with concomitant increase of estrogen responsive genes, while PFOS produced weak and time-dependent effects on E2-inducible gene transcription. Combined PFOS and hypercapnia exposure produced increased effects on sex steroid levels as observed for hypercapnia alone, with transcript expression patterns that are indicative of time-dependent interactive effects. Exposure to hypercapnia singly or in combination with PFOS produced modulations of the biotransformation and hypoxic responses that were apparently concentration and time-dependent. Loading plots of principal component analysis (PCA) produced a significant grouping of individual scores according to the exposure scenarios at day 6 and 9. Overall, the PCA analysis produced a unique clustering of variables that signifies a positive correlation between exposure to high PFOS concentration and expression of E2 responsive genes. Notably, this pattern was not evident for individuals exposed to PFOS concentrations in combination with elevated CO2 scenarios. To our knowledge, the present study is the first of its kind, to evaluate such effects using combined exposure to a perfluoroalkyl sulfonate and elevated levels of CO2 saturation, representative of future oceanic climate change, in any fish species or lower vertebrate.

Temperature is the evil twin: effects of increased temperature and ocean acidification on reproduction in a reef fish

“…In a previous experiment, Miller et al (2013) observed an increase in reproduction at elevated CO 2 levels similar to those used in this experiment. A similar increase in reproduction has since been documented in the three-spine stickleback (Schade et al 2014), and elevated CO 2 resulted in increased levels of reproductive hormones in Atlantic cod (Preus-Olsen et al 2014). Together, these results suggest that stimulation of reproduction by elevated CO 2 could occur in a variety of fish species from a range of families.…”

Effect of long-term intergenerational exposure to ocean acidification on ompa and ompb transcripts expression in European seabass (Dicentrarchus labrax)

“…Conversely, proxies based on the analysis of mRNA expression are very useful to investigate the physiological impact of environmental cues on small organisms since they do not require a lot of biological material. Moreover, numerous studies demonstrated that OA-induced physiological disturbances were associated with regulation of gene expression (Cline et al, 2020, Frommel et al, 2020, Hamilton et al, 2017, Huth and Place, 2016, Lai et al, 2017, Mazurais et al, 2020a, Mazurais et al, 2020b, Shrivastava et al, 2019, Preus-Olsen et al, 2014, Tseng et al, 2013, Mittermayer et al, 2019, Michael et al, 2016. In particular, changes in mRNA levels of proteins involved in neural signalling processes have been observed in olfactory systems of fish exposed to OA (Williams et al, 2019, Porteus et al, 2018, including early stages of development (Rong et al, 2018).…”