The effects of environmental contaminants and ocean acidification on reproductive success in marine invertebrates

Abstract

Marine organisms are exposed to a range of environmental stressors, including anthropogenic pollutants and ocean acidification, which may have harmful effects. The reproductive processes of broadcast spawning marine invertebrates are considered to be particularly vulnerable to environmental insults. Predicting the potential impacts of ocean pollution and acidification on reproductive success is essential to anticipate the consequences of predicted marine change. This study evaluated the effects of exposure to the pharmaceutics diclofenac, ibuprofen and sildenafil citrate (Viagra), the metals cadmium and copper, and the endocrine disrupting compound nonylphenol (singly and under simulated ocean acidification scenarios; pH 8.1, 7.9 and 7.7) on sperm motility and fertilisation success of Asterias rubens, Psammechinus miliaris and Arenicola marina. Sperm motility was determined by Computer Assisted Sperm Analysis (CASA) and fertilisation success by the presence of embryonic cleavage at 60 minutes after fertilisation. Sperm motility (percentage of motile sperm and swimming speed) was reduced by nonylphenol concentrations ≥0.1μg/l, diclofenac ≥ 1.0μg/l, cadmium 1000μg/l, copper ≥10μg/l and ocean acidification of pH 7.9 and 7.7. Exposure to ≥ 1.0μg/l of ibuprofen only affected P. miliaris sperm. Exposure of sperm of A. rubens and P. miliaris to sildenafil citrate at concentrations ≥ 18ng/l and ≥ 50ng/l respectively increased both percentage motility and swimming velocity. Sperm pre-incubated in test conditions prior to fertilisation showed significant reductions in fertilisation success in all single pollutant and ocean acidification scenarios with the exception of ibuprofen for which only P. miliaris was negatively affected. Pre-incubation with sildenafil citrate significantly increased fertilisation success of A. rubens and P. miliaris but not for A. marina. Curiously, the pre-incubated oocytes of P. miliaris, A. rubens and A. marina appeared remarkably robust to some of the pollutants at ambient pH. However, fertilisation was significantly inhibited when exposed to diclofenac, copper, cadmium and seawater pH 7.9 and 7.7 as single stressors. Fertilisation success of P. miliaris and A. marina was adversely affected by sperm-oocyte incubation of ≥20 minutes with 100μg/l and 100μg/l of ibuprofen respectively. Combined nonylphenol and elevated seawater pH significantly reduced sperm motility and fertilisation success. These results demonstrate the potential for marine invertebrates to be affected by single pollutants and suggest that these effects may be more severe under predicted ocean acidification conditions.