| dc.description.abstract | Active ingredients (AIs), including pesticides and pharmaceuticals, are designed to have a specific mode-of-action (MoA) in target organisms. Despite this, there is substantial evidence of their occurrence in marine environments having the potential to impact non-target species with effects both as a result of, and independent from, their MoA. Furthermore, due to a large proportion of AIs being readily ionisable, there is growing evidence that their uptake and effects are sensitive to environmental parameters such as pH, which can be driven by changes in pCO2, both in natural cycles and as a consequence of anthropogenic activities.
In this thesis I investigate the impacts of 5 common active ingredient contaminants: the selective serotonin reuptake inhibitor fluoxetine; the non-steroidal anti-inflammatory drugs ibuprofen and diclofenac; and the neonicotinoid pesticides imidacloprid and thiamethoxam; on marine invertebrates and investigate aspects such as bioconcentration, effects, and the sensitivity of these organisms to these compounds under changing pCO2-driven pH conditions.
Firstly, fluoxetine was shown to elicit a pharmacological MoA effect in the marine worm Hediste diversicolor through an increase in serotonin concentration of approximately 10 % following exposure to 10 μg L-1 fluoxetine. Fluoxetine was also shown to induce weight loss (up to 2 % at 500 μg L-1 after 72 hours); decrease feeding rates (up to 68 % at 500 μg L-1); and alter multiple metabolic biomarkers. The uptake and effects of fluoxetine here were also shown to be sensitive to feeding mode, with filter feeding worms experiencing up to 130 times greater body burdens of fluoxetine, and consequently greater effects, than deposit feeding worms – a trait-based sensitivity.
In a second series of experiments, an increase in pCO2 (1000 and 3000 μatm vs a 400 μatm control), and consequent reduction in pH from approximately pH 8.1 to pH 7.75 and 7.4 respectively, was shown to alter uptake and depuration profiles and bioconcentration of all 5 active ingredients in the marine worm Hediste diversicolor. Notably, the bioconcentration factor for fluoxetine decreased from 331 at pH 8.1 to 107 at pH 7.4, whereas the reverse trend occurred for ibuprofen, which increased from 31 at pH 8.1 to 121 at pH 7.4. Seawater pH was also shown to alter the MoA effects of some compounds, with fluoxetine only impacting its MoA endpoint, serotonin, at pH 8.1 and thiamethoxam showing a twofold greater decrease in its MoA, acetylcholinesterase activity, at pH 7.4 when compared to pH 7.75 or pH 8.1.
Finally, the neonicotinoid pesticides imidacloprid and thiamethoxam were shown to alter sperm swimming parameters, and consequently fertilisation success, in the sea urchin Paracentrotus lividus, decreasing by 15 % at 0.32 μg L-1 thiamethoxam and 28 % at 2.38 μg L-1 imidacloprid. This was further shown to be sensitive to changes in pCO2 for thiamethoxam, with a twofold greater reduction in curvilinear velocity of sperm; threefold greater reduction in motile sperm; and 64 % greater reduction in fertilisation success at pH 7.75 compared to pH 8.1.
Together these findings outline the importance of assessing the risk of active ingredients to non-target marine invertebrates and demonstrate the need for
consideration of both MoA effects and independent toxicity assays. In addition, the potential for pCO2 and pH to significantly alter the uptake and effects of active ingredients here indicate that their consideration is vital for effective assessment of current and potential future risks of active ingredients in aquatic environments. | en_GB |
