Ocean acidification Responses Lead to Altered Toxicities of Chronic Coastal Pollutants in Marine Invertebrates

Chair: Philip Boyd

Ceri Lewis(1), Rob Ellis(1), Anna Campbell(1), Mauricio A. Urbina(1), Adam Porter(1), Rod W. Wilson(1)

1 Biosciences Department, University of Exeter, Geoffrey Pope, Stocker Road, Exeter, EX4 4QD, UK.

Background
Ocean acidification (OA) is not happening in isolation but occurring against a background of chronic low-level contamination for many coastal marine environments, yet the potential for OA interactions with coastal contaminants has received very little attention to date. Some contaminants, such as the metal copper, exhibit increased speciation and hence bioavailability within the pH range predicted for the end of the century, hence are predicted to become more toxic under OA. Other contaminants, such as the anti-fouling agent TBT, should become less bioavailable under OA, whilst microplastics, a global contaminant of increasing concern, are relatively inert and hence not predicted to change in bioavailability under OA.

Methods
We have conducted a series of combined OA-contaminant exposures using a range of contaminants such as metals, pharmaceuticals and microplastics to investigate the interactions between these stressors for a number of benthic marine invertebrate species and life-history stages. Our aim was to test the hypothesis that changes in toxicity will be primarily driven by changes in the chemical behaviour and speciation of the contaminant under reduced seawater pH.

Findings
We provide novel evidence that the toxicity effects of a number of priority contaminants are significantly altered when organisms are exposed to them under near-future pCO2. Our results demonstrate that these changes in toxicity are complex, varying between species and life-history stages and are not driven purely by changes in chemical behaviour driven by reduced seawater pH. The physiological responses of the organisms to OA, such as their acid-base regulation capacity and changes in ventilation behaviour, play a key role in these toxicity responses.

Conclusions
Since coastal pollution is widespread the interactions we have demonstrated between an organisms’ response to OA and its response to contaminants have significant implications for current predictions of OA impacts on a wide range of coastal marine invertebrates.