Mussel (Mytilus edulis) Image courtesy of

The mussel (Mytilus edulis). Image courtesy of Shutterstock.

Combined effects pose a challenge in predicting coastal futures

A new study, led by Dr Ceri Lewis at the University of Exeter, has highlighted physiological differences in the way two keystone species respond to environmental copper toxicity under near-future ocean acidification scenarios, raising concerns that we may be underestimating the impact of ocean acidification on coastal marine species exposed to persistent pollution.

Ocean acidification (OA) is the drop in oceanic pH levels associated with increasing atmospheric CO2 and it is well established that ocean carbonate chemistry has the potential to negatively impact on marine animals and biodiversity.  The effect of copper on marine organisms is important to understand as it has been identified in previous studies as a high risk pollutant.  This is due in part to its abundance in marine coastal ecosystems but also to its toxic effects to marine species even at low concentrations. 

In the present study, published in Nature’s Scientific Reports, multiple physiological and toxicity responses to OA and copper exposure were measured in  two keystone species of economic importance, the mussel, Mytilus edulis and the purple sea urchin, Paracentrotus lividus.  Of importance here, is that these two species respond to the combined effects of OA and copper differently. Whilst both species exhibited increased copper toxicity under the OA scenario, this was much higher in mussels than urchins, with urchins incurring four times less DNA damage than the mussels. This work suggests that the physiological response of the organism to ocean acidification, which differs from species to species, drives the subsequent response to copper in the environment.

Scientists are just starting to investigate how multiple anthropogenic stressors in the oceans might interact with each other and this study adds to the growing body of evidence that OA will interact with other stressors, making the overall impacts of OA difficult to predict from single stressor studies.

Highlighting concerns from the study’s findings, Dr Lewis said "There are other pollutants common in our coastal waters that are pH sensitive within the range for ocean acidification, and this should now be taken into consideration when risk assessing their biological effects, so that we can ‘future proof’ our environmental risk assessment processes".

Article written by Rachel Coppock, Biosciences Press Gang.

Date: 23 February 2016

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