Highlights
- Ocean acidification reduced phagocytic activity and hence immunity of mussels.
- The reduced phagocytic activity was associated with lowered energy budget.
- Ocean acidification also reduced byssus strength, extensibility and production.
- Microplastics can aggravate these negative effects of ocean acidification.
- Mussels would be more prone to diseases and dislodgement in future oceans.
Abstract
Ocean acidification may increase the risk of disease outbreaks that would challenge the future persistence of marine organisms if their immune system and capacity to produce vital structures for survival (e.g., byssus threads produced by bivalves) are compromised by acidified seawater. These potential adverse effects may be exacerbated by microplastic pollution, which is forecast to co-occur with ocean acidification in the future. Thus, we evaluated the impact of ocean acidification and microplastics on the health of a common mussel (Mytilus coruscus) by assessing its physiological performance, immunity and byssus properties. We found that ocean acidification and microplastics not only reduced hemocyte concentration and viability due to elevated oxidative stress, but also undermined phagocytic activity of hemocytes due to lowered energy budget of mussels, which was in turn caused by the reduced feeding performance and energy assimilation of mussels. Byssus quality (strength and extensibility) and production were also reduced by ocean acidification and microplastics. To maximize survival with these stressors, the mussels prioritized the synthesis of some byssus proteins (Mfp-4 and Mfp-5) to help maintain adhesion to substrata. Nevertheless, our findings suggest that the future co-occurrence of ocean acidification and microplastic pollution would increase the susceptibility of bivalves to infectious diseases and dislodgement risk, thereby threatening their survival and undermining their ecological contributions to the community.
Huang X., Leung J. Y. S., Hu M., Xu E. G. & Wang Y., in press. Microplastics can aggravate the impact of ocean acidification on the health of a common mussel: insights from physiological performance, immunity and byssus properties. Environmental Pollution. Article (subscription required).
