Abstract
There is growing evidence that climate change will increase the prevalence of toxic algae and harmful bacteria, which can accumulate in marine bivalves. However, we know little about any possible interactions between exposure to these microorganisms and the effects of climate change on bivalve health, or about how this may affect the bivalve toxin-pathogen load. In mesocosm experiments, mussels, Perna viridis, were subjected to simulated climate change (warming and/or hyposalinity) and exposed to harmful bacteria and/or toxin-producing dinoflagellates. We found significant interactions between climate change and these microbes on metabolic and/or immunobiological function and toxin-pathogen load in mussels. Surprisingly, however, these effects were virtually eliminated when mussels were exposed to both harmful microorganisms simultaneously. This study is the first to examine the effects of climate change on determining mussel toxin-pathogen load in an ecologically relevant, multi-trophic context. The results may have considerable implications for seafood safety.
Highlights
Similar behavioural and physiological responses have been recorded when bivalves were exposed to toxic dinoflagellates, with the strength of these responses often varying with bivalve species, population and geographical location[27,28]
We investigated how the toxin-pathogen load and the mechanisms that underpin the physiological health of the tropical, commercially important, green mussel P. viridis are affected by climate change induced warming and/or hyposalinity and exposure to the pathogenic bacteria Vibrio parahaemolyticus (‘Vibrio’) and/or the PST producing dinoflagellate Alexandrium minutum (‘Alexandrium’)
There were no significant effects of simulated climate change or microorganism exposure, but there was a significant interaction effect on overall mussel toxin-pathogen load (Fig. 1a, Table 1)
Summary
Similar behavioural and physiological responses (e.g. changes to filtration rate, valve closure, growth rate, byssus thread production and MO2) have been recorded when bivalves were exposed to toxic dinoflagellates, with the strength of these responses often varying with bivalve species, population and geographical location[27,28]. Very high bacterial loads, possibly where the immune system is already compromised, can induce further significant changes to the immunobiological response and adversely affect metabolic regulation[33,34,35] Despite these effects on bivalve physiology being relatively well characterised when measured separately, we still know little about possible interactions between the microorganisms on which bivalves feed and the effects of climate change on the physiological processes underpinning the health of marine shellfish. We investigated how the toxin-pathogen load and the mechanisms that underpin the physiological health of the tropical, commercially important, green mussel P. viridis are affected by climate change induced warming and/or hyposalinity and exposure to the pathogenic bacteria Vibrio parahaemolyticus (‘Vibrio’) and/or the PST producing dinoflagellate Alexandrium minutum (‘Alexandrium’). We hypothesised that: i) the effects of warming and hyposalinity would have detrimental effects on metabolic and immunobiological function in P. viridis leading to an increase in mussel toxin-pathogen load; ii) these effects would be magnified when mussels were exposed to pathogenic or toxic microorganisms and; iii) any indirect effects of warming and hyposalinity and exposure to the microbes on the physiological mechanisms would be at least as strong as the direct effects
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