A mesocosm experiment was conducted to quantify the effects of pH and temperature on an intact marine invertebrate community. Standardised... » More

 A mesocosm experiment was conducted to quantify the effects of pH and temperature on an intact marine invertebrate community. Standardised communities from the low intertidal zone were exposed to one of eight nominal treatments (four pH × two temperature levels). After 60 days exposure communities showed significant changes in structure and diversity. At higher pH levels elevated temperature treatments contained higher species abundances and diversity than the lower temperature treatments. At lower pH levels, elevated temperature treatments had lower species abundances and diversity than lower temperature treatments. These species losses were not randomly distributed through phyla examined. Molluscs showed the greatest reduction in abundance and diversity in response to low pH and elevated temperature, whilst annelid abundance and diversity was mostly unaffected by low pH, but higher at the elevated temperature. Arthropods showed moderately reduced abundance and diversity at low pH and elevated temperature. Nematode abundance increased in response to low pH and elevated temperature, probably due to the reduction of ecological constraints. This mesocosm study supports suggestions that ocean acidification induced changes in marine biodiversity will be driven by differential vulnerability within and between different taxonomic groups and illustrates the importance of considering indirect effects occurring within multispecies assemblages.

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