| Summary: | Recent researches, performed in a naturally acidified site (Castello Aragonese d’Ischia - Gulf of Naples, Italy) where volcanic carbon dioxide vents cause long-term changes in seawater carbonate chemistry, lowering the pH from 8.17 down to 6.57, reveal winners and losers within the benthic community. In the same site, we chose to address the impact of ocean acidification on the algal community with an integrated approach by means of ecological, physiological and molecular tools. Qualitative and quantitative changes in algal composition have been detected. Results showed a less structured community at low pH, characterized by few dominant species and the lack of calcareous taxa. Due to their different tolerance to pH variations, three target species (Sargassum vulgare, Dictyota dichotoma and Jania rubens) have been selected to carry out transplant experiments in order to detect short term stress signals. Variations in fluorometry-derived parameters of the photosynthetic performance of these species were detected in situ at different pH conditions by means of a Diving-PAM. In order to understand if the chronic lowering of pH of this site has promoted any local adaptations (morphological and/or genetic), the Dictyota complex species have been selected. Results indicate that our integrated approach is the key factor leading to understand how these changes can drive deteriorations in the structure and function of algal assemblages under the effects of water acidification.
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