Increasing anthropogenic CO2 emissions are acidifying our oceans to unprecedented levels. Consequences of ocean acidification (OA) in natural environments, where responses of organisms are mediated by the multiple species and environment interactions, remain poorly understood. As recognized trophic markers, fatty acids (FA) are a good tool to study effects of OA in an organism's biochemical composition and energy transfer throughout the food web. Effects of long-term exposure to low pH in the FA composition of benthic communities were studied at a natural CO2 vent in the Galapagos archipelago and compared to control, non-acidified sites. In this study, FA profiles of macroalgae and macroinvertebrates (gastropods, cnidarians and sea urchins) are reported. FA composition between sites differed only in sea urchin gonads: lower relative values of eicosapentaenoic acid (EPA), arachidonic acid (ARA), polyunsaturated/saturated FA ratio and higher relative values of docosahexaenoic acid (DHA), were found in the vent compared to one of the controls. As for the other taxa, the heterogeneity of sample composition limited the interpretation of results and species-specific analysis should be conducted in the future. Overall, the role of low pH in the observed differences could not be established and future studies should be complemented by controlled experiments.Increasing anthropogenic CO2 emissions are acidifying our oceans to unprecedented levels. Consequences of ocean acidification (OA) in natural environments, where responses of organisms are mediated by the multiple species and environment interactions, remain poorly understood. As recognized trophic markers, fatty acids (FA) are a good tool to study effects of OA in an organism's biochemical composition and energy transfer throughout the food web. Effects of long-term exposure to low pH in the FA composition of benthic communities were studied at a natural CO2 vent in the Galapagos archipelago and compared to control, non-acidified sites. In this study, FA profiles of macroalgae and macroinvertebrates (gastropods, cnidarians and sea urchins) are reported. FA composition between sites differed only in sea urchin gonads: lower relative values of eicosapentaenoic acid (EPA), arachidonic acid (ARA), polyunsaturated/saturated FA ratio and higher relative values of docosahexaenoic acid (DHA), were found in the vent compared to one of the controls. As for the other taxa, the heterogeneity of sample composition limited the interpretation of results and species-specific analysis should be conducted in the future. Overall, the role of low pH in the observed differences could not be established and future studies should be complemented by controlled experiments.
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