Effet in situ de l’acidification des océans sur la microflore perforante de substrats aragonitiques

Abstract : Up to now, the impact of acidification on the boring microflora of calcifying organisms has only been addressed by Tribollet et al. (2009), in a short-term laboratory experiment. The study by Tribollet et al. (2009) is the first to show an accelerated weathering of limestone substrates by boring microflora when exposed to high partial pressure of carbon dioxide (750 ppm). The present study aims to investigate the impact of acidification on the microflora of two aragonitic substrates in volcanic carbon dioxide vents in Ischia in Italy. Three sites were selected along a gradient of pH and other environmental data (reported by Rodolpho-Metalpa et al. (2011)): a control site (C; pH = 8.02, close to current seawater pH), a S1 site (pH = 7.24) and a S2 site (pH = 7.44). To highlight the impact of ocean acidification on these micro-organimes, their species diversity was determined and several biological parameters were measured. These data were obtained through the realization of thin sections, which were observed under an optical microscope, and selected observations made with scanning electron microscopy. The results of this study are contradictory to the reference study. Indeed, for low pH rate of carbonate dissolution seems slow. To explain the opposition of the two main studies we hypothesize that there is a pH threshold at which bioerosion by boring microflora is slowed. A study on a pH gradient ranging from 8.1 to 7 with increments of 0.1 or 0.2 pH units would help to better understand the influence of ocean acidification on boring microflora
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J. S. Grange. Effet in situ de l’acidification des océans sur la microflore perforante de substrats aragonitiques. [Travaux universitaires] IRD; UPMC. 2012. ⟨ird-01080744⟩

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