Tribollet Aline auteur aut IRD Chauvin A. auteur aut IRD Cuet P. auteur aut IRD text journalArticle eng text/pdf born digital access Rising atmospheric CO2 is acidifying the world's oceans, affecting both calcification and dissolution processes in coral reefs. Among processes, carbonate dissolution by bioeroding microflora has been overlooked, and especially its impact on seawater alkalinity. To date, this biogeological process has only been studied using microscopy or buoyant weight techniques. To better understand its possible effect on seawater alkalinity, and thus on reef carbonate budget, an experiment was conducted under various seawater chemistry conditions (2(arag)3.5 corresponding to 440pCO(2) (mu atm)940) at 25 degrees C under night and daylight (200 mu mol photons m(-2)s(-1)) with natural microboring communities colonizing dead coral blocks (New Caledonia). Both the alkalinity anomaly technique and microscopy methods were used to study the activity of those communities dominated by the chlorophyte Ostreobium sp. Results show that (1) the amount of alkalinity released in seawater by such communities is significant and varies between 12.8 +/- 0.7 at (Arag)similar to 2 and 5.6 +/- 0.4mmol CaCO3 m(-2) day(-1) at (Arag)similar to 3-3.5 considering a 12:12 photoperiod; (2) although dissolution is higher at night (similar to 80 vs. 20% during daylight), the process can occur under significant photosynthetic activity; and (3) the process is greatly stimulated when an acidity threshold is reached (pCO(2)920 mu atm vs. current conditions at constant light intensity). We show that carbonate dissolution by microborers is a major biogeochemical process that could dissolve a large part of the carbonates deposited by calcifying organisms under ocean acidification. specialized Biogenic carbonate dissolution Microborers Euendoliths Coral reefs Ocean acidification Seawater alkalinity NOUVELLE CALEDONIE PACIFIQUE SUD 032 036 064 65 2 art. 9 [10 p.] 2019 0172-9179 https://www.documentation.ird.fr/hor/fdi:010074889 10.1007/s10347-018-0548-x 0172-9179 [F B010074889] https://www.documentation.ird.fr/hor/fdi:010074889 https://www.documentation.ird.fr/intranet/publi/2019/01/010074889.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2019-02-04 2025-02-24 fdi:010074889 fre