Effects of diurnally oscillatingp CO 2 on the calcification and survival of coral recruits

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Dufault, Aaron M., Cumbo, Vivian R., Fan, Tung-Yung, Edmunds, Peter J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2012
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1098/rspb.2011.2545; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2011.2545; https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2011.2545

Manipulative studies have demonstrated that ocean acidification (OA) is a threat to coral reefs, yet no experiments have employed diurnal variations in p CO 2 that are ecologically relevant to many shallow reefs. Two experiments were conducted to test the response of coral recruits (less than 6 days old) to diurnally oscillating p CO 2 one exposing recruits for 3 days to ambient (440 µatm), high (663 µatm) and diurnally oscillating p CO 2 on a natural phase (420–596 µatm), and another exposing recruits for 6 days to ambient (456 µatm), high (837 µatm) and diurnally oscillating p CO 2 on either a natural or a reverse phase (448–845 µatm). In experiment I, recruits exposed to natural-phased diurnally oscillating p CO 2 grew 6–19% larger than those in ambient or high p CO 2 . In experiment II, recruits in both high and natural-phased diurnally oscillating p CO 2 grew 16 per cent larger than those at ambient p CO 2 , and this was accompanied by 13–18% higher survivorship; the stimulatory effect on growth of oscillatory p CO 2 was diminished by administering high p CO 2 during the day (i.e. reverse-phased). These results demonstrate that coral recruits can benefit from ecologically relevant fluctuations in p CO 2 and we hypothesize that the mechanism underlying this response is highly p CO 2 -mediated, night-time storage of dissolved inorganic carbon that fuels daytime calcification.