Effects of diurnally oscillatingpCO₂on the calcification and survival of coral recruits

Abstract

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

Effects of pCO2 on the interaction between an excavating sponge, Cliona varians, and a hermatypic coral, Porites furcata

“…1) may be related to the biotic history of the corals. Putnam andedmunds (2011) andDufault et al (2012) demonstrated that corals from sites that experienced large daily fluctuations in temperature or pCO 2 were often unaffected by elevated levels of these parameters in experimental conditions. The P. furcata fragments used in this experiment were collected from a reef tract on Isla Pastores that, like most reefs inside the archipelago of Bocas del Toro, Panama, lies directly adjacent to a large mangrove habitat (<10 m distance).…”

Technical Note: Controlled experimental aquarium system for multi-stressor investigation of carbonate chemistry, oxygen saturation, and temperature

“…Such active control of each tank will allow for the transition of the system to one with intentional variability in each of the three controlled parameters. There is a growing need to understand the responses of organisms that live in variable environments, whether weekly, daily, or tidal timescales of variability, and how they may change in the future (Andersson and Mackenzie, 2012;Dufault et al, 2012).…”

Buffer Capacity, Ecosystem Feedbacks, and Seawater Chemistry under Global Change

“…Dufault et al [46] exposed newly settled recruits of the coral Seriatopora caliendrum to stable low pCO 2 , stable high pCO 2 , diurnally fluctuating pCO 2 on a natural phase (similar to the regime on the reef flat at Hobihu Reef, Taiwan), or diurnally fluctuating pCO 2 on a reverse phase. The recruits showed higher rates of calcification and growth under the natural phase fluctuating regime and the high pCO 2 regime as compared to the low pCO 2 regime or the reverse phase regime.…”