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Impact of diurnal temperature fluctuations on larval settlement and growth of the reef coral Pocillopora damicornis

Lei Jiang, You-Fang Sun, Yu-Yang Zhang, Guo-Wei Zhou, Xiu-Bao Li, Laurence J. McCook, Jian-Sheng Lian, Xin-Ming Lei, Sheng Liu, Lin Cai, Pei-Yuan Qian, Hui Huang
2017 Biogeosciences  
<p><strong>Abstract.</strong> Diurnal fluctuations in seawater temperature are ubiquitous on tropical reef flats. However, the effects of such dynamic temperature variations on the early stages of corals are poorly understood. In this study, we investigated the responses of larvae and new recruits of <i>Pocillopora damicornis</i> to two constant temperature treatments (29 and 31<span class="thinspace"></span>°C) and two diurnally fluctuating treatments (28–31 and 30–33<span
more » ... lass="thinspace"></span>°C with daily means of 29 and 31<span class="thinspace"></span>°C, respectively) simulating the 3<span class="thinspace"></span>°C diel oscillations at 3<span class="thinspace"></span>m depth on the Luhuitou fringing reef (Sanya, China). Results showed that the thermal stress on settlement at 31<span class="thinspace"></span>°C was almost negated by the fluctuating treatment. Further, neither elevated temperature nor temperature fluctuations caused bleaching responses in recruits, while the maximum excitation pressure over photosystem II (PSII) was reduced under fluctuating temperatures. Although early growth and development were highly stimulated at 31<span class="thinspace"></span>°C, oscillations of 3<span class="thinspace"></span>°C had little effects on budding and lateral growth at either mean temperature. Nevertheless, daytime encounters with the maximum temperature of 33<span class="thinspace"></span>°C in fluctuating 31<span class="thinspace"></span>°C elicited a notable reduction in calcification compared to constant 31<span class="thinspace"></span>°C. These results underscore the complexity of the effects caused by diel temperature fluctuations on early stages of corals and suggest that ecologically relevant temperature variability could buffer warming stress on larval settlement and dampen the positive effects of increased temperatures on coral growth.</p>
doi:10.5194/bg-14-5741-2017 fatcat:5wjoiljcobg2tnscuarmtqbtwi