Baghdasarian Garen, Osberg Andrew, Mihora Danielle, Putnam Hollie, Gates Ruth D, Edmunds Peter J
Biol Bull. 2017 Apr;232(2):123-139. doi: 10.1086/692718. Epub 2017 Jun 6.
This study tested the bleaching response of the Pacific coral Seriatopora caliendrum to short-term exposure to high temperature and elevated partial pressure of carbon dioxide (pCO). Juvenile colonies collected from Nanwan Bay, Taiwan, were used in a factorial experimental design in which 2 temperatures (∼27.6 °C and ∼30.4 °C) and 2 pCO values (∼47.2 Pa and ∼90.7 Pa) were crossed to evaluate, over 12 days, the effects on the densities and physiology of the symbiotic dinoflagellates (Symbiodinium) in the corals. Thermal bleaching, as defined by a reduction of Symbiodinium densities at high temperature, was unaffected by high pCO. The division, or mitotic index (MI), of Symbiodinium remaining in thermally bleached corals was about 35% lower than in control colonies, but they contained about 53% more chlorophyll. Bleaching was highly variable among colonies, but the differences were unrelated to MI or pigment content of Symbiodinium remaining in the coral host. At the end of the study, all of the corals contained clade C Symbiodinium (either C1d or C15), and the genetic variation of symbionts did not account for among-colony bleaching differences. These results showed that high temperature causes coral bleaching independent of pCO, and underscores the potential role of the coral host in driving intraspecific variation in coral bleaching.
本研究测试了太平洋珊瑚小星珊瑚（Seriatopora caliendrum）对短期高温和高二氧化碳分压（pCO₂）暴露的白化反应。从台湾南湾采集的幼年珊瑚群体被用于析因实验设计，其中将2个温度（约27.6℃和约30.4℃）和2个pCO₂值（约47.2帕和约90.7帕）进行交叉，以评估在12天内对珊瑚中共生双鞭毛虫（虫黄藻，Symbiodinium）的密度和生理的影响。高温下虫黄藻密度降低所定义的热白化不受高pCO₂的影响。热白化珊瑚中残留的虫黄藻的分裂或有丝分裂指数（MI）比对照群体低约35%，但它们的叶绿素含量高约53%。白化在不同珊瑚群体间差异很大，但这些差异与珊瑚宿主中残留的虫黄藻的MI或色素含量无关。在研究结束时，所有珊瑚都含有C类虫黄藻（C1d或C15），共生体的遗传变异不能解释群体间的白化差异。这些结果表明高温导致珊瑚白化独立于pCO₂，并强调了珊瑚宿主在驱动珊瑚白化种内变异中的潜在作用。
