Silverstein Rachel N, Cunning Ross, Baker Andrew C
Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.
Miami Waterkeeper, 12568 N. Kendall Drive, Miami, FL 33186, USA.
J Exp Biol. 2017 Apr 1;220(Pt 7):1192-1196. doi: 10.1242/jeb.148239. Epub 2017 Jan 20.
Reef corals are sensitive to thermal stress, which induces coral bleaching (the loss of algal symbionts), often leading to coral mortality. However, corals hosting certain symbionts (notably some members of clade D) resist bleaching when exposed to high temperatures. To determine whether these symbionts are also cold tolerant, we exposed corals hosting either C3 or D1a to incremental warming (+1°C week to 35°C) and cooling (-1°C week to 15°C), and measured photodamage and symbiont loss. During warming to 33°C, C3 corals were photodamaged and lost >99% of symbionts, while D1a corals experienced photodamage but did not bleach. During cooling, D1a corals suffered more photodamage than C3 corals but still did not bleach, while C3 corals lost 94% of symbionts. These results indicate that photodamage does not always lead to bleaching, suggesting alternate mechanisms exist by which symbionts resist bleaching, and helping explain the persistence of D1a symbionts on recently bleached reefs, with implications for the future of these ecosystems.
珊瑚礁珊瑚对热应激敏感，热应激会引发珊瑚白化（即失去藻类共生体），常常导致珊瑚死亡。然而，某些共生体（特别是D类的一些成员）寄生的珊瑚在暴露于高温时能抵抗白化。为了确定这些共生体是否也耐低温，我们将寄生有C3或D1a的珊瑚置于逐渐升温（每周升高1°C至35°C）和降温（每周降低1°C至15°C）的环境中，并测量光损伤和共生体损失情况。在升温至33°C的过程中，C3珊瑚受到光损伤，失去了超过99%的共生体，而D1a珊瑚虽受到光损伤但未白化。在降温过程中，D1a珊瑚比C3珊瑚遭受了更多的光损伤，但仍未白化，而C3珊瑚失去了94%的共生体。这些结果表明，光损伤并不总是导致白化，这表明存在共生体抵抗白化的其他机制，有助于解释D1a共生体在最近白化的珊瑚礁上的持续存在，这对这些生态系统的未来具有重要意义。
