CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology (SCSIO), Chinese Academy of Sciences, Guangzhou 510301, China; Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China; CAS-HKUST Sanya Joint Laboratory of Marine Science Research, Key Laboratory of Tropical Marine Biotechnology of Hainan Province, Sanya Institute of Oceanology, SCSIO, Sanya 572000, China; Sanya National Marine Ecosystem Research Station, Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences, Sanya 572000, China.
CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology (SCSIO), Chinese Academy of Sciences, Guangzhou 510301, China; Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China; CAS-HKUST Sanya Joint Laboratory of Marine Science Research, Key Laboratory of Tropical Marine Biotechnology of Hainan Province, Sanya Institute of Oceanology, SCSIO, Sanya 572000, China; Sanya National Marine Ecosystem Research Station, Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences, Sanya 572000, China.
Sci Total Environ. 2022 Oct 10;842:156851. doi: 10.1016/j.scitotenv.2022.156851. Epub 2022 Jun 21.
The successful dispersal of coral larvae is vital to the population replenishment and reef recovery and resilience. Despite that this critical early stage is susceptible to ocean warming and acidification, little is known about the responses of coral larvae to warming and acidification across different biological scales. This study explored the influences of elevated temperature (29 °C versus 33 °C) and pCO (500 μatm versus 1000 μatm) on brooded larvae of Pocillopora damicornis at the organismal, cellular and gene expression levels. Heat stress caused bleaching, depressed light-enhanced dark respiration, photosynthesis and autotrophy, whereas high pCO stimulated photosynthesis. Although survival was unaffected, larvae at 33 °C were ten-times more likely to settle than those at 29 °C, suggesting reduced capacity to disperse and differentiate suitable substrate. Remarkably, heat stress induced greater symbiont loss at ambient pCO than at high pCO, while cell-specific pigment concentrations of symbionts at 33 °C increased twofold under ambient pCO relative to high pCO, suggesting pCO-dependent bleaching patterns. Considerable increases in activities of host antioxidants superoxide dismutase (SOD) and catalase (CAT) at 33 °C indicated oxidative stress, whereas lipid peroxidation and caspase activities were contained, thereby restraining larval mortality at 33 °C. Furthermore, the coral host mounted stronger transcriptional responses than symbionts. High pCO stimulated host metabolic pathways, possibly because of the boosted algal productivity. In contrast, host metabolic processes and symbiont photosystem genes were downregulated at 33 °C. Interestingly, the upregulation of extracellular matrix genes and glycosaminoglycan degradation pathway at 33 °C was more evident under ambient pCO than high pCO, suggesting compromised host tissue integrity that could have facilitated symbiont expulsion and bleaching. Our results provide insights into how coral larvae respond to warming and acidification at different levels of biological organization, and demonstrate that ocean acidification can mediate thermal bleaching and gene expression in coral larvae under heat stress.
珊瑚幼虫的成功扩散对于种群补充和珊瑚礁的恢复和弹性至关重要。尽管这一关键的早期阶段易受海洋变暖和酸化的影响，但对于珊瑚幼虫在不同生物尺度上对变暖酸化的反应知之甚少。本研究探讨了高温（29°C 与 33°C）和 pCO（500 μatm 与 1000 μatm）对 P. damicornis 幼虫在个体、细胞和基因表达水平上的影响。热应激导致白化，降低了光增强的暗呼吸、光合作用和自养作用，而高 pCO 刺激了光合作用。虽然存活率不受影响，但在 33°C 下的幼虫比在 29°C 下的幼虫更有可能定居，这表明它们的扩散和分化合适基质的能力降低。值得注意的是，在环境 pCO 下，热应激导致共生体的损失比在高 pCO 下更大，而在环境 pCO 下，33°C 下共生体的细胞特异性色素浓度比高 pCO 下增加了两倍，这表明存在 pCO 依赖性的白化模式。33°C 时，宿主抗氧化剂超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性显著增加，表明存在氧化应激，而脂质过氧化和半胱天冬酶活性受到抑制，从而抑制了 33°C 下的幼虫死亡率。此外，珊瑚宿主的转录反应比共生体更强。高 pCO 刺激宿主代谢途径，可能是由于藻类生产力的提高。相反，在 33°C 下，宿主代谢过程和共生体光合作用基因下调。有趣的是，在环境 pCO 下，33°C 时细胞外基质基因和糖胺聚糖降解途径的上调比高 pCO 下更明显，这表明宿主组织完整性受损，这可能促进了共生体的排出和白化。我们的研究结果提供了关于珊瑚幼虫在不同生物组织层次上对变暖酸化的反应的见解，并表明海洋酸化可以调节热应激下珊瑚幼虫的白化和基因表达。
