一种环境敏感型造礁石珊瑚Pocillopora sp.共生虫黄藻和细菌的生态特征

在气候和人类活动的长期影响下,南海珊瑚礁演变出生境各异的珊瑚礁生态系统.珊瑚对特殊生境的适应离不开体内共生微生物类群的调节.分析共生微生物的生态特征有助于了解珊瑚的环境适应机制,同时可以对珊瑚未来的进化趋势做出评估.本研究从南海低纬度的南沙群岛(NS)和西沙群岛(XS)以及相对高纬度的海南陵水(LS)3个珊瑚礁区采集一...

Ecological characteristics of symbiotic Symbiodiniaceae and bacteria in an environmentally sensitive reef-building coral Pocillopora sp.

Under the long-term influence of climate change and human activities, coral reefs have evolved into special ecosystems with different habitats in the South China Sea. However, the adaptation of corals to special habitats is inseparable from the regulation of endosymbiotic microorganisms. The analysis of ecological characteristics of endosymbiotic microorganisms could help to understand the mechanism of coral host adaptation to environmental changes and the evolutionary trend. In this study, an environmentally sensitive reef-building coral Pocillopora sp. was collected from low latitude Nansha Islands (NS) and Xisha Islands (XS) and the relatively high latitude Hainan Lingshui (LS) in the South China Sea. The community composition and cells density, and environmental correlation of key endosymbiotic microorganisms (Symbiodiniaceae and bacteria) were analyzed. The results showed that: (1) there were great differences in the community composition of Symbiodiniaceae subclades among NS, XS, and LS. The dominant subclades in Pocillopora sp. from NS and XS were D1, C1d, and C42 respectively, while those from LS were C42, C1d, C1p, C1, and C1t; (2) the dominant bacterial compositions included Proteobacteria, Bacteroidetes, and Firmicutes in coral samples from different reef areas, while the relative abundance of Cyanobacteria with photosynthetic function increased significantly with the increase of latitude (from 0.95% of NS to 8.18% of LS, p<0.05); (3) in terms of the number of microbial cells in coral, the density of Symbiodiniaceae increased significantly with the increase of latitude (from (3.39±0.49)×105 cells/cm2 to (8.90±0.65)×105 cells/cm2 coral surface area, p=0.001<0.05), and there was also a higher absolute number of 16S rRNA gene copies in endosymbiotic bacteria in the relatively high latitude LS (p=0.001<0.05); (4) the correlation analysis of environmental factors showed that Symbiodiniaceae subclade D1 with potential thermal tolerance was positively correlated with sea surface temperature and transparency, while subclade C42 and Cyanobacteria were significantly negatively correlated with sea surface temperature and positively correlated with nutrient concentration. This study can provide insight into the micro-ecological mechanism of an environmentally sensitive coral Pocillopora sp. adaptation to environmental change and their evolutionary trend in the South China Sea.