涠洲岛两种石珊瑚在高温胁迫下共生细菌群落结构变化特征

Characteristics of Symbiotic Bacterial Community Structure Changes in Two Species of Stony Corals in Weizhou Island under High Temperature Stress

关键词:  海孔角蜂巢珊瑚  浪花鹿角珊瑚  石珊瑚  共生细菌  致病菌  高温胁迫  珊瑚白化

Key words:  Favites halicora  Acropora cytherea  stony corals  coral-associated bacteria  pathogen  thermal stress  coral bleaching

摘要:

石珊瑚中的块状珊瑚与枝状珊瑚对全球气候变暖胁迫的耐受能力明显不同，但其机制仍不清楚。本研究选择北部湾涠洲岛的一种属于块状珊瑚的海孔角蜂巢珊瑚（Favites halicora）和一种属于枝状珊瑚的浪花鹿角珊瑚（Acropora cytherea）为研究对象，通过室内模拟实验，分析高温胁迫下（26~34℃）2种珊瑚共生细菌群落的响应特征。结果表明：共生细菌多样性具有差异性，A.cytherea共生细菌的多样性随着温度上升变化显著，Shannon指数由2.20变为4.05，而F.halicora变化幅度较小，在2.69~3.19波动；主导细菌存在差异，在门水平上，F.halicora占主导地位的共生细菌为Proteobacteria（29%~73%）、Cyanobacteria（7%~63%）和Bacteroidetes（3%~13%），而A.cytherea为Proteobacteria（49%~90%）、Cyanobacteria（1%~16%）、Bacteroidetes（3%~16%）、Firmicutes（1%~6%）和一个未分类的细菌门unclassified_k_norank（0.6%~21.0%）；升温胁迫时，主导细菌的丰度变化存在差别，Bacteroidetes在F.halicora中显著降低，而在A.cytherea中显著升高，unclassified_k_norank在A.cytherea中也显著升高；随着温度升高，2种珊瑚共生细菌的变化趋势一致，但珊瑚中出现潜在致病菌Vibrio的温度不同，F.halicora在34℃胁迫时出现，A.cytherea在30℃和34℃胁迫时均出现。根据上述结果推测，珊瑚共生细菌的差异性可能是导致块状珊瑚比枝状珊瑚更耐受高温的重要原因。

Abstract:

Massive and branching corals have significantly different endurance capacity to the stress of global warming, but the mechanism remains unclear. In this study, a kind of massive corals (Favites halicora) and a kind of branching corals (Acropora cytherea) in Weizhou Island of Beibu Gulf were selected as the research objects. The response characteristics of two corals symbiotic bacteria communities under high temperature stress (from 26℃ to 34℃) were analyzed by laboratory simulation experiments. The results showed that the diversity of symbiotic bacteria was different. The diversity of A.cytherea symbiotic bacteria varied significantly with the increase of temperature. The Shannon index changed from 2.20 to 4.05, while the variation of F.halicora was small, fluctuating from 2.69 to 3.19. There were differences in dominant bacteria. At the phylum level, the dominant symbiotic bacteria of F.haricora were Proteobacteria (29%-73%), Cyanobacteria (7%-63%) and Bacteroidetes (3%-13%), while the symbiotic bacteria of A.cytherea consisted largely of Proteobacteria (49%-90%), Cyanobacteria (1%-16%), Bacteroidetes (3%-16%), Firmicutes (1%-6%), and unclassified_k_norank (0.6%-21.0%). There was a difference in the abundance of dominant bacteria in warming stress. Bacteroidetes decreased significantly in F.halicora,but increased significantly in A.cytherea,and unclassified_k_norank also increased significantly in A.cytherea. As the temperature increased, the two coral symbiotic bacteria change in the same trend, but the temperature of the potential pathogen Vibrio in the coral was different. F.hanicora appeared at 34℃ stress, and A.cytherea appeared both at 30℃ and 34℃.Based on the above results, it is speculated that the difference in coral-associated bacteria may be an important reason why massive corals are generally more resistant to high temperatures than branching corals.