北极海域优势种微单胞藻(Micromonas sp.)与其关联菌群的相互作用

以夏季北极海域的优势微藻-微单胞藻(Micromonas sp.,CMPP2099)及其关联菌群为切入点,对这两个重要生态学角色之间的相互关系进行了探索研究。实验选择两种不同生长状态的微单胞藻(指数生长期和稳定生长期);并针对微单胞藻的这两种生长状态,添加外源细菌(单一外源细菌和自然外源细菌)作为实验组。研究发现,无论添加细菌与否,都不会对微单胞藻的生长产生影响,微单胞藻均保持着正常稳定的生长状态,且微单胞藻能够促进细菌的增长。稳定生长期实验组的细菌数量明显高于指数生长期的细菌数量。微单胞藻由于其不具胶体形成的细胞特性,在藻菌共生中并没有发现透明胞外聚合颗粒物(transparent exopolymer particles,TEP)大量存在。添加外源细菌对培养液中的微单胞藻生长、细菌的数量、溶解有机碳(dissolved organic carbon,DOC)、透明胞外聚合颗粒物(TEP)和溶解游离氨基酸(dissovled free amino acid,DFAA)的浓度并无影响,而仅仅由于其所在状态不同存在着差异。该研究初次开展的北极中心海域优势藻种及关联菌群之间关系研究,对极地海洋生态系统中的微食物环有着重要的意义,并为在极地海域中的微食物环-优势浮游植物-微生物种群之间的生态协作提供了实验和理论依据。

Interactions Between Micromonas sp. and Associated Bacteria in the Arctic Sea

The predominant picoplankton of the Arctic is Micromonas sp., which plays a pivotal role in biogeochemical cycles and is an important link showing that the microbial loop affects organic carbon transfer to higher trophic levels and to deep-sea outputs. As one of the key ecological roles in the Arctic Ocean ecosystem, the interaction between Micromonas sp. and associated bacterioplankton has been explored. A series of inocula experiments was undertaken with isolated CCMP2099 Micromonas sp. in an axenic treatment and in one inoculated with marine bacteria. There was no significant effect on the growth of Micromonas sp., whether treated with bacteria or not. The microalgae grew healthily during the experiments and promoted bacterial growth. Bacterial abundance during the stationary phase was higher than during the exponential phase, although it fluctuated occasionally. Adding exogenous bacteria had no obvious effect on algal growth, bacterial numbers, dissolved organic carbon (DOC), transparent exopolymer particles (TEP), and dissolved free amino acids (DFAA). Based on this preliminary study, the interaction between Micromonas sp. and its associated bacteria was discussed in relation to TEP formation, DOC, and DFAA. Algae-bacterial interaction has a significant effect on the microbial loop in the Arctic ecosystem. The results of this study provide an experimental and theoretical basis for microbial loop, phytoplankton, and key microbial community coupling interactions in the Arctic ecosystem.