Shen Dandan, Langenheder Silke, Jürgens Klaus
Section of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Warnemünde, Germany.
Department of Ecology and Genetic/Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
Front Microbiol. 2018 Sep 19;9:2188. doi: 10.3389/fmicb.2018.02188. eCollection 2018.
Dispersal can influence the response of bacterial communities to environmental changes and disturbances. However, the extent to which dispersal contributes to the community response in dependence of the character and strength of the disturbance remains unclear. Here, we conducted a transplant experiment using dialysis bags in which bacterioplankton originating from brackish and marine regions of the Saint Lawrence Estuary were reciprocally incubated in the two environments for 5 days. Dispersal treatments were set-up by subjecting half of the microcosms in each environment to an exchange of cells between the marine and brackish assemblages at a daily exchange rate of 6% (v/v), and the other half of microcosms were kept as the non-dispersal treatments. Bacterial 16S rRNA sequencing was then used to examine the diversity and composition of the active communities. Alpha diversity of the marine communities that were exposed to the brackish environment was elevated greatly by dispersal, but declined in the absence of dispersal. This indicates that dispersal compensated the loss of diversity in the marine communities after a disturbance by introducing bacterial taxa that were able to thrive and coexist with the remaining community members under brackish conditions. On the contrary, alpha diversity of the brackish communities was not affected by dispersal in either environment. Furthermore, dispersal led to an increase in similarity between marine and brackish communities in both of the environments, with a greater similarity when the communities were incubated in the brackish environment. These results suggest that the higher initial diversity in the brackish than in the marine starting community made the resident community less susceptible to dispersing bacteria. Altogether, this study shows that dispersal modifies the diversity and composition of the active communities in response to a salinity disturbance, and enables the local adjustment of specific bacteria under brackish environmental conditions.
扩散会影响细菌群落对环境变化和干扰的响应。然而，扩散在多大程度上依赖于干扰的特征和强度对群落响应产生影响仍不清楚。在此，我们使用透析袋进行了一项移植实验，将圣劳伦斯河口咸淡水区域和海洋区域的浮游细菌在两种环境中相互培养5天。通过让每个环境中一半的微观世界以6%（v/v）的日交换率在海洋和咸淡水组合之间进行细胞交换来设置扩散处理，另一半微观世界作为非扩散处理。然后使用细菌16S rRNA测序来检查活跃群落的多样性和组成。暴露于咸淡水环境的海洋群落的α多样性在有扩散时大幅提高，但在没有扩散时下降。这表明扩散通过引入能够在咸淡水条件下与其余群落成员共同繁荣和共存的细菌类群，补偿了干扰后海洋群落多样性的损失。相反，咸淡水群落的α多样性在两种环境中均不受扩散影响。此外，扩散导致两种环境中海洋和咸淡水群落之间的相似性增加，当群落在咸淡水环境中培养时相似性更高。这些结果表明，咸淡水起始群落比海洋起始群落具有更高的初始多样性，使得本地群落对扩散细菌的敏感性更低。总之，本研究表明，扩散会改变活跃群落的多样性和组成以响应盐度干扰，并能在咸淡水环境条件下实现特定细菌的局部调整。
