Department of Microbiology and Immunology, Montana State University, Bozeman, Montana 59717, USA.
Great Salt Lake Institute and Department of Biology, Westminster College, Salt Lake City, Utah 84105, USA.
Ecology. 2019 Mar;100(3):e02611. doi: 10.1002/ecy.2611. Epub 2019 Feb 21.
Microbialites, organosedimentary carbonate structures, cover approximately 20% of the basin floor in the south arm of Great Salt Lake, which ranges from ~12 to 15% salinity. Photosynthetic microbial mats associated with these benthic mounds contribute biomass that supports secondary production in the ecosystem, including that of the brine shrimp, Artemia franciscana. However, the effects of predicted increases in the salinity of the lake on the productivity and composition of these mats and on A. franciscana fecundity is not well documented. In the present study, we applied molecular and microcosm-based approaches to investigate the effects of changing salinity on (1) the primary productivity, abundance, and composition of microbialite-associated mats of GSL, and (2) the fecundity and survivability of the secondary consumer, A. franciscana. When compared to microcosms incubated closest to the in situ measured salinity of 15.6%, the abundance of 16S rRNA gene templates increased in microcosms with lower salinities and decreased in those with higher salinities following a 7-week incubation period. The abundance of 16S rRNA gene sequences affiliated with dominant primary producers, including the cyanobacterium Euhalothece and the diatom Navicula, increased in microcosms incubated at decreased salinity, but decreased in microcosms incubated at increased salinity. Increased salinity also decreased the rate of primary production in microcosm assays containing mats incubated for 7 weeks and decreased the number of A. franciscana cysts that hatched and survived. These results indicate that an increase in the salinity of GSL is likely to have a negative impact on the productivity of microbialite communities and the fecundity and survivability of A. franciscana. These observations suggest that a sustained increase in the salinity of GSL and the effects this has on primary and secondary production could have an upward and negative cascading effect on higher-trophic-level ecological compartments that depend on A. franciscana as a food source, including a number of species of migratory birds.
微生物岩，即有机成因的碳酸盐结构，覆盖了大盐湖南叉约 20%的盆底，其盐度范围在 12%到 15%之间。与这些底栖丘相关的光合作用微生物垫为生态系统提供了支持二次生产力的生物量，包括卤虫，卤虫 franciscana。然而，湖泊盐度升高对这些垫子的生产力和组成以及卤虫 franciscana 繁殖力的影响尚未得到很好的记录。在本研究中，我们应用分子和微宇宙的方法来研究盐度变化对（1）大盐湖相关微生物岩的初级生产力、丰度和组成的影响，以及（2）二次消费者卤虫 franciscana 的繁殖力和存活率的影响。与在最接近原位测量的 15.6%盐度的微宇宙相比，在 7 周的孵育期后，较低盐度的微宇宙中 16S rRNA 基因模板的丰度增加，而较高盐度的微宇宙中其丰度减少。在低盐度孵育的微宇宙中，与优势初级生产者相关的 16S rRNA 基因序列的丰度增加，包括蓝藻 Euhalothece 和硅藻 Navicula，但在高盐度孵育的微宇宙中则减少。盐度增加还降低了含有孵育 7 周的垫子的微宇宙中初级生产力的速度，并减少了孵化和存活的卤虫 franciscana 胞囊的数量。这些结果表明，大盐湖盐度的增加可能会对微生物岩群落的生产力以及卤虫 franciscana 的繁殖力和存活率产生负面影响。这些观察结果表明，大盐湖盐度的持续增加以及由此对初级和次级生产力的影响，可能会对依赖卤虫 franciscana 作为食物来源的更高营养级别的生态群落产生向上和负面的级联效应，包括许多迁徙鸟类的物种。
