Département de Biologie, Québec Océan and Institut de Biologie Intégrative et des Systèmes, Université Laval Québec, QC, Canada ; Takuvik Joint International Laboratory (CNRS UMI-3376), Université Laval Québec, QC, Canada.
Plymouth Marine Laboratory Plymouth, UK.
Front Microbiol. 2014 Sep 29;5:490. doi: 10.3389/fmicb.2014.00490. eCollection 2014.
Polar Oceans are natural CO2 sinks because of the enhanced solubility of CO2 in cold water. The Arctic Ocean is at additional risk of accelerated ocean acidification (OA) because of freshwater inputs from sea ice and rivers, which influence the carbonate system. Winter conditions in the Arctic are of interest because of both cold temperatures and limited CO2 venting to the atmosphere when sea ice is present. Earlier OA experiments on Arctic microbial communities conducted in the absence of ice cover, hinted at shifts in taxa dominance and diversity under lowered pH. The Catlin Arctic Survey provided an opportunity to conduct in situ, under-ice, OA experiments during late Arctic winter. Seawater was collected from under the sea ice off Ellef Ringnes Island, and communities were exposed to three CO2 levels for 6 days. Phylogenetic diversity was greater in the attached fraction compared to the free-living fraction in situ, in the controls and in the treatments. The dominant taxa in all cases were Gammaproteobacteria but acidification had little effect compared to the effects of containment. Phylogenetic net relatedness indices suggested that acidification may have decreased the diversity within some bacterial orders, but overall there was no clear trend. Within the experimental communities, alkalinity best explained the variance among samples and replicates, suggesting subtle changes in the carbonate system need to be considered in such experiments. We conclude that under ice communities have the capacity to respond either by selection or phenotypic plasticity to heightened CO2 levels over the short term.
极地海洋是天然的二氧化碳汇，因为二氧化碳在冷水中的溶解度增强。由于海冰和河流的淡水输入，北极海洋面临着加速酸化的额外风险，这会影响碳酸盐系统。北极的冬季条件很有趣，因为既存在低温，又存在海冰存在时向大气中排放有限的二氧化碳。在没有冰盖的情况下对北极微生物群落进行的早期酸化实验表明，在 pH 值降低的情况下，分类群的优势和多样性会发生变化。卡特林北极调查为在北极冬季后期进行现场冰下酸化实验提供了机会。从埃勒夫·里格内斯岛附近的海冰下采集海水，将群落暴露在三种 CO2 水平下 6 天。与对照和处理组相比，附着部分的系统发育多样性大于原位自由生活部分。在所有情况下，优势类群都是γ变形菌门，但与容器的影响相比，酸化的影响很小。系统发育净关联指数表明，酸化可能降低了某些细菌门内的多样性，但总体上没有明显趋势。在实验群落中，碱度最好地解释了样品和重复之间的差异，这表明在这种实验中需要考虑碳酸盐系统的细微变化。我们的结论是，在冰下，群落具有通过选择或表型可塑性来应对短期高 CO2 水平的能力。
