Bacterial and extracellular polysaccharide content of brine-wetted snow over Arctic winter first-year ice
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During freeze-up and consolidation, sea ice rejects to its surface brine of marine origin that is incorporated into overlying snow. To evaluate the transport of biological components in brines from ice to snow, vertical profiles of temperature, salinity, bacterial abundance, and extracellular polysaccharide substances (EPS) were obtained through snow and first-year sea ice (Barrow, AK) in consecutive winters (2010, 2011). Snow profiles showed strong interannual variation, with 2010 presenting higher values and wider ranges in salinity (0.3–30.9, practical salinity), bacterial abundance (2.8 × 10<sup>2</sup>–1.5 × 10<sup>4</sup> cells mL<sup>− 1</sup>), and particulate EPS (pEPS, 0.04–0.23 glucose equivalents (glu-eq) mg L<sup>− 1</sup>) than 2011 (0–11.9, 2.7 × 10<sup>3</sup>–4.2 × 10<sup>3</sup> cells mL<sup>− 1</sup> and 0.04–0.09 glu-eq mg L<sup>− 1</sup>, respectively). Surface ice also differed interannually, with 2010 presenting again higher salinity (19.4, <em>n</em> = 1), bacterial abundance (5.4 × 10<sup>4</sup>–9.6 × 10<sup>4</sup> cells mL<sup>− 1</sup>) and pEPS (0.13–0.51 glu-eq mg L<sup>− 1</sup>) than 2011 (7.7–11.9, 1.7 × 10<sup>4</sup>–2.2 × 10<sup>4</sup> cells mL<sup>− 1</sup>, and 0.01–0.09 glu-eq mg L<sup>− 1</sup>, respectively). Transport of bacteria and pEPS from sea-ice brines into snow was evident in 2010 but not 2011, a year with more extreme winter conditions of colder temperature, thinner snow, and stronger wind. By size fraction, the smallest EPS (< 0.1 µm) dominated (> 80%) total EPS in both ice and snow; the > 3 µm fraction of EPS in snow appeared to have an atmospheric source. Evaluation of membrane integrity by Live/Dead stain revealed a high percentage (85%) of live bacteria in saline snow, identifying this vast environment as a previously unrecognized microbial habitat. Citation: Ewert,M., S.D.Carpenter, J.Colangelo-Lillis, and J.W.Deming (2013), Bacterial and extracellular polysaccharide content of brine-wetted snow over Arctic winter first-year sea ice, J. Geophys. Res. Oceans, 118, doi:10.1002/jgrc.20055.
在海冰冻结与固结过程中，海冰会将源自海洋的卤水排出至表层，并融入上方积雪中。为评估生物组分经卤水从海冰向积雪的输运过程，研究团队于连续两个冬季（2010年、2011年）在阿拉斯加巴罗（Barrow, AK）区域，通过积雪和一年期海冰采集了温度、盐度、细菌丰度以及细胞外多糖物质（extracellular polysaccharide substances, EPS）的垂直剖面数据。积雪剖面呈现显著年际差异：2010年的盐度（实用盐度范围0.3~30.9）、细菌丰度（2.8×10²~1.5×10⁴ 个·mL⁻¹）以及颗粒态细胞外多糖（particulate EPS, pEPS，范围0.04~0.23 葡萄糖当量（glu-eq）mg·L⁻¹）均高于2011年（对应数值分别为0~11.9、2.7×10³~4.2×10³ 个·mL⁻¹ 与0.04~0.09 glu-eq mg·L⁻¹）。表层海冰同样存在年际差异，2010年的盐度（19.4，n=1）、细菌丰度（5.4×10⁴~9.6×10⁴ 个·mL⁻¹）以及pEPS（0.13~0.51 glu-eq mg·L⁻¹）也均高于2011年（对应数值分别为7.7~11.9、1.7×10⁴~2.2×10⁴ 个·mL⁻¹ 与0.01~0.09 glu-eq mg·L⁻¹）。2010年可明显观测到细菌与pEPS从海冰卤水向积雪的输运过程，但2011年未出现该现象——该年冬季气候条件更为极端，气温更低、积雪更薄且风力更强。按粒径分级的结果显示，海冰与积雪总细胞外多糖中，粒径<0.1 μm的最小EPS组分占比均超过80%；积雪中粒径>3 μm的EPS组分似乎来源于大气。通过Live/Dead染色法评估细胞膜完整性发现，含盐积雪中活细菌占比高达85%，表明这一广袤环境此前未被认知为微生物栖息地。引用格式：Ewert, M., S. D. Carpenter, J. Colangelo-Lillis, and J. W. Deming (2013), 北极冬季一年期海冰上方卤水浸润积雪的细菌与细胞外多糖含量，《地球物理学研究杂志：海洋》（J. Geophys. Res. Oceans），118卷，doi:10.1002/jgrc.20055。
创建时间：
2016-10-21
