Aix-Marseille University, Université de Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO), UM 110, 13288 Marseille, France.
Aix-Marseille University, Université de Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO), UM 110, 13288 Marseille, France; UMR 6539 Laboratoire des Sciences de l'Environnement Marin (CNRS, UBO, IRD, Ifremer) Institut Universitaire Européen de la Mer (IUEM) Plouzané, France; Takuvik Joint International Laboratory, Laval University (Canada) - CNRS, Département de biologie, Université Laval, Québec G1V 0A6, Québec, Canada.
Sci Total Environ. 2021 May 20;770:145252. doi: 10.1016/j.scitotenv.2021.145252. Epub 2021 Jan 20.
In the framework of the GreenEdge Project (whose the general objective is to understand the dynamic of the phytoplankton spring bloom in Arctic Ocean), lipid composition and viability and stress state of bacteria were monitored in sea ice and suspended particulate matter (SPM) samples collected in 2016 along a transect from sea ice to open water in Baffin Bay (Arctic Ocean). Lipid analyses confirmed the dominance of diatoms in the bottommost layer of ice and suggested (i) the presence of a strong proportion of micro-zooplankton in SPM samples collected at the western ice covered St 403 and St 409 and (ii) a high proportion of macro-zooplankton (copepods) in SPM samples collected at the eastern ice covered St 413 and open water St 418. The use of the propidium monoazide (PMA) method allowed to show a high bacterial mortality in sea ice and in SPM material collected in shallower waters at St 409 and St 418. This mortality was attributed to the release of bactericidal free fatty acids by sympagic diatoms under the effect of light stress. A strong cis-trans isomerization of bacterial MUFAs was observed in the deeper SPM samples collected at the St 403 and St 409. It was attributed to the ingestion of bacteria stressed by salinity in brine channels of ice by sympagic bacterivorous microzooplankton (ciliates) incorporating trans fatty acids of their preys before to be released in the water column during melting. The high trans/cis ratios also observed in SPM samples collected in the shallower waters at St 413 and St 418 suggest the presence of positively or neutrally buoyant extracellular polymeric substances (EPS)-rich particles retained in sea ice and discharged (with bacteria stressed by salinity) in seawater after the initial release of algal biomass. Such EPS particles, which are generally considered as ideal vectors for bacterial horizontal distribution in the Arctic, appeared to contain a high proportion of dead and non-growing bacteria.
在 GreenEdge 项目（其总体目标是了解北极海洋浮游植物春汛的动态）的框架内，监测了 2016 年在巴芬湾（北极海洋）从海冰到开阔水域的一个横断面上采集的海冰和悬浮颗粒物（SPM）样品中的细菌的脂质组成、生存能力和应激状态。脂质分析证实了硅藻在冰的最底层占主导地位，并表明 (i) 在西部被冰覆盖的 St 403 和 St 409 采集的 SPM 样品中存在大量的微型浮游动物，(ii) 在东部被冰覆盖的 St 413 和开阔水域 St 418 采集的 SPM 样品中存在大量的大型浮游动物（桡足类）。使用吖啶橙单加合物（PMA）方法表明，海冰中和在 St 409 和 St 418 较浅水域采集的 SPM 材料中的细菌死亡率很高。这种死亡率归因于光胁迫下共生硅藻释放的杀菌游离脂肪酸。在 St 403 和 St 409 采集的较深 SPM 样品中观察到细菌 MUFA 的强烈顺反异构化。这归因于共生的噬菌性微浮游动物（纤毛类）在冰盐水通道中摄取受盐胁迫的细菌，在融冰过程中将其猎物的反式脂肪酸纳入体内，然后将其释放到水柱中。在 St 413 和 St 418 较浅水域采集的 SPM 样品中观察到的高反式/顺式比值也表明存在带正电荷或中性浮力的富含细胞外聚合物物质（EPS）的颗粒，这些颗粒保留在海冰中，并在藻类生物量最初释放后（带有受盐胁迫的细菌）排入海水中。这些 EPS 颗粒通常被认为是北极细菌水平分布的理想载体，它们似乎含有很大比例的死亡和非生长细菌。
