Evolution of Biogenic Exopolymer Concentrations and Interaction with Physical Structure in Arctic Sea Ice

外聚合物物质（EPS）由一系列微生物产生的、结构多样的多糖组成，在生物生理学、水生生态学和海洋“生物碳泵”中发挥着重要作用。众所周知，高浓度的EPS会显著改变含有岩石、含水层和沉积物等多种栖息地的水的物理性质。长期以来，在极地海洋中观察到高浓度的EPS。最近在北极海冰中观察到它们的高浓度，其变量未知，对冰中微生物产生的平衡以及通过生物化学转化和在冰-水界面输出的损失知之甚少。PIs还观察到EPS浓度与海冰盐度之间的关系，这表明生物过程与北极海冰物理结构之间存在一种全新的相互作用。从冰芯观测中分离时空变异性的困难阻碍了对EPS产生和损失平衡的环境强迫的理解。冰芯方法既不能阐明冰-水界面生物质结合的关键过程，也不能阐明EPS浓度和盐度协同变化的机制（以及由此产生的环境敏感性）。因此，无法评估北极气候变化对海洋生态、碳循环和通过EPS产生的海冰性质的影响。该基金旨在结合实地观测和海冰增长理论，研究导致高EPS产生的环境因素以及与北极海冰物理特性的相互作用。该小组将在三个冰季的过程中收集和分析快速冰芯样本，以跟踪自养群落和有机物质库的演变。他们将运用海冰生长理论来研究盐潴留的机制和对冰物理性质的生物影响，并开发和应用水柱和冰中叶绿素a的无损原位荧光测量，以观察冰-水界面上生物量结合的关键过程。这项工作将为在冰-水界面上自动获取海冰生物群动态时间序列奠定基础，这将对未来大规模极地海洋生态变化响应气候变化的研究至关重要。

Krembs0221055Exopolymeric substances (EPS) comprise a suite of microbially produced, structurally diverse polysaccharides that play important roles in organismal physiology, aquatic ecology, and the oceanic "biological carbon pump". High concentrations of EPS are known to significantly alter the physical properties of water containing habitats as diverse as rocks, aquifers and sediments.EPS have long been observed in high concentrations in polar seas. They have recently been observed in high concentrations in arctic sea ice with an unknown variable, poorly understood balance of microbial production in the ice and loss via biochemical conversion and export at the ice-water interface. The PIs have also observed a relationship between EPS concentration and sea ice salinity, which indicates a fundamentally new and prospectively consequential interaction between biological processes and the physical structure of Arctic sea ice.The difficulty of separating temporal from spatial variability in ice core observations impedes understanding of environmental forcing of the balance of EPS production and losses. Neither can ice core methods illuminate the key process of biomass incorporation at the ice-water interface, nor the mechanism (and thus environmental sensitivity) underlying the covariation of EPS concentration and salinity. Thus effects of changing arctic climate on marine ecology, carbon cycling, and sea ice properties via EPS production cannot be assessed.This grant sets out to investigate the environmental factors leading to high EPS production and interaction with arctic sea ice physical properties using a combination of field observations and theory for sea ice growth. The group will collect and analyze fast ice core samples over the course of three ice seasons to track the evolution of the autotrophic community and the organic material pool. They will apply theory for the growth of sea ice to investigate the mechanism(s) of salt retention and biological influence on ice physical properties, and develop and apply nondestructive, in situ fluorometric measurements of Chlorophyll a in the water column and in the ice to observe the key process of biomass incorporation at the ice-water interface. This work will build a basis for automated in situ acquisition of time series of the dynamic of sea ice biota across the ice-water interface, which will be essential for future investigations of large scale polar marine ecological changes in response to varying climate.