Collaborative research: Sinking rates and nutritional quality of organic mater exported from sea ice; the importance of exopolymeric substances

关于冰藻下沉速度的现有数据差异很大，而海冰中其他大型有机池子形成的颗粒的特征几乎没有得到研究。作为纠正这种情况的第一步，提供了资金来研究由冰藻产生的胞外多聚物质(EPS)在颗粒形成中的作用。对于温带水柱，EPS对颗粒凝聚和沉降率的重要性得到了很好的证实。在海冰中，EPS占总颗粒有机碳的20%-70%，但人们对它们在海冰输出颗粒的下沉速度和组成中的作用知之甚少。在前人研究的基础上，PI预测了EPS对颗粒沉降率的正面和负面影响，具体取决于EPS的量。预计EPS还会增加有机质中碳与氮的比例(C：N)，这是一种营养指标。根据记录在案的第一年北极海冰EPS含量的趋势，PI特别预测冰藻出口后产生的颗粒和冰柱上层的下沉速度较慢，C：N较高。他们还预测，在积雪较厚的地方，下沉速度较慢，C：N较高。他们将测量融化的海冰核心释放出的颗粒的下沉速度，并通过将观测到的下沉速度与冰中EPS浓度等变量相关联来测试他们的假设。将使用显微镜和基于DNA的分子技术来研究海冰群落对不同流动期的贡献的变化。最后，为了帮助解释海冰EPS含量的空间变异性，他们将量化养殖冰藻的EPS产生率作为光照水平的函数。这项工作旨在为理解和预测北极海冰释放的颗粒的下沉速度和营养质量与冰中测量的变量(如雪深、叶绿素、颗粒有机碳和EPS)相关的时空变异性提供一个概念性框架。这项研究所产生的知识将有助于我们理解北冰洋的碳循环，以及如何根据气候变化对其进行修改。

Available data concerning the sinking rates of ice algae are highly divergent, while the characteristics of particles formed from other large organic pools in sea ice have received little study. As an initial step to remedy this situation, funds are provided to study the role of exopolymeric substances (EPS), produced by ice algae, in particle formation. The importance of EPS to particle coagulation and sinking rate is well established for temperate water columns. In sea ice, EPS comprise 20-70% of total particulate organic carbon, but their role in the sinking rate and composition of particles exported from sea ice is poorly understood. Based on previous studies, the PIs predict both positive and negative effects of EPS on particle sinking rate depending on EPS quantity. EPS also is predicted to increase the ratio of carbon to nitrogen (C:N) in the organic matter, which serves as a nutritional indicator. Based on documented trends in the EPS content of first-year Arctic sea ice, the PIs specifically predict slower sinking rates and higher C:N in particles produced after the export of ice algae, and from the upper levels of the ice column. They also predict slower sinking rates and higher C:N where snow cover is thicker. They will measure the sinking rates of particles released from melted sea-ice cores and test their hypotheses by relating the observed sinking rates to variables such as EPS concentration in the ice. Changes in the contribution of the sea-ice community to different flux periods will be investigated using microscopy and DNA-based molecular techniques. Finally, to help explain the spatial variability in the EPS content of sea ice, they will quantify EPS production rates of cultured ice algae as a function of light level. This work is designed to provide a conceptual framework for understanding and predicting spatial and temporal variability in the sinking rates and nutritional quality of particles released from Arctic sea ice in relation to variables measured in the ice such as: snow depth, chlorophyll, particulate organic carbon, and EPS. The knowledge resulting from this study will contribute to our understanding of the Arctic Ocean carbon cycle and how it may be modified in response to climate variability.