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

关于冰藻下沉速率的现有资料分歧很大，而海冰中其他大型有机池形成的颗粒特征的研究很少。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外聚合物质（EPS）在颗粒形成中的作用。对于温带水柱，EPS对颗粒混凝和沉降速率的重要性已得到充分证实。在海冰中，EPS占总颗粒有机碳的20-70%，但它们在海冰输出颗粒的沉降速率和组成中的作用尚不清楚。基于以往的研究，pi预测了EPS对颗粒沉降速率的正负影响，这取决于EPS的数量。EPS还可以提高有机质中碳氮比（C:N），这是一种营养指标。根据记录的北极海冰第一年EPS含量的趋势，pi特别预测了冰藻出口后产生的颗粒中较慢的下沉速率和较高的C:N，并且来自冰柱的上层。他们还预测，在积雪较厚的地方，下沉速度较慢，C:N较高。他们将测量从融化的海冰核中释放出来的颗粒的下沉速度，并通过将观察到的下沉速度与冰中EPS浓度等变量联系起来，来检验他们的假设。海冰群落对不同通量周期的贡献变化将利用显微镜和基于dna的分子技术进行研究。最后，为了帮助解释海冰中EPS含量的空间变异性，他们将量化培养冰藻的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沉降速率和营养质量的时空变化提供一个概念框架，这些变化与冰中测量的变量有关，如雪深、叶绿素、颗粒有机碳和EPS。从这项研究中获得的知识将有助于我们了解北冰洋的碳循环，以及它是如何随着气候变化而改变的。

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.