Collaborative Research: Attachment/Detachment of Algae to/from Sea Ice: Mechanisms and Consequences for Biogenic Fluxes and Polar Ecosystems

冰藻与胞外聚合物（EPS）的关联以及EPS在其他形式的微生物粘附中的作用表明，EPS在藻类附着于冰中是重要的。 根据藻类以当地脉冲离开冰的证据，这种附着似乎在季节性冰融化期间被偶然地克服。 有证据表明，有几种物理机制可以使藻类从冰中分离出来，但是还没有定量数据可以预测藻类从冰中释放出来。 提供资金支持的研究，结合控制实验室实验，在专门设计的冰槽与现场观察附近的巴罗，AK沿海固定冰底社区。 该研究将探讨冰藻如何附着在冰层上，可能导致冰藻流出冰层的物理过程，以及在不同条件下从冰层中释放出的颗粒的地球化学特征。EPS在冰藻附着在海冰上的作用将通过使用人工制造的冰藻定居的海冰来评估。 将比较富含EPS的冰和具有化学降解EPS的冰在融化期间来自冰的藻类通量的时间过程。 额外的实验将集中在四个特定的机制，可能触发释放藻类从海冰：a）密度过大和附着点的损失，B）冲洗表面融水，c）局部加热由于光吸收，和d）冰下电流。 每种机制都将通过实验分离出来，以确定其对实验冰盖中藻类通量的影响。 对于每一种机制，将量化触发冰中藻类脉冲所需的最低条件，以与实地观察进行比较。 在这些实验中，还将测量从冰中释放的颗粒的地球化学相关特征，包括：大小，下沉率，有机碳，有机氮，叶绿素和EPS浓度。 在拟议的研究中，每年都提出补充实地研究。 冰和水柱中藻类丰度的时间序列将用于确定释放事件。 与四种拟议的分离机制有关的物理变量的时间序列进行比较，将有助于评估可能触发脉冲的因素。附着在冰层上的藻类构成了冰封海洋初级生产的重要部分。 因此，了解与它们附着和脱离冰的过程有关的过程将增强我们对极地海洋食物网、其空间变异性及其对全球气候变化的潜在反应的理解。

The association of ice algae with exopolymeric substances (EPS) and the role of EPS in other forms of microbial adhesion, suggest that EPS are important in algal attachment to ice. This attachment appears to be episodically overcome during seasonal ice melt, based on evidence that algae leave the ice in local pulses. Evidence suggests several physical mechanisms that detach algae from ice, but quantitative data that would allow prediction of algal release from ice do not exist. Funds are provided to support research that combines controlled laboratory experiments in specially-designed ice tanks with field observations of coastal fast-ice bottom communities near Barrow, AK. The research will address how ice algae attach to ice, the physical processes that may cause flux of algae out of the ice, and the biogeochemical characteristics of particles released from ice under different conditions.The role of EPS in attachment of algae to sea ice will be assessed in experiments using artificially-created, sea-ice sheets colonized by ice algae. The time course of algal flux from the ice during melting will be compared between ice enriched in EPS and ice with chemically-degraded EPS. Additional experiments will focus on four specific mechanisms that potentially trigger the release of algae from sea ice: a) excess density and loss of attachment sites, b) flushing by surface meltwater, c) local heating due to light absorption, and d) under-ice currents. Each mechanism will be experimentally isolated to determine its impact on algal flux out of experimental ice sheets. For each mechanism, the minimal conditions necessary to trigger an algal pulse from the ice will be quantified for comparison with field observations. During these experiments, biogeochemically-relevant characteristics of the particles released from the ice will also be measured, including: size, sinking rate, and organic carbon, organic nitrogen, chlorophyll, and EPS concentrations. Complementary field studies are proposed in each year of the proposed research. Time series of algal abundance in the ice and water column will be used to identify release events. Comparison to time series of physical variables relevant to the four proposed detachment mechanisms will allow assessment of the factors that may have triggered the pulses.Algae that are attached to the ice form a significant portion of the primary production in ice-covered seas. Thus, understanding the processes associated with their attachment to and detachment from the ice will enhance our understanding of the food web of polar seas, its spatial variability, and its potential response to global climate change.