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

冰藻与胞外多聚体物质(EPS)的结合以及EPS在其他形式的微生物附着中的作用，表明EPS在藻类与冰的附着中起着重要的作用。根据藻类在当地脉动中离开冰层的证据，这种依恋似乎在季节性冰川融化期间时不时地被克服。有证据表明，有几种物理机制可以将藻类从冰层中分离出来，但并不存在能够预测海藻从冰层中释放的定量数据。资金用于支持将在专门设计的冰罐中进行的受控实验室实验与对亚肯色州巴罗附近沿海快速冰底群落的实地观察相结合的研究。这项研究将研究冰藻如何附着在冰上，可能导致藻类从冰中流出的物理过程，以及在不同条件下从冰中释放的颗粒的生物地球化学特征。EPS在将藻类附着到海冰中的作用将通过使用人工创造的、由冰藻定居的海冰的实验来评估。比较富含EPS的冰和化学降解EPS的冰在融化期间从冰中释放藻类的时间进程。其他实验将侧重于可能触发海冰中藻类释放的四个具体机制：a)附着位置的过度密度和损失，b)表面融化水的冲刷，c)光吸收引起的局部加热，以及d)冰下洋流。每种机制都将被实验隔离，以确定其对实验冰盖外藻类通量的影响。对于每一种机制，从冰上触发藻类脉冲所需的最低条件将被量化，以便与现场观察进行比较。在这些实验中，还将测量从冰中释放的颗粒的生物地球化学相关特征，包括：大小、下沉速度以及有机碳、有机氮、叶绿素和EPS浓度。拟议研究的每一年都建议进行补充实地研究。将使用冰和水柱中藻类丰度的时间序列来确定释放事件。通过比较与拟议的四种分离机制有关的物理变量的时间序列，将能够评估可能触发脉冲的因素。附着在冰上的藻类构成了冰盖海洋初级生产的重要部分。因此，了解极地海洋附着和脱离冰层的相关过程将增强我们对极地海洋的食物网、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.