Microbial community metabolism and carbon budget on glaciers

生命存在于有水的地方，包括极地冰川等栖息地。冰川表面的灰尘在夏季被太阳加热并融化，形成充满水的漏斗状特征。这些被称为冰尘洞的特征，可以覆盖冰川表面的10-15%，被各种微生物殖民，包括细菌和微小的藻类（即，浮游植物），它们受到低至0.1摄氏度的温度。这些条件可能类似于其他行星上的条件。悬浮在表面沃茨的浮游植物被广泛认为是地球上最重要的初级生产者之一。初级生产者吸收二氧化碳，这是一种引起气候变化的温室气体，并将其转化为氧气。相反，所有生物体（例如，细菌和浮游植物）必须通过呼吸过程燃烧能量以满足其基本代谢需求，呼吸过程将氧气转化为二氧化碳。生态系统中呼吸和初级生产之间的平衡是净代谢，其可以是净异养（即，呼吸高于初级生产）或净自养（即，呼吸低于初级生产）。许多湖泊是净异养的，特别是那些营养物质非常贫乏的湖泊。这种净异养是可能的，因为湖泊可以从集水区获得大量的沉降。人们会认为冰川的营养物质也非常贫乏，因此，它们将是异养的（即，它们向大气排放二氧化碳，因为呼吸作用高于初级生产）。然而，我们在这个建议中声称，冰川维持着一个非常活跃的微生物种群，特别是与冰尘洞中的灰尘有关。这是基于我们之前的研究结果，表明细菌丰度和生产以及初级生产比全球海洋中的平均值高出10倍，或者与湿地甚至废水处理相同。我们假设，在冰川的初级生产可以维持所有其他生物的呼吸，因此，冰川是净自养生态系统。这个项目将回答冰川是向大气中吸入还是排出二氧化碳的问题。我们将测量来自北极（高纬度冰川）和阿尔卑斯山（高海拔冰川）的冰，水和灰尘的初级生产和呼吸。这些结果将与营养预算进行比较，我们将确定与冰尘孔中的灰尘相关的微生物是否受到营养或低温的限制。

Life exists wherever there is water, including habitats such as glaciers in the polar regions. Dust on the surface of glaciers is heated by the sun during the summer and melts, forming funnel shaped features filled with water. These features, called cryoconite holes, that can cover up to 10-15% of the glacier surface, are colonized by a diverse range of microorganisms, including bacteria and minute algae (i.e., phytoplankton), which are subjected to temperatures as low as 0.1 degree C. These conditions might be analogous to conditions found on other planets. Phytoplankton suspended in the surface waters are widely acknowledged as among the most important primary producers on the planet. Primary producers take up carbon dioxide, which is one of the greenhouse gases of concern regarding climate change, and convert it to oxygen. Conversely, all organisms (e.g., bacteria and phytoplankton) must burn energy for their basic metabolic requirements through respiratory processes, which convert back oxygen to carbon dioxide. The balance between respiration and primary production in an ecosystem is the net metabolism, which can be either net heterotrophic (i.e., respiration is higher than primary production) or net autotrophic (i.e., respiration is lower than primary production). Many lakes are net heterotrophic, especially lakes that are very poor in nutrients. This net heterotrophy is possible because lakes can receive a large amount of subsides from the catchment area. One would expect that glaciers are also very poor in nutrients, and therefore, they would be heterotrophic (i.e., they are exporting carbon dioxide to the atmosphere since respiration is higher than primary production). However, we claim in this proposal that glaciers sustain a very active microbial population, especially associated with the dust in the cryoconite holes. This is based on our previous results showing that bacterial abundance and production and primary production are 10 times higher than the average values found in the Oceans worldwide or in the same level as wetlands or even wastewater treatments. We hypothesise that primary production in glaciers can sustain respiration of all other organisms and therefore, glaciers are net autotrophic ecosystems. This project will answer the question whether glaciers are pumping in or pumping out carbon dioxide to the atmosphere. We will measure primary production and respiration in the ice, water and dust of glaciers from the Arctic (high latitude glaciers) and the Alps (high altitude glaciers). These results will be compared to nutrient budgets and we will determine if the microbes associated with the dust in the cryoconite holes are limited by nutrients or the low temperatures.