Ecological effects of glacial dust deposition on remote Arctic lakes

由于气候变暖和其他全球环境变化过程，北极正在迅速变化。北极热量收支变化最明显的影响之一是格陵兰冰盖变薄和出口冰川退缩。然而，冰川增加的河流-冰川输出也充满了淤泥，越来越多的证据表明，随着季节性融化的加剧，格陵兰冰盖的这种输出正在增加。这些冰川产生的物质中有一部分流失到海洋系统中，但有很大一部分沉积在冰川沉积平原上，在那里，较细的颗粒被放气并运送到附近的陆地和水生生态系统。重要的是，这些淤泥和放气的灰尘不是惰性的。由于其高营养含量（碳、磷、氮、硅和微量营养素），这种淤泥/灰尘可能具有重要的生态意义，因为邻近的水生和陆地生态系统的营养状况较低。现在有相当多的证据表明，灰尘刺激微生物活动的冰川冰和冰孔（融化的水洞造成的颗粒沉积，增加热量吸收）的冰面上。然而，有没有类似的研究如何冰川派生的灰尘影响湖泊陆地区域内邻近的冰缘，尽管知识，湖泊是热点的碳加工，绝大多数湖泊邻近格陵兰冰盖的水文连接到它不是由融水通道，因此空中传递的灰尘可能是一个重要的，甚至是主要的湖泊营养源。与灰尘相关的营养物对湖泊的施肥刺激了初级生产，从而刺激了碳动力学。在低纬度地区，沙尘进入湖泊对湖泊的地球化学循环有重要影响。然而，在北极，湖泊对区域碳循环很重要，尽管它们没有很好地纳入区域和全球碳预算，但对这些过程的考虑有限。北极湖泊数量众多（其丰度在北纬65-75度之间最高），通常非常缺乏营养，如果灰尘增加湖泊生产力作为气候变化的间接影响，这将是一个积极的结果。这是由于增加碳埋藏的不成比例的影响，从陆地碳循环中去除碳，因此可以抵消变暖。相反，增加对水生生态系统的有机物投入可能会增强湖泊中的微生物分解，刺激湖泊CO2排放。在这项研究中，我们将比较湖泊沿着梯度的灰尘沉积速率在格陵兰岛西南部的冰川产生的灰尘的生态影响，并评估其在区域碳和水生生物群落动态的作用在一系列的时间（每年到百年）和空间尺度（湖泊区域景观）。

The Arctic is changing rapidly as a result of climate warming and other global environmental change processes. One of the most obvious effects of altered Arctic heat budgets is the thinning of the Greenland ice sheet and the retreat of outlet glaciers. However, the increased fluvio-glacial output from glaciers is also laden with silt and there is growing evidence that such output from the Greenland ice sheet is increasing with enhanced seasonal melting. Some of this glacially-derived material is lost to the marine system but a significant part is deposited on glacial outwash plains from where the finer particles are deflated and transported to nearby terrestrial and aquatic ecosystems. Importantly this silt and the deflated dust is not inert. Because of its high nutrient content (carbon, phosphorus, nitrogen, silica and micronutrients), this silt/dust may be ecologically important because of the low nutrient status of adjacent aquatic and terrestrial ecosystems. There is now considerable evidence that dust stimulates microbiological activity on glacial ice and in cryoconite holes (meltwater holes caused by particle deposition which increases heat uptake) on the ice surface. However, there are no comparable studies on how glacially-derived dust influences lakes within terrestrial areas adjacent to the ice margin, despite the knowledge that lakes are hotspots of carbon processing.The vast majority of lakes adjacent to the Greenland ice sheet are not hydrologically connected to it by meltwater channels, and so aerially-delivered dust might be an important or even predominant lake nutrient source. Fertilization of lakes by nutrients associated with dust stimulates primary production and hence carbon dynamics. Dust inputs to lakes at lower latitudes is known to have major impacts on lake biogeochemical cycling. There has, however, been limited consideration of these processes in the Arctic where lakes are important for regional carbon cycling although they are not well integrated into regional and global carbon budgets. Arctic lakes are numerous (their abundance is highest between 65-75 degrees N) and generally very nutrient poor and if dust increases lake productivity as an indirect effect of changing climate, this will be a positive result. This is due to the disproportional effect on increased carbon burial which removes carbon from the terrestrial carbon cycle and hence can offset warming. Conversely, increasing organic matter input to aquatic ecosystems may enhance microbial decomposition in lakes and stimulate lake CO2 emissions. In this study we will compare the ecological effects of glacially-derived dust on lakes along a gradient of dust deposition rates in SW Greenland and assess its role in regional carbon and aquatic community dynamics at a range of temporal (annual to centennial) and spatial scales (lake to regional landscape).