PISCES: Patagonian Ice field Shrinkage impacts on Coastal and fjord EcosystemS

横跨地球表面很大一部分的海洋盆地从冰川和冰原接收大量淡水和沉积物。这种淡水输入正在增加，并且将继续增加，因为不断上升的空气和海洋温度加快了冰融化的速度，并刺激了漂浮的冰川舌的崩塌。巴塔哥尼亚冰原是南半球除南极洲外最大的冰原，近几十年来，几乎所有的冰原都变薄退缩了。由于需要预测未来海平面上升和未来人类住区的供水，巴塔哥尼亚融水排放对海洋的物理影响正在得到更好的研究。然而，人们对这种淡水出口的生物层面知之甚少。大型峡湾系统作为巴塔哥尼亚冰川径流和冰排放的接收水，与海水一起，拥有高产的生态系统和相关的渔业。由于几个原因，冰川淡水输入对这些生态系统的影响可能很重要。首先，稀释的冰川融水的输入为浮游植物的生长创造了一个稳定的分层水柱，但同时可能减少垂直混合的营养供应。其次，冰川径流和冰山可能起到“肥料”的作用，富含高度生物可利用的溶解有机质和其他主要营养物质，如铁、磷、氮和硅。最后，冰川径流的高悬浮颗粒物负荷可能具有双重作用，增加了进一步的营养物质，但为峡湾内系统的浮游生物创造了光照限制条件。随着冰川淡水通量的增加，这些对下游生态系统的影响可能会加剧。目前的主要未知因素有：1)冰川向巴塔哥尼亚峡湾生态系统输送营养物和沉积物的规模、特征和时间；2)在全球变暖的情况下，这些投入如何变化；3)下游生态系统生产力和生物多样性对此类投入的敏感性。双鱼座将通过实地研究和生物地球化学模型的结合，验证巴塔哥尼亚冰原FW通量对下游峡湾和海洋生产力有自然施肥影响的假设。双鱼座将在巴塔哥尼亚广泛的纬度样带上产生第一个冰到海洋的河流营养通量和生物反应数据集。这将为管理该区域淡水供应、质量、海洋生态系统和渔业的决策者提供重要的实用工具。

Ocean basins across a large proportion of the Earth's surface receive substantial freshwater and sediment input from glaciers and ice sheets. This freshwater input is increasing and will continue to do so as rising air and ocean temperatures enhance rates of ice melting and stimulate the collapse of floating glacier tongues. This is true of glaciers draining the Patagonian Ice Fields, the largest ice mass in the Southern hemisphere outside of Antarctica, almost all of which have thinned and retreated in recent decades. The physical impacts of Patagonian meltwater discharge on the oceans are becoming better studied, driven by a need to predict future sea level rise and future water supply for human settlements. However, the biological dimension of this freshwater export, is poorly understood. Large fjord systems act as receiving waters for glacial runoff and ice discharge in Patagonia, and together with marine waters, boast highly productive ecosystems and associated fisheries. The impact of glacial freshwater inputs to these ecosystems is likely to be important for several reasons. First, inputs of dilute glacial meltwater create a stable stratified water column for phytoplankton growth, but simultaneously may reduce nutrient supplies from vertical mixing. Second, glacial runoff and icebergs likely act as "fertilisers", being rich in highly bioavailable dissolved organic matter and other major nutrients, such as iron, phosphorus, nitrogen and silicon. Last, the high suspended particulate matter load of glacial runoff is likely to have a dual effect, adding further nutrients but creating light limiting conditions for plankton within inner fjord systems. These impacts on downstream ecosystems are likely to intensify as glacial freshwaer fluxes rise. Key unknowns at present are: 1) the magnitude, character and timing of glacial nutrient and sediment delivery to Patagonian fjord ecosystems; 2) how these inputs may alter in a warming world; and 3) the sensitivity of downstream ecosystem productivity and biodiversity to such inputs. PISCES will test the hypothesis that Patagonian Ice Field FW fluxes have a natural fertilisation impact upon downstream fjord and marine productivity, via a combination of field-based research and biogeochemical modelling. PISCES will generate the first ice-to-ocean dataset of riverine nutrient fluxes and biological response across a broad latitudinal transect in Patagonia. This will provide an important utility for policy makers managing freshwater supply, quality, marine ecosystems and fisheries in the region.