Is the Large Aral Sea turning meromictic? Tracing the ongoing changes in the physical and biogeochemical regime of the world’s most dynamic lake ecosystem (Large Aral and Meromixis)

大咸海正在转向分流吗？

• 批准号: 429590333
• 负责人: Professor Dr. Georgiy Kirillin
• 金额: --
• 依托单位: Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/429590333?language=en
• 关键词: Large; Aral; Sea; turning; meromictic

Anthropogenic water use and climate change may have drastic negative consequences on lake ecosystems. The most striking example of the fragility of inland waters, “the ecological disaster of the century”, is the Aral Sea. The consequences of the Aral Sea desiccation have not been fully estimated to date. A new finding of the project team, central to the proposed study, was the recent discovery of meromictic (permanent) stratification starting to develop in the largest remaining basin of the Sea, the Large Aral. Our observations in 2015-2018 suggest that the lake is currently undergoing a transitional period of “meromictisation”, accelerated by the water regulation in the inflowing rivers and by climate-driven changes in the regional water budget. Such a transition suggests acute changes in the biogeochemical regime, some of them, such as the rapid increase of methane concentrations in the lake, have already been registered by the project team. In order to quantify the mechanisms of meromictisation and assess its consequences at regional scales, we propose to apply a set field research methods—monitoring of stratification and the oxygen regime, direct estimations of microbial activity, methane concentrations and emissions together with turbulent mass transfer across the water column, stable isotope studies of the water balance—complemented by modeling and remote sensing observations. The present situation in the Large Aral allows us to trace the unprecedented lake ecosystem changes caused by the major threats to inland waters worldwide: increasing water use and climate-driven alteration of the water budget. As such, a timely and detailed investigation of the transformations in the Large Aral ecosystem would provide a “worst-case” scenario for other large terminal lakes of arid regions, threatened by the same anthropogenic drivers. The expected outcome of this project is a quantification of the present mixing regime in the Large Aral as well as an assessment of the future tendency in the seasonal to decadal mixing and its effect on the biogeochemistry, in particular, methane production, and biodiversity.

人为用水和气候变化可能对湖泊生态系统产生严重的负面影响。内陆沃茨脆弱性的最突出例子是咸海，咸海被称为“世纪的生态灾难”。咸海干涸的后果迄今尚未得到充分估计。项目小组的一项新发现对拟议的研究至关重要，即最近发现在咸海最大的剩余海盆----大咸海----开始形成部分混合（永久）分层。我们在2015-2018年的观察表明，该湖目前正在经历一个“非均匀化”的过渡期，流入河流的水调节和气候驱动的区域水预算变化加速了这一过程。这种转变表明，生物地球化学状况发生了急剧变化，其中一些变化，如湖中甲烷浓度的迅速增加，已经被项目小组记录在案。为了量化meromicitisation的机制，并评估其后果在区域尺度上，我们建议应用一套现场研究方法监测分层和氧制度，直接估计微生物的活动，甲烷浓度和排放量连同湍流质量转移的水柱，稳定同位素研究的水平衡补充建模和遥感观测。大咸海目前的状况使我们能够追踪全世界内陆沃茨面临的主要威胁所造成的前所未有的湖泊生态系统变化：用水量增加和气候驱动的水收支变化。因此，对大咸海生态系统的变化进行及时和详细的调查，将为干旱地区受到同样人为驱动因素威胁的其他大型终端湖泊提供“最坏情况”。该项目的预期成果是对大咸海目前的混合状况进行量化，并评估季节性到十年期混合的未来趋势及其对生态地球化学的影响，特别是甲烷生产和生物多样性。