Quantifying the impact of anthropogenic nutrient imbalance on C flux from freshwater lakes: cellular mechanisms, community assembly and modelling

淡水湖泊是地球上最大的生态系统之一，也是二氧化碳（CO2）和甲烷（CH4）排放的主要来源，这两种气体是两种强大的温室气体。由于人口增长，富氮肥料的使用及其流入淡水湖泊是氮（N）和磷（P）日益失衡的主要原因，这两种关键的常量营养素限制了全球范围内重要生态系统的初级生产和温室气体释放。在过去的40年里，人类活动造成的氮径流的快速增长使磷的输入相形见绌，并使全球氮磷比的平衡从19：1转变为30：1，促使越来越多的湖泊生态系统向磷限制的方向发展。虽然这一趋势可能会继续下去，我们的知识，如何这样的一个rehgenically indued磷限制影响CO2和CH4通量在淡水生态系统中仍然不确定。利用我们最近的发现，P限制似乎减少了蓝藻的能力，CO2固定和甲烷氧化甲烷，我们提出了一个多学科的方法来揭示响应淡水微生物组合中的N：P不平衡和随后的影响，在淡水湖泊中的温室气体排放。

Freshwater lakes are amongst the largest ecosystems on Earth, and a major contributor to both carbon dioxide (CO2) and methane (CH4) emissions, two potent greenhouse gases. The use of nitrogen-rich fertilisers and their runoff into freshwater lakes as a result of human population growth are major contributors to the growing imbalance of nitrogen (N) and phosphorus (P), two key macronutrients limiting primary production and greenhouse gas release from this ecologically important ecosystem at a global scale. The much faster increase of anthropogenic nitrogen runoff has dwarfed the input of phosphorus and shifted the balance of the global N:P ratio from 19:1 to 30:1 in the past four decades, driving more and more lake ecosystems towards phosphorus limitation. Although this trend is likely to continue, our knowledge of how such an anthropogenically indued phosphorus limitation affects CO2 and CH4 flux in freshwater ecosystems remains uncertain. Capitalising on our recent discovery that P limitation appears to reduce the capacity of both cyanobacteria for CO2 fixation and methanotrophs for CH4 oxidation, we propose a multidisciplinary approach to uncover the response to N:P imbalance in freshwater microbial assemblages and subsequent impact on greenhouse gas emissions in freshwater lakes.