Landscape effects of nitrogen on aquatic ecosystems: Achieving a new paradigm for freshwater eutrophication

氮对水生生态系统的景观影响：实现淡水富营养化的新范例

• 批准号: RGPIN-2018-04590
• 负责人: Leavitt, Peter
• 金额: $ 8.52万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=713153
• 关键词: Landscape; effects; nitrogen; aquatic; ecosystems

Human population has doubled since 1950, in part due to a 10-fold increase in agricultural fertilization that has nearly doubled food production. However, farming practices have also raised soil phosphorus (P) content by >200% and created conditions in which agricultural soils are often saturated with P, will remain so for centuries, and supply freshwaters with excess P. Under these conditions, supplies of nitrogen (N) may regulate lake production, degrade water quality, and favour toxic algal blooms. Unfortunately, because N fertilization has also increased 15-fold since 1970, and because more than half of this N is added as urea, a chemical form of N which promotes toxic cyanobacteria, there exists the possibility that continued agricultural development will lead to continental-scale outbreaks of toxic and carcinogenic algae. Furthermore, disproportionate growth of urban centres has increased supplies of chemically-reduced N (as NH4+) creating blooms in many marine and freshwater systems. Given that ~1 billion people lack clean water, we seek to develop and apply a predictive understanding of the consequences of N pollution for freshwaters in Canada and the world. This program will combine ecosystem manipulation, long-term ecological research (LTER), and innovative paleoecology within 3 component projects to quantify how N fluxes regulate the structure and function of prairie freshwaters. First, we will conduct a unique whole-basin fertilization experiment to quantify how urea regulates production, food-web composition, and biogeochemistry of prairie wetlands. Urea represents 50% of all global N fertilizer, yet little is known of its ecosystem-scale impacts on surface waters. Second, we will apply our multi-decadal LTER research in the 52,000 km2 Qu'Appelle River catchment to quantify for the first time the effects on P-rich lakes of reducing the influx of N alone. Here we take advantage of the 2016 upgrade of the Regina sewage treatment plant which has reduced total N influx >50% (>95% of NH4+), but not P (~5% decline), to three P-rich downstream lakes. Comprehensive limnological analysis will be combined with whole-lake mass balances of N, P and C as part of LTER studies at 7 reference and sewage-impacted sites to test the hypothesis that diversion of N alone can improve water quality in P-rich lakes. Finally, we will apply our advanced statistical approaches (e.g., generalized additive models; conditional probability analysis) to new and older paleolimnological time series to determine whether nutrient fertilization initiates different types of catastrophic state change in N-limited (Qu'Appelle lakes) and P-limited lakes (Yahara lakes chain, Madison, WI). Together these projects will provide managers, scientists, governments, and the public with a transformative understanding of the controls of water-quality degradation in P-rich lakes under diverse development scenarios.

自1950年以来，人口已翻了一番，部分原因是农业施肥增加了10倍，粮食生产几乎翻了一番。但是，农业习惯还将土壤磷（P）含量提高了200％，并创造了农业土壤通常饱和P的条件，将持续数百年，并且供应了多余的P。在这些条件下，氮气（N）的供应可以调节湖泊的产量，可以调节湖泊的水质，偏爱毒性的毒性Algal Blooms。 不幸的是，由于N 1970年以来，N受精还增加了15倍，并且由于该氮的一半以上被添加为尿素（一种n的化学形式），n的化学形式促进了有毒的蓝细菌，因此存在持续农业发展的可能性，可能会导致毒性和致癌性藻类的大陆规模爆发。 此外，城市中心的不成比例增长增加了化学降低的N（如NH4+）在许多海洋和淡水系统中产生花朵的供应。鉴于约有10亿人缺乏干净的水，我们寻求发展并应用对n污染对加拿大淡水的后果的预测理解。 该计划将在3个组件项目中结合生态系统操纵，长期生态研究（LTE）和创新的古生态学，以量化N Fluxes如何调节草原淡水的结构和功能。首先，我们将进行独特的全巴蛋白施肥实验，以量化尿素如何调节草原湿地的生产，食品-WEB组成和生物地球化学。尿素占所有全球N肥料的50％，但对其生态系统规模的影响对地表水的影响知之甚少。其次，我们将在52,000 km2 qu'appelle河流集水区中应用多年lter研究，以首次量化对单独减少n个单独涌入的Pich湖的影响。 在这里，我们利用了2016年Regina污水处理厂的升级，该厂减少了n流入量> 50％（> 95％的NH4+），但不降低P（下降约5％），到三个富含P的下游湖泊。 全面的林理论分析将与N，P和C的全湖质量平衡相结合，作为在7个参考和污水冲击部位的LTER研究的一部分，以检验以下假设：单独的N单独转移可以改善富含Pich湖的水质。最后，我们将应用我们的先进统计方法（例如，广义添加剂模型；有条件的概率分析）和旧的古杂志学时间序列来确定营养受精是否启动了N-Limimited（Qu'Appelle Lakes）中不同类型的灾难性状态变化（Qu'Appelle Lakes）和P-Limited Lakes（Yahara Lakes Lakes（Yahara Lakes Lakes Chain，Madison，Madison，Madison，Wi）。这些项目将共同为经理，科学家，政府和公众提供对多样化的开发场景下水质退化的控制的转变理解。