Legacy Phosphorus and Implications for Lake Restoration Trajectories

整个北方的湖泊越来越多地受到文化富营养化和随后的水质问题，如有害藻华的影响。在过去的几十年中，已经做出了重大努力，以减少来自城市，农业和工业来源的营养素投入。然而，人们现在认识到，历史上的养分输入，特别是磷，积累在流域土壤和湖泊沉积物。这些遗留的磷源有可能影响生态系统的过程，并影响湖泊恢复的目标和轨迹，即使在外部营养源已经解决。最近的几项研究还强调了湖泊系统如何受到并将继续受到气候变化的影响。气温的升高和降水模式的改变导致了北方半球湖泊冰层覆盖的减少和温度分层的延长。这可能导致更多的缺氧沃茨脱氧，这创造了一个环境，有利于释放以前结合磷从湖泊沉积物中的过程称为内部加载。由于沉积物中磷的释放机制受到一系列物理、化学和生物因素的影响，因此预测沉积物中磷的存在、大小和持续时间具有挑战性。这项研究计划的长期目标是开发预测北方湖泊系统内部磷负荷的方法，以及这一过程如何受到气候变化、外部磷负荷和工程化湖泊恢复技术的影响。这项建议的短期目标是：（i）确定影响从历史有机废物输入中恢复的湖泊内部磷负荷的关键因素，（ii）建立、改进和验证数学模型以预测内部磷负荷，（iii）开发综合建模方法以预测气候变化将如何影响内部磷负荷，以及（iv）确定湖泊恢复技术，以减少内部磷负荷。该研究计划将重点关注历史上受到有机废物投入影响的两个流域湖泊系统。将在这两个系统中实施现场监测计划，以确定可能影响内部磷释放的关键变量。将收集沉积物岩心，用于进行受控实验室规模的实验，以进一步分离关键的释放机制。这些信息将用于构建和验证模拟湖泊物理过程和沉积物磷流动性的综合模型。然后，验证模型将被用来探索长期趋势，在内部磷负荷和气候变化和湖泊恢复方法将如何影响这个磷源。

Lakes throughout the northern hemisphere are increasingly impacted by cultural eutrophication and subsequent water quality issues such as harmful algal blooms (HABs). During the past several decades significant efforts have been made to reduce nutrient inputs from municipal, agricultural and industrial sources. However, it is now recognized that historical nutrient inputs, in particular phosphorus, have accumulated in watershed soils and lake sediments. These legacy phosphorus sources have the potential to influence ecosystem processes, and affect lake restoration objectives and trajectories, even after external nutrient sources have been addressed. Several recent studies have also highlighted how lake systems are, and will continue to be, impacted by climate change. Warming temperatures, and changing precipitation patterns, are resulting in less ice cover and longer periods of thermal stratification in Northern hemisphere lakes. This can lead to greater deoxygenation of hypolimnetic waters which creates an environment conducive to the release of previously bound phosphorus from lake sediments in a process termed internal loading. Predicting the presence, magnitude and duration of internal phosphorus loading is challenging, as the mechanisms of release from sediments are influenced by a suite of physical, chemical and biological factors. The long term goal of this research program is to develop approaches for predicting internal phosphorus loading in northern lake systems and how this process is influenced by a changing climate, external phosphorus loads, and engineered in-lake restoration techniques. The short term objectives of this proposal are to: (i) identify key factors that influence internal phosphorus loading in lakes recovering from historical organic waste inputs, (ii) build, refine and validate mathematical models to predict internal phosphorus loading, (iii) develop an integrated modeling approach to forecast how climate change will influence internal phosphorus loading, and (iv) identify in-lake restoration techniques to reduce internal phosphorus loading. The research program will focus on two watershed-lake systems that have been historically impacted by organic waste inputs. Field monitoring programs will be implemented in both systems to characterize key variables that could influence internal phosphorus release. Sediment cores will be collected and used to conduct controlled lab-scale experiments to further isolate key mechanisms of release. This information will be used to construct and validate integrated models that simulate lake physical processes and phosphorus mobility from sediments. The validated models will then be used to explore long terms trends in internal phosphorus loading and how climate change and in-lake restoration approaches will influence this phosphorus source.