Nutrient reduction in impacted lowland freshwater systems is ecologically and culturally important. Gaining a greater insight into how lakes respond to lowering nutrient loads and how climate-driven physical limnology affects present and future cycling of available nutrients is important for ecosystem resource management. This study examines the nutrient decline in a hypereutrophic freshwater lake (Rostherne Mere, Cheshire, UK) 25 years after sewage effluent diversion, a uniquely long-term analysis of a recovering nutrient-rich deep lake. Using nutrient, phytoplankton, climate and catchment hydrological monitoring, the contemporary lake system is compared to previous studies from 1990 to 2002. Nutrient change since point source load diversion showed annual average and maximum phosphorus (P) concentrations decreased significantly for the first 10 years (1992: ~ 600 µg P L⁻¹; 2002: ~ 200 µg P L⁻¹), but have since stabilised due to a substantial legacy sediment P internal load. Dissolved inorganic nitrogen (DIN) concentrations have not substantially changed since diversion, resulting in the alteration of the DIN/SRP ratio from a system characterised by N limitation (N:P ~ 5), to one predominantly P limited (N:P > 20). Nutrient changes over this time are shown to drive ecological change, especially in the cyanobacterial and algal communities. Furthermore, very high-resolution monitoring of lake inflow and outflow (every 5 min during 2016) shows that water residence time at this lake is significantly shorter than previously estimated (~ 0.8 years compared to previous estimates of ~ 1.6–2.4 years). Together with long-term data demonstrating that the stratification period at Rostherne Mere has increased by 40 days over the last ~ 50 years (due to later autumnal mixing), we show that a rapid rate of epilimnetic flushing together with a long stratification period substantially reduces the available epilimnetic P during the summer cyanobacterial bloom. This is of growing importance for many such lakes, given widespread climate-driven lengthening of stratification and a national trend of decreasing summer rainfall (decreasing seasonal flushing) but more intense summer storm events (resulting in short-term flushing events).

受影响的低地淡水系统中的养分减少在生态和文化上都很重要。深入了解湖泊如何应对减少的养分负荷以及气候驱动的物理学如何影响当前和未来的可用养分循环对于生态系统资源管理至关重要。这项研究调查了污水流出物转移后25年后的富营养化淡水湖（Rostherne Mere，英国柴郡）中养分的下降，这是一个对养分丰富的深湖进行恢复的独特的长期分析。利用养分，浮游植物，气候和流域水文监测，将现代湖泊系统与1990年至2002年以前的研究进行了比较。^-1 ; 2002：〜200微克PL ^-1），但此后由于大量的传统沉积物P内部负载而稳定下来。自转移以来，溶解的无机氮（DIN）浓度并未发生实质性变化，从而导致DIN / SRP比率从以N限制（N：P〜5）为特征的系统更改为一个以P限制为主的系统（N：P> 20 ）。这段时间的营养变化显示出驱动生态变化的趋势，尤其是在蓝细菌和藻类群落中。此外，对湖泊流入和流出的高分辨率监测（2016年期间每5分钟）显示，该湖的水滞留时间明显短于先前估计的时间（约0.8年，而先前的估计时间为1.6-2.4年）。加上长期数据表明，在过去〜50年中，Rostherne Mere的分层期增加了40天（由于后来的秋季混合），我们表明，表观潮红的快速冲刷和较长的分层期大大降低了夏季蓝细菌开花期间可利用的上表层磷。鉴于广泛的气候驱动的分层延长和全国性的夏季降水减少趋势（季节性冲洗减少）的趋势，但夏季暴雨事件更加强烈（导致短期冲洗事件），这对于许多这样的湖泊变得越来越重要。