Abstract The over-enrichment of shallow lakes in nutrients has emerged as one of the main causes of water quality deterioration, and is today a major focus of water quality studies worldwide. In the present work, changes in trophic conditions over three decades (1985–2017) in the largest shallow freshwater lake in Central Europe, Lake Balaton, are assessed using the time series of 10 water quality variables measured at 4 sites, one in each basin of the lake. Using combined cluster and discriminant analyses, and assessing each of the four basins of the lake separately, it was possible to divide the history of the lake into three time intervals. Principal component and Sen's slope analyses highlight the fact that the oligotrophization of the lake took place at a different pace in each of these three major time intervals (1985–1994; 1995–2003; 2004–2017) along the lake's major axis. A significant decrease in the concentration of parameters indicating trophic conditions (e.g. chlorophyll-a, soluble reactive phosphorus) was first observed in the western basins, in the proximity of the main water input to the lake, followed by the eastward spread of this phenomenon. At the same time, the importance of external total phosphorus input to the lake was found to decrease eastwards, thereby diminishing its capacity to explain the variance of the water quality parameters in the lake. Over the time period covered by this study, various measures were taken to reduce the nutrient loads to the lake. These were, in the main, successful, as may be seen in the decade-by-decade overview of the lake's trophic state presented here. A brief review of similar cases from around the world only serves to reinforce the conclusion that a drastic reduction in external phosphorus loads arriving in similar shallow lakes will result in their oligotrophization, albeit with a time-lag of at least ten years.

中文翻译：

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中欧最大浅湖巴拉顿湖 30 年来的时空变化和营养状况的驱动因素

摘要 浅水湖泊营养物质过度富集已成为水质恶化的主要原因之一，是当今世界水质研究的主要焦点。在目前的工作中，使用在 4 个地点测量的 10 个水质变量的时间序列评估中欧最大的浅淡水湖巴拉顿湖在过去三十年（1985-2017 年）营养条件的变化，每个盆地一个的湖。使用组合聚类和判别分析，并分别评估湖泊的四个盆地中的每一个，可以将湖泊的历史划分为三个时间间隔。主成分和 Sen 的斜率分析强调了这样一个事实，即湖泊的贫营养化在这三个主要时间间隔（1985-1994；1995-2003；2004-2017) 沿湖的主轴。表明营养条件的参数（例如叶绿素-a、可溶性活性磷）浓度显着下降，首先在西部盆地，靠近湖泊的主要水源输入处观察到，随后这种现象向东扩散。同时，发现外部总磷输入对湖泊的重要性向东降低，从而削弱了其解释湖泊水质参数变化的能力。在本研究涵盖的时间段内，采取了各种措施来减少湖泊的养分负荷。总的来说，这些都是成功的，正如这里介绍的湖泊营养状态的十年又十年概述中所见。