We present an analysis of long-term (1988–2103; 26 years) total phosphorus (TP) concentration trends in 81 Swedish boreal lakes subject to minimal anthropogenic disturbance. Near universal increases in dissolved organic carbon (DOC) concentrations and a widespread but hitherto unexplained decline in TP were observed. Over 50% of the lakes (n = 42) had significant declining TP trends over the past quarter century (Sen's slope = 2.5% y^− 1). These declines were linked to catchment processes related to changes in climate, recovery from acidification, and catchment soil properties, but were unrelated to trends in P deposition. Increasing DOC concentrations appear to be masking in-lake TP declines. When the effect of increasing DOC was removed, the small number of positive TP trends (N = 5) turned negative and the average decline in TP increased to 3.9% y^− 1. The greatest relative TP declines occurred in already nutrient poor, oligotrophic systems and TP concentrations have reached the analytical detection limit (1 μg L^− 1) in some lakes. In addition, ongoing oligotrophication may be exacerbated by increased reliance on renewable energy from forest biomass and hydropower. It is a cause of significant concern that potential impairments to lake ecosystem functioning associated with oligotrophication are not well handled by a management paradigm focused exclusively on the negative consequences of increasing phosphorus concentrations.

中文翻译：

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瑞典的北方湖泊中持久且广泛的长期磷含量下降

我们提供了对81个受人为干扰最小的瑞典北方湖泊的长期（1988–2103； 26年）总磷（TP）浓度趋势的分析。观察到溶解有机碳（DOC）浓度几乎普遍增加，TP普遍但迄今无法解释的下降。在过去的四分之一世纪中，超过50％的湖泊（n = 42）的TP趋势显着下降（Sen的斜率= y ^{− 1的}2.5％）。这些下降与与气候变化，酸化恢复和集水区土壤特性有关的集水过程有关，但与磷沉积趋势无关。DOC浓度的增加似乎掩盖了湖中TP的下降。当去除DOC增加的影响时，少量的正TP趋势（N = 5）变为负，并且TP的平均下降增加到3.9％y ^-1。最大的相对TP下降发生在已经缺乏营养的贫营养系统中，并且TP浓度达到分析检测极限（1μgL ^{− 1}）在某些湖泊中。此外，对森林生物量和水力发电的可再生能源的依赖性增加可能会加剧正在进行的低营养化。引起人们极大关注的一个问题是，仅通过关注磷浓度增加带来的负面后果的管理范例无法很好地处理与富营养化相关的湖泊生态系统功能的潜在损害。