Nilsson Jenny L, Camiolo Sara, Huser Brian, Agstam-Norlin Oskar, Futter Martyn
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden; Ensucon, Gothenburg, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden; Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
Sci Total Environ. 2024 Dec 10;955:177261. doi: 10.1016/j.scitotenv.2024.177261. Epub 2024 Oct 31.
Phosphorus (P) is often a limiting nutrient in freshwaters and most management actions aim to reduce eutrophication associated with excess anthropogenic P inputs. Here, we report on the opposite problem, persistent and widespread oligotrophication (i.e., declining P concentrations) in northern rivers (56-66 N) that appears unrelated to reductions in anthropogenic loading. Over the past forty years, P concentrations and fluxes in rivers draining forest dominated Swedish catchments have declined by nearly 50 %, with steeper declines in nutrient poor locations. Trends are negatively correlated with forest growth, temperature, pH and alkalinity. They are unrelated to trends in calcium, organic carbon and runoff. Declining P trends were strongest in locations draining catchments with shallow, nutrient poor soils and P concentrations in most locations are currently below estimated reference levels. These widespread and ongoing P declines highlight the need for new surface water management paradigms addressing the consequences of both nutrient scarcity and surplus.
磷（P）通常是淡水生态系统中的限制性营养元素，大多数管理措施旨在减少与过量人为磷输入相关的富营养化问题。在此，我们报告一个相反的问题，即北纬56 - 66度的北方河流中出现了持续且广泛的贫营养化现象（即磷浓度下降），这似乎与人为负荷的减少无关。在过去四十年中，瑞典森林覆盖流域河流中的磷浓度和通量下降了近50%，在营养贫瘠地区下降更为显著。这些趋势与森林生长、温度、pH值和碱度呈负相关，与钙、有机碳和径流量的趋势无关，并在土壤浅薄、营养贫瘠的流域中下降趋势最为明显，目前大多数地区的磷浓度低于估计的参考水平。这些广泛且持续的磷浓度下降凸显了制定新的地表水管理模式的必要性，以应对营养物质稀缺和过剩带来的后果。
