Eutrophication is a major cause of wetland degradation worldwide. In recent decades, reductions in nutrient inputs have led to improvements in water quality in many rivers and lakes in central and northern Europe, but long-term trends are less clear in southern Europe. We conducted the first comprehensive study of water quality in Doñana (SW Spain), one of the most important wetland complexes in Europe and the Mediterranean region. The core area of Doñana is a large shallow, seasonal marsh (UNESCO World Heritage Site—WHS) that floods during rainy, cool winter months, then dries out during the summer. The marsh is fed by three main streams whose catchments are within a Biosphere Reserve but are impacted by greenhouses (for cultivating fruit, irrigated with groundwater), poorly treated urban wastewaters and tourism. From 2013 to 2016, we monitored nutrient (Total P, Total N, PO₄⁻³, NH₄⁺, NO₃⁻, NO₂⁻) and phytoplankton chlorophyll-a (chla) concentrations in surface waters of the Doñana marsh and the three main streams. We quantified changes in greenhouse cover since 1995 using satellite images. Nutrient concentrations in streams were consistently higher than in the marsh, particularly in the Partido and Rocina streams that regularly reached concentrations equivalent to a “bad physico-chemical status” under the EU Water Framework Directive (WFD), and whose catchments suffered a fivefold expansion of greenhouses from 1995 to 2016. The Partido was the most polluted stream, and the most affected by wastewater effluents, and had particularly high concentrations of NH₄⁺ (Geometric Mean = 0.3 mg L⁻¹) and NO₂⁻ (GM = 0.52 mg L⁻¹) across seasons. Patterns in chla concentrations were less consistent, but streams (GM = 6.78 µg L⁻¹) generally had higher concentrations than the marsh (GM = 4.27 µg L⁻¹). Nutrient concentrations in spot samples within the marsh largely depended on a combination of evaporation (as revealed by higher stable isotope δ²H values in the water column) and spatial processes (concentrations increase close to stream entry points, where conductivity is lower). Anthropogenic nutrient pollution in entry streams is a serious problem in Doñana, with extensive stretches too toxic for fish. Reinforcement of policies aimed at reducing nutrient inputs to Doñana are urgently required to meet the biodiversity conservation and environmental objectives for the WHS and WFD, respectively. Paradoxically, the marsh is currently relied upon to purify the water entering from streams.

富营养化是全球湿地退化的主要原因。近几十年来，营养投入的减少已导致中欧和北欧许多河流和湖泊的水质得到改善，但长期趋势在南欧尚不清楚。我们在多纳纳（西班牙西南部）进行了首次水质综合研究，这是欧洲和地中海地区最重要的湿地综合体之一。多纳纳（Doñana）的核心地区是一个大型的浅层季节性沼泽（教科文组织世界遗产站点，WHS），在多雨，凉爽的冬季月份泛滥成灾，然后在夏季干燥。沼泽由三大主要河流供食，其流域位于生物圈保护区内，但受到温室（用于种植水果，地下水灌溉），处理不当的城市废水和旅游业的影响。从2013年到2016年，₄ ^-3，NH ₄ ⁺，NO ₃ ^-，NO ₂ ^- ）和浮游植物叶绿素一个多纳纳沼泽地和三大干流的地表水浓度 我们使用卫星图像量化了自1995年以来温室覆盖的变化。溪流中的营养物含量始终高于沼泽地，特别是在Partido和Rocina溪流中，其营养水平经常达到相当于欧盟水框架指令（WFD）规定的“恶劣的理化状态”的水平，其流域遭受了五倍的扩展从1995年到2016年的温室的党是污染最严重的流，并且受影响最严重的废水流出物，并且具有特别高的浓度的NH ₄ ⁺（几何均值= 0.3毫克的L ^-1）和NO ₂ ^-（GM = 0.52毫克每升^-1）跨季节。chla浓度的模式不太一致，但是溪流（GM = 6.78 µg L ^-1）的浓度通常高于沼泽（GM = 4.27 µg L ^-1）。沼泽内点样品中的营养物浓度在很大程度上取决于蒸发的组合（如由较高的稳定同位素揭示δ ²水柱中的H值）和空间过程（浓度在接近电导率较低的流入口处增加）。在多纳纳，人流中的人为养分污染是一个严重的问题，大范围的延伸对鱼类来说毒性太大。迫切需要加强旨在减少对多纳纳营养投入的政策，以分别实现世界人道主义峰会和世界粮食日的生物多样性保护和环境目标。矛盾的是，目前依靠沼泽来净化从溪流进入的水。