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这样一个大的、人口密集的集水区,其水质主要受控于陆地径流,含盐水分层,25年的滞留时间,来自北海的底部氧化水的间歇更新,受低盐度胁迫的稀少动、植物种类,致使波罗的海对外来压力(如营养输入和有毒物质的增加)变化的承受力非常脆弱。本世纪初以来营养输入和初级生产力增加几倍,已引起缺氧海底面积增加,水的透明度下降了2.5～3m,有利于一年生丝状藻类,而损害了粗的多年生藻类——如重要的墨角藻(Fucus vesiculosus),改变了鱼类的群落——从鳕鱼、鲑鱼、梭子鱼和鲈鱼群落向鲱鱼、西鲱、欧鳊和拟鲤群落转变。作为外部氮主要输入源的现有农业必须有所改变,包括:增加土地分块性的林网,增加生物多样性和控制天然有害物,沿河岸种植填闲作物,为获得最佳营养循环而匹配动物密度和作物类型。在现有生态—社会经济模型基础上的综合土地利用,是至今对可持续性农业最有效的策略工具。
The water quality of such a large, densely populated catchment is dominated by land runoff, saltwater stratification, 25-year residence time, intermittent renewal of oxidizing water from the bottom of the North Sea, rare movements under low salinity stress , The species of plants that have made the Baltic Sea vulnerable to changes in external pressures (such as increased nutrient inputs and toxic substances). Nutrient input and primary productivity have multiplied severalfold since the early 2000s, causing an increase in anoxic seafloor areas and a drop in water transparency of 2.5 to 3 m, contributing to annual filamentous algae and damaging crude perennial algae - such as important inks Fucus vesiculosus alters the community of fish - from herds of cod, salmon, barracuda and seabass to herring, sprats, poplars and carp communities. Existing agriculture, which is a major source of external nitrogen, must be changed, including the addition of land plots, increased biodiversity and the control of natural pests and the planting of slack along the riparian banks for optimal nutrient cycling Match animal density and crop type. Integrated land use based on existing ecological-socio-economic models is by far the most effective strategic tool for sustainable agriculture.