Abstract The extent of nutrient enrichment over the urbanized shoreline of western Lake Ontario bordering the Cities of Toronto and Mississauga was investigated in 2018. Concentrations of total phosphorus were higher and more wide-ranging compared with nearshore reference areas in eastern Lake Ontario. Area-weighted chlorophyll a was higher over the shoreline from the mouth of the Credit River to Humber Bay west of Toronto Harbour compared with that to the east from the Toronto Beaches to the Rouge River, a pattern also seen broadly in concentrations of phosphorus fractions and nitrates. Concentrations of phosphate measured by mass spectrometry, and using an internal standard to minimize sampling losses, were higher in Toronto Inner Harbour, near wastewater outfalls, river mouths, and to varying extent over the mixing areas of these discharges. Chlorophyll a suggested broadly oligotrophic to oligo-mesotrophic conditions despite areas with nutrient fractions suggestive of more productive conditions. Toronto Inner Harbour was mesotrophic, with wide-ranging levels of phosphorus fractions strongly influenced by the variable loading from the Don River into the harbour. Phosphorus fractions in the harbour quays which also receive CSOs discharges were elevated at times. Blooms or scums of planktonic algae were not observed. Elevated concentrations of phosphate were found at shallow depths suitable for growth of the green algae Cladophora. As these urban areas continue to grow, the potential for additional nutrient loading to exacerbate growth of algae should be watched given the present conditions that indicate variable but pervasive nutrient enrichment.

中文翻译：

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安大略湖多伦多-密西沙加海滨的营养足迹

摘要 2018 年调查了安大略湖西部与多伦多市和密西沙加市接壤的城市化海岸线的养分富集程度。与安大略湖东部的近岸参考区相比，总磷浓度更高，范围更广。与从多伦多海滩到 Rouge 河以东的海岸线相比，从Credit River 河口到多伦多港以西的 Humber Bay 的海岸线上的面积加权叶绿素 a 更高，这种模式也广泛存在于磷部分和硝酸盐。在多伦多内港、废水排放口、河口附近以及在这些排放物的混合区域，通过质谱法测量的磷酸盐浓度较高，并使用内部标准将采样损失降至最低。叶绿素 a 表明广泛的贫营养到贫中营养条件，尽管具有营养成分的区域表明具有更高的生产力条件。多伦多内港是中营养型的，从唐河到港口的可变负荷对磷含量的影响范围很广。港口码头中也接受公民社会组织排放的磷含量有时会升高。没有观察到浮游藻类的水华或浮渣。在适合绿藻 Cladophora 生长的较浅深度处发现磷酸盐浓度升高。随着这些城市地区的不断发展，考虑到目前的条件表明营养物富集可变但普遍存在，应该注意额外的营养负荷以加剧藻类的生长的可能性。