Abstract Nutrient management in the Great Lakes-St. Lawrence basin has focused on the reduction of tributary phosphorus inputs to control lake eutrophication. However, the regional implications of nutrient enrichment on stream eutrophication and management remain understudied. We compared nutrient concentrations and stoichiometric ratios of carbon, nitrogen, and phosphorus to evaluate spatial and temporal patterns in the potential for nutrient limitation in streams of the lower Great Lakes-St. Lawrence basin in Ontario, Canada. Monitoring data from 127 streams was used to describe macronutrient concentrations and stoichiometry over a 10-year period (2007–2016). Nutrient enrichment was widespread as 65% and 68% of studied streams had nitrogen and phosphorus concentrations above regional guidelines, respectively. Macronutrient stoichiometry indicated that 35% of streams were depleted for phosphorus and 65% were co-depleted for nitrogen and phosphorus relative to the Redfield ratio. However, algal production in most streams was likely nutrient saturated such that only 2% of streams showed the potential for phosphorus limitation and 21% for nitrogen and phosphorus co-limitation. Temporal assessment of individual nutrients that were depleted indicated minimal variation within most streams. In contrast, macronutrient stoichiometry was associated with spatial patterns in catchment land-cover whereby a shift from nitrogen and phosphorus co-depletion to phosphorus depletion occurred with increasing agriculture and decreasing natural and wetland cover. Our results suggest that phosphorus reductions alone may be insufficient to manage stream eutrophication in the Great Lakes-St. Lawrence basin and that dual nutrient reductions needed to improve stream conditions may be achievable through land-cover management.

中文翻译：

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大湖区下游下游支流的常量营养素浓度和化学计量的时空模式。劳伦斯盆地

摘要五大湖区的养分管理-圣。劳伦斯盆地一直致力于减少支流磷输入以控制湖泊富营养化。然而，养分富集对河流富营养化和管理的区域影响仍未得到充分研究。我们比较了养分浓度和碳、氮和磷的化学计量比，以评估五大湖下游河流中养分限制潜力的空间和时间模式。加拿大安大略省的劳伦斯盆地。来自 127 条河流的监测数据用于描述 10 年期间（2007-2016 年）的常量营养素浓度和化学计量。养分富集很普遍，因为 65% 和 68% 的研究河流的氮和磷浓度分别高于区域指南。常量营养素化学计量表明，相对于 Redfield 比率，35% 的溪流中的磷被耗尽，65% 的水流中的氮和磷被共同耗尽。然而，大多数溪流中的藻类产量可能是营养饱和的，因此只有 2% 的溪流显示出磷限制的潜力，而 21% 的溪流显示出氮和磷共同限制的潜力。对耗尽的单个营养物质的时间评估表明，大多数河流中的变化很小。相比之下，常量营养素化学计量与集水区土地覆盖的空间模式相关，随着农业的增加和自然和湿地覆盖的减少，发生从氮和磷共同消耗到磷消耗的转变。我们的结果表明，单独减少磷可能不足以控制 Great Lakes-St. 的河流富营养化。劳伦斯盆地和改善河流条件所需的双重养分减少可以通过土地覆盖管理来实现。