The limiting nutrient for freshwater phytoplankton productivity can vary within and between geographic regions. Understanding how local (i.e., lake and catchment) and regional (i.e., multiple catchment) factors shift the relative importance of nitrogen (N) and phosphorus (P) limitation presents a key research challenge for freshwater ecosystems and may enhance our understanding of how lakes could be managed to control eutrophication. Here, we used in situ microcosm incubations with factorial N and P amendments to determine the type of limitation in 16 lakes across the northeastern United States. Study lakes had similar climate but varied in geography, trophic status, and chemistry. Limitation by both N and P was most common (colimitation n = 5 and serial limitation n = 3); however, we also observed single nutrient N (n = 3) and P limitation (n = 4). The type of limitation was related to background phytoplankton biomass, longitude, and land use. The magnitude of response to combined nutrient enrichment was negatively related to background P concentrations. This multi-lake experiment suggests that both N and P often play a role in regulating productivity and that local and regional characteristics affect nutrient limitation patterns.

淡水浮游植物生产力的限制养分在地理区域内和地理区域之间可能会有所不同。了解局部（即湖泊和集水区）和区域（即多重集水区）因素如何改变氮（N）和磷（P）限制的相对重要性为淡水生态系统提出了关键的研究挑战，并可能加深我们对湖泊的认识可以控制富营养化。在这里，我们使用了因子和N和P修正的原位缩影培养来确定美国东北部16个湖泊的限制类型。研究湖泊的气候相似，但地理，营养状况和化学性质各异。限制由两者的N和P是最常见的（colimitation Ñ  = 5和序列限制Ñ = 3）; 然而，我们也观察到单一养分N（n  = 3）和P限制（n  = 4）。限制的类型与浮游植物的背景生物量，经度和土地利用有关。对复合养分富集的反应幅度与背景磷浓度呈负相关。这项多湖实验表明，氮和磷均经常在调节生产力方面发挥作用，并且局部和区域性状影响养分限制模式。