Role of external inputs of nutrients to aquatic ecosystems in determining prevalence of nitrogen vs. phosphorus limitation of net primary productivity
Role of external inputs of nutrients to aquatic ecosystems in determining prevalence of nitrogen vs. phosphorus limitation of net primary productivity
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DOI：
10.1007/s10533-021-00765-z
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发表时间：
2021-02
期刊：
影响因子：
4
通讯作者：
R. Howarth;F. Chan;D. Swaney;R. Marino;M. Hayn
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文献类型：
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作者：
R. Howarth;F. Chan;D. Swaney;R. Marino;M. Hayn
水生生态系统的净初级生产力是受到氮(N)、磷(P)的限制，还是受到N&P的共同限制，取决于浮游植物对N和P的相对供应与它们对初级生产的基本需求相比，通常以“Redfield”比率为特征。这些基本营养物质的供应受到外部输入和生态系统内生物地球化学过程的影响。在这篇文章中，我们研究了水生系统的外部营养来源以及N-P输入的平衡如何影响营养限制。对于海洋亚热带环流，相对于深海来源的Redfield比值的相对平衡的N和P输入往往导致N和P的近乎共同限制。对于湖泊，外部营养输入主要来自分水岭来源，我们证明了美国各地这些输入的N：P平均比远高于浮游植物所需的N：P比，这可能是那些经历这种平均营养物质负荷的湖泊的P限制的原因之一。分水岭输入对河口和沿海海洋生态系统也很重要，但海洋营养物质来源也是总营养物质负荷的重要因素。海洋中氮和磷的营养来源通常等于或低于雷德菲尔德16：1摩尔的比例，而且可能基本上是这样，特别是在大陆架很宽的地区。这种低氮磷比的沿海海洋营养物质的大量输入是可能使许多沿海海洋生态系统比湖泊更有可能受到氮限制的一个因素。
Whether net primary productivity in an aquatic ecosystem is limited by nitrogen (N), limited by phosphorus (P), or co-limited by N & P is determined by the relative supply of N and P to phytoplankton compared to their elemental requirements for primary production, often characterized by the “Redfield” ratio. The supply of these essential nutrients is affected by both external inputs and biogeochemical processes within the ecosystem. In this paper, we examine external sources of nutrients to aquatic systems and how the balance of N to P inputs influences nutrient limitation. For ocean subtropical gyres, a relatively balanced input of N and P relative to the Redfield ratio from deep ocean sources often leads to near co-limitation by N and P. For lakes, the external nutrient inputs come largely from watershed sources, and we demonstrate that on average the N:P ratio for these inputs across the United States is well above that needed by phytoplankton, which may contribute to P limitation in those lake that experience this average nutrient loading. Watershed inputs are also important for estuaries and coastal marine ecosystems, but ocean sources of nutrients are also significant contributors to overall nutrient loads. The ocean-nutrient sources of N and P are very often at or below the Redfield ratio of 16:1 molar, and can be substantially so, particularly in areas where the continental shelf is wide. This large input of coastal ocean nutrients with a low N:P ratio is one factor that may make N limitation more likely in many coastal marine ecosystems than in lakes.