Excess nitrogen (N) loading is one of the main factors causing eutrophication. Biological N fixation (BNF), as a main contributor to N loading, plays a critical role in the N cycle. The N₂ fixation rate (N₂fix) is regulated by many factors and is usually higher under conditions of N deficiency. Most studies have focused on the regulation of factors that influence the N₂fix in specific aquatic ecosystems or artificial conditions, while fewer have focused on large scale such as the latitudinal distribution of N₂fix. To understand the regulation of the N₂fix in latitudinal zones, the key factors, and the underlying mechanism, we compared the N₂fix in 27 lakes located in different latitudinal zones and analyzed the main regulators. The results showed that (1) heterocyst density (D_Het) and the N₂fix were highest in low-temperate lakes and were 2.5–2.7 and 11.6–22.1 times greater than in high-temperate lakes and tropical lakes, respectively, in the 99th quantile; (2) D_Het increased and then decreased with increasing latitude and radiation, and peaked at 30.28° N and 2300 J/cm/d; (3) D_Het was positively correlated with temperature and increased slightly with increasing temperature; (4) N₂fix increased and then decreased with increasing latitude, temperature and radiation, and peaked at 38.8° N, 24.21 °C and 2120 J/cm/d. The results suggest that BNF could be regulated by larger scale factors, e.g., temperature and radiation in latitudinal scale. Compared with high-temperate lakes and tropical lakes, low-temperate lakes may face more difficulties in controlling eutrophication due to the potentially higher N loading from BNF under similar nutrient and morphometric conditions.

过量的氮 (N) 负载是导致富营养化的主要因素之一。生物固氮（BNF）作为氮负荷的主要贡献者，在氮循环中起着至关重要的作用。N ₂固定率（N ₂ fix）受多种因素调节，通常在缺氮条件下较高。大多数研究都集中在特定水生生态系统或人工条件下影响N ₂固定的因素的调节，而较少关注N ₂固定的纬度分布等大尺度。为了解纬度带 N ₂固定的调控、关键因素和潜在机制，我们比较了 N ₂修复了位于不同纬度区域的 27 个湖泊，并分析了主要调节因素。结果表明：（1）低温带湖泊的异囊密度（D _Het）和N ₂固定最高，分别是高温带湖泊和热带湖泊的2.5-2.7倍和11.6-22.1倍。第 99 个分位数；(2) D _Het随着纬度和辐射的增加先升高后降低，在30.28°N和2300 J/cm/d达到峰值；(3) D _Het与温度呈正相关，随温度升高略有增加；(4) N ₂固定随着纬度、温度和辐射的增加而增加然后减少，并在38.8°N、24.21°C和2120 J/cm/d达到峰值。结果表明，BNF 可以受较大尺度因素的调节，例如纬度尺度的温度和辐射。与高温湖泊和热带湖泊相比，由于在相似的养分和形态条件下，BNF 的 N 负荷可能更高，因此在控制富营养化方面可能面临更多困难。