Macrophytes may either stimulate or depress nitrogen-related microbial processes via radial oxygen loss (ROL), production of exudates or uptake of inorganic N. ROL can favor aerobic processes as nitrification, exudates may stimulate denitrification, whereas N assimilation and competition with microbes may depress both processes. We measured rates of potential nitrification (PN) and denitrification (PD) in oligotrophic lacustrine sediments colonized by submersed and emergent macrophytes. Potential rates were also analyzed in adjacent control sediments devoid of vegetation. Aim of the work was to verify if the presence of macrophytes alters the potential activity of nitrifying or denitrifying bacteria. Vertical profiles (0−10 cm depth) of PN and PD rates were measured via oxic (nitrification) and anoxic (denitrification) slurries, where we measured the accumulation of NO_x⁻ from added NH₄⁺ and the production of ³⁰N₂ from added ¹⁵NO₃⁻, respectively. Results suggest that under oligotrophic settings macrophytes produced small effects on potential nitrification and denitrification activities. Despite elevated oxygen release demonstrated for most of the tested macrophytes, nitrification was likely constrained by significant plant-bacteria competition. Potential denitrification was comparatively more stimulated by macrophytes, but we address this result to a general increase of heterotrophic microbial activity in organic-richer vegetated sediments, due to dead root biomass or exudates. The highest PN and PD rates were measured in sediments colonized by Littorella uniflora, likely due to its large underground biomass (root:shoot ratio ∼3.5), root porosity and oxygen leakage.

大型植物可能通过放射状的氧气损失（ROL）刺激或抑制与氮有关的微生物过程，渗出物的产生或吸收无机氮。ROL可能有利于需氧过程，因为硝化作用，渗出物可能刺激反硝化作用，而氮的同化和与微生物的竞争可能会抑制这两个过程。我们测量了被淹没和浮出的大型植物定殖的贫营养湖相沉积物中潜在硝化（PN）和反硝化（PD）的速率。还分析了附近没有植被的对照沉积物中的潜在速率。这项工作的目的是验证大型植物的存在是否会改变硝化细菌或反硝化细菌的潜在活性。PN和PD速率的垂直剖面（0-10厘米深度）是通过氧化（硝化）和缺氧（反硝化）浆液测量的，_X ^-从加入NH ₄ ⁺和生产的³⁰ ñ ₂从加入¹⁵ NO ₃ ^-， 分别。结果表明，在贫营养条件下，大型植物对潜在的硝化作用和反硝化作用产生小的影响。尽管大多数受检植物都释放出高水平的氧气，但硝化作用可能受到植物细菌竞争的限制。大型植物对潜在的反硝化作用进行了比较多的刺激，但由于死根生物量或渗出物的存在，我们将这一结果归因于富含有机物的植物沉积物中异养微生物活性的普遍增加。PN和PD的最高速率是在单花小球藻定居的沉积物中测得的，这可能是由于其地下生物量大（根：茎比为〜3.5），根部孔隙率和氧泄漏所致。