Kaijser Willem, Brauer Verena S, Schürings Christian, Lorenz Armin W
Faculty of Biology, Aquatic Ecology, University of Duisburg-Essen, Essen, Germany.
Faculty of Biology, Aquatic Microbiology, University of Duisburg-Essen, Essen, Germany.
PLoS One. 2025 Sep 2;20(9):e0330460. doi: 10.1371/journal.pone.0330460. eCollection 2025.
Macrophytes in lowland rivers have traditionally been studied with a focus on surface water chemistry, particularly nutrients. However, unlike in lakes, the relationship between macrophytes and surface water nutrients in rivers is generally weaker, especially in highly alkaline lowland rivers, which are often found more downstreams. In these systems, elevated sediment nutrient levels may better explain macrophyte community compositions than surface water nutrients alone. This study investigates the associations between macrophytes and sediment pore water nutrients, particularly Total Phosphorus (TP), while also considering hydromorphological factors such as flow velocity and water depth. Sampling was conducted at 76 locations in wadable lowland rivers in North Rhine-Westphalia, Germany, where macrophyte species, surface water chemistry, and sediment pore water chemistry were recorded. Relationships were analysed using Canonical Correspondence Analysis, absolute niche quantification, and a Generalised Linear Mixed Model (GLMM). Despite the potential role of pore water chemistry in macrophyte nutrient uptake, our results indicate that species niches along pore water TP did not strongly differ. Species niches extended to at least 3,000 μg L-1, although they preferred lower concentrations. Instead, hydromorphological variables, particularly water depth and flow velocity, exerted a stronger influence on macrophyte distribution than either surface or pore water nutrients. Tolerant species such as Ceratophyllum demersum and Potamogeton crispus were more prevalent in deeper waters with higher pH levels, while more sensitive species like Glyceria fluitans were found in shallower areas with lower pH levels. The GLMM estimated that the surface water TP concentrations increase by approximately 0.37% for every 1% rise in pore water TP concentrations, suggesting a notable but complex link between sediment and surface water nutrients. These findings highlight the challenges of using macrophytes as indicators of water column and pore water nutrients levels in lowland rivers. The results suggest that either these rivers are nutrient-saturated and dominated by eutrophic species, limiting their bioindication potential, or that macrophyte communities are completely impoverished. Additionally, hydromorphological alterations, such as river straightening and embankments, constrain ecotone habitats and should also be considered in successful river management strategies.
传统上，对低地河流大型植物的研究主要集中在地表水化学，尤其是营养物质方面。然而，与湖泊不同的是，河流中大型植物与地表水营养物质之间的关系通常较弱，尤其是在下游常见的高碱性低地河流中。在这些系统中，沉积物营养水平的升高可能比单独的地表水营养物质更能解释大型植物群落的组成。本研究调查了大型植物与沉积物孔隙水营养物质之间的关联，特别是总磷（TP），同时还考虑了流速和水深等水文形态因素。在德国北莱茵 - 威斯特法伦州可涉渡的低地河流中的76个地点进行了采样，记录了大型植物物种、地表水化学和沉积物孔隙水化学情况。使用典范对应分析、绝对生态位量化和广义线性混合模型（GLMM）分析了各种关系。尽管孔隙水化学在大型植物营养吸收中具有潜在作用，但我们的结果表明，沿着孔隙水总磷的物种生态位差异并不强烈。物种生态位至少延伸到3000μg/L，尽管它们更喜欢较低的浓度。相反，水文形态变量，特别是水深和流速，对大型植物分布的影响比地表水或孔隙水营养物质更强。像金鱼藻和菹草这样的耐受物种在pH值较高的较深水域更为普遍，而像甜茅这样更敏感的物种则出现在pH值较低的较浅区域。GLMM估计，孔隙水总磷浓度每上升1%，地表水总磷浓度大约增加0.37%，这表明沉积物和地表水营养物质之间存在显著但复杂的联系。这些发现凸显了在低地河流中使用大型植物作为水柱和孔隙水营养水平指标的挑战。结果表明，要么这些河流营养饱和且以富营养物种为主，限制了它们的生物指示潜力，要么大型植物群落完全贫瘠。此外，诸如河道取直和筑堤等水文形态改变限制了生态交错带栖息地，在成功的河流管理策略中也应予以考虑。
