University Duisburg-Essen, Faculty of Biology, Aquatic Ecology, Universitätsstraße 5, D-45141 Essen, Germany.
University Duisburg-Essen, Faculty of Biology, Aquatic Ecology, Universitätsstraße 5, D-45141 Essen, Germany; University Duisburg-Essen, Centre for Water and Environmental Research, Universitätsstraße 5, D-45141 Essen, Germany.
Sci Total Environ. 2021 Aug 10;781:146728. doi: 10.1016/j.scitotenv.2021.146728. Epub 2021 Mar 26.
Nitrogen and phosphorous concentrations are widely considered to drive macrophyte assemblages in rivers. However, Dissolved Inorganic Carbon (DIC) - available for plants as CO and HCO - is also of major relevance. Based on literature, we present a conceptual model on the interaction between algae, macrophytes, DIC, pH, light, N, P and the surface water and sedimental compartment. Analysing two separate datasets (i) on river physico-chemistry and chlorophyll-a, and (ii) on river physico-chemistry and macrophytes we quantify three connections within this concept: (1) the correlation of chlorophyll-a versus pH, (2) the correlation of TP versus chlorophyll-a and (3) the occurrence of HCO-users and CO-only-users among macrophytes along the DIC gradient. Chlorophyll-a correlated positively with pH (R-squared = 77%, p < .001) due to increased carbon dioxide uptake of phytoplankton. Surface water TP did not linearly correlate with chlorophyll-a concentrations. Obligate and optionally submerged macrophyte species that utilise HCO were separated from CO-only-users by HCO concentrations, with an area under the curve (AUC) of 68% and 70% (both p < .001) between groups. Obligate and optionally submerged macrophyte assemblages only composed of HCO-users and those exclusively composed of CO-only-users showed an even stronger separation based on the HCO concentration, with both an AUC of 82% and 78% (both p < .001). Our results underline that DIC can greatly affect riverine macrophytes. However, absolute concentrations of HCO are less relevant, while the connection to pH is more important, reflecting CO concentrations. River monitoring and management should consider the interaction between nutrients DIC, surface water and sedimental compartment as important factors affecting macrophyte occurrence, rather than solely focussing on surface water nutrients.
氮和磷浓度被广泛认为是驱动河流中大型水生植物组合的因素。然而，可用于植物的溶解无机碳 (DIC) - 以 CO 和 HCO 的形式存在 - 也具有重要意义。基于文献，我们提出了一个关于藻类、大型水生植物、DIC、pH 值、光照、N、P 以及地表水和底泥区之间相互作用的概念模型。通过分析两个独立的数据集 (i) 关于河流理化性质和叶绿素 a，以及 (ii) 关于河流理化性质和大型水生植物，我们量化了这个概念中的三个联系：(1) 叶绿素 a 与 pH 值的相关性，(2) 总磷 (TP) 与叶绿素 a 的相关性，以及 (3) 沿 DIC 梯度的大型水生植物中 HCO 用户和 CO 仅用户的出现。由于浮游植物二氧化碳吸收的增加，叶绿素 a 与 pH 值呈正相关 (R-squared = 77%，p <.001)。地表水 TP 与叶绿素 a 浓度没有线性相关性。利用 HCO 的必需和可选的淹没大型水生植物物种与仅使用 CO 的物种通过 HCO 浓度分离，组间曲线下面积 (AUC) 分别为 68%和 70%（均 p <.001）。仅由 HCO 用户组成的必需和可选的淹没大型水生植物组合以及仅由 CO 仅用户组成的组合，基于 HCO 浓度的分离更为明显，两者的 AUC 分别为 82%和 78%（均 p <.001）。我们的结果强调了 DIC 可以极大地影响河流大型水生植物。然而，HCO 的绝对浓度不太重要，而与 pH 值的连接更为重要，反映了 CO 浓度。河流监测和管理应考虑 DIC、地表水和底泥区之间的相互作用是影响大型水生植物出现的重要因素，而不仅仅是关注地表水营养物质。
