UK Centre for Ecology & Hydrology, Lancaster Environment Centre, Lancaster, LA1 4AP, UK.
UK Centre for Ecology & Hydrology, Lancaster Environment Centre, Lancaster, LA1 4AP, UK.
Sci Total Environ. 2020 Jun 20;722:137837. doi: 10.1016/j.scitotenv.2020.137837. Epub 2020 Mar 12.
The concentration of dissolved organic matter (DOM) in freshwaters is increasing in large areas of the world. In addition to carbon, DOM contains nitrogen and phosphorus and there is growing concern that these organic nutrients may be bioavailable and contribute to eutrophication. However, relatively few studies have assessed the potential for dissolved organic nitrogen (DON) or dissolved organic phosphorus (DOP) compounds to be bioavailable to natural river phytoplankton communities at different locations or times. Temporal and spatial variations in uptake, relative to environmental characteristics were examined at six riverine sites in two contrasting catchments in the UK. This study also examined how the uptake by riverine phytoplankton of four DON and four DOP compounds commonly found in rivers, varied with concentration. Total nitrogen (TN) and phosphorus (TP) concentrations, the proportion of inorganic nutrient species, and nutrient limitation varied temporally and spatially, as did the potential for DON and DOP uptake. All eight of the DOM compounds tested were bioavailable, but to different extents. Organic nutrient use depended on the concentration of the organic compound supplied, with simple compounds (urea and glucose-6-phosphate) supporting algal growth even at very low concentrations. DON use was negatively correlated with the TN and ammonia concentration and DOP use was negatively correlated with soluble reactive phosphorus (SRP) and dissolved organic carbon (DOC) concentration. The evidence indicates that DOM in rivers has been overlooked as a potential source of nutrients to phytoplankton and therefore as an agent of eutrophication.
在世界上的许多地区，淡水溶解有机物质（DOM）的浓度正在增加。DOM 除了含有碳之外，还含有氮和磷，人们越来越担心这些有机养分可能是生物可利用的，并导致富营养化。然而，相对较少的研究评估了不同地点或时间的天然河流浮游植物群落对溶解有机氮（DON）或溶解有机磷（DOP）化合物的潜在生物利用性。本研究还考察了在英国两个对比流域的六个河流水体中，相对于环境特征，吸收的时间和空间变化。本研究还研究了河流中常见的四种 DON 和四种 DOP 化合物被河流水生浮游植物吸收的情况如何随浓度而变化。总氮（TN）和磷（TP）浓度、无机养分种类的比例以及养分限制在时间和空间上均有所不同，DON 和 DOP 的吸收潜力也有所不同。测试的八种 DOM 化合物均具有生物可利用性，但程度不同。有机养分的利用取决于所供应的有机化合物的浓度，即使在非常低的浓度下，简单化合物（尿素和葡萄糖-6-磷酸）也能支持藻类生长。DON 的利用与 TN 和氨浓度呈负相关，DOP 的利用与可溶性反应磷（SRP）和溶解有机碳（DOC）浓度呈负相关。有证据表明，河流中的 DOM 一直被忽视为浮游植物潜在的养分来源，因此也是富营养化的一个因素。
