Aix-Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, 13545 Aix-en-Provence, France.
Aix-Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, 13545 Aix-en-Provence, France; Centre for Tropical Water and Aquatic Ecosystem Research, James Cook University, Townsville, Queensland 4811, Australia.
Sci Total Environ. 2018 Nov 15;642:764-780. doi: 10.1016/j.scitotenv.2018.06.095. Epub 2018 Jun 17.
Evaluating the sources of nutrient inputs to coastal lagoons is required to understand the functioning of these ecosystems and their vulnerability to eutrophication. Whereas terrestrial groundwater processes are increasingly recognized as relevant sources of nutrients to coastal lagoons, there are still limited studies evaluating separately nutrient fluxes driven by terrestrial groundwater discharge and lagoon water recirculation through sediments. In this study, we assess the relative significance of these sources in conveying dissolved inorganic nutrients (NO, NH and PO) to a coastal lagoon (La Palme lagoon; France, Mediterranean Sea) using concurrent water and radon mass balances. The recirculation of lagoon water through sediments represents a source of NH (1900-5500 mol d) and PO (22-71 mol d), but acts as a sink of NO. Estimated karstic groundwater-driven inputs of NO, NH and PO to the lagoon are on the order of 200-1200, 1-12 and 1.5-8.7 mol d, respectively. A comparison between the main nutrient sources to the lagoon (karstic groundwater, recirculation, diffusion from sediments, inputs from a sewage treatment plant and atmospheric deposition) reveals that the recirculation of lagoon water through sediments is the main source of both dissolved inorganic nitrogen (DIN) and phosphorous (DIP) to La Palme lagoon. These results are in contrast with several studies conducted in systems influenced by terrestrial groundwater inputs, where groundwater is often assumed to be the main pathway for dissolved inorganic nutrient loads. This work highlights the important role of lagoon water recirculation through permeable sediments as a major conveyor of dissolved nutrients to coastal lagoons and, thus, the need for a sound understanding of the recirculation-driven nutrient fluxes and their ecological implications to sustainably manage lagoonal ecosystems.
评估营养物质输入到沿海泻湖的来源，对于了解这些生态系统的功能及其富营养化的脆弱性至关重要。尽管陆地地下水过程越来越被认为是沿海泻湖营养物质的重要来源，但仍有有限的研究分别评估由陆地地下水排泄和通过沉积物的泻湖水再循环驱动的养分通量。在这项研究中，我们使用同时的水和氡质量平衡来评估这些来源在向沿海泻湖（法国地中海的拉帕尔默泻湖）输送溶解无机养分（NO、NH 和 PO）方面的相对重要性。泻湖水通过沉积物的再循环是 NH（1900-5500 mol d）和 PO（22-71 mol d）的来源，但也是 NO 的汇。估计到泻湖的岩溶地下水驱动的 NO、NH 和 PO 输入量分别为 200-1200、1-12 和 1.5-8.7 mol d。对泻湖主要养分来源（岩溶地下水、再循环、沉积物扩散、污水处理厂输入和大气沉积）的比较表明，泻湖水通过沉积物的再循环是拉帕尔默泻湖溶解无机氮（DIN）和磷（DIP）的主要来源。这些结果与在受陆地地下水输入影响的系统中进行的几项研究形成对比，在这些研究中，地下水通常被认为是溶解无机养分负荷的主要途径。这项工作强调了通过可渗透沉积物再循环泻湖水作为向沿海泻湖输送溶解养分的主要载体的重要作用，因此需要深入了解再循环驱动的养分通量及其对可持续管理泻湖生态系统的生态影响。
