Abstract In eutrophic lakes, macrophytes can improve water quality through their uptake of excess nutrients and by stimulating microorganism activity, particularly for nitrogen (through nitrification and denitrification). However, some adverse effects of macrophytes are of concern, including accumulation of sedimentary organic carbon, decreasing dissolved oxygen concentration, and increasing greenhouse gas emissions. Accordingly, restoration of macrophytes in littoral zones should consider the overall effects of macrophytes on the surrounding environment. Here, the effects of emergent macrophytes on water quality, sedimentary organic carbon characteristics, and greenhouse gas emissions were investigated in a eutrophic lake (Lake Hachiro, Japan). Field surveys were conducted both inside and outside nine emergent macrophyte zones in July and November 2017; the results demonstrated no significant differences in oxygen concentration, sedimentary organic carbon accumulation, or fatty acid biomarker profiles over the surveyed period. This indicates that emergent macrophytes had no detrimental effects on the benthic environment of Lake Hachiro. In addition, significant reduction in nitrate concentration was confirmed in the artificially restored Zizania latifolia community based on a field chamber experiment. This was likely associated with increased microbial activity, as evidenced by the contemporaneous observation of increased emissions of N2O gas (a byproduct of denitrification and nitrification processes) inside the areas with vegetation cover. The N2O gas emissions observed here were considerably lower than those reported previously for wastewater treatment facilities (e.g., constructed wetlands). This study demonstrates that restoring macrophytes did not have a negative influence on the benthic environment in this eutrophic lake. Elucidating the mechanisms underlying this lack of degradation of benthic conditions will help ensure that future restoration of macrophyte cover can be undertaken in the littoral zones of eutrophic lakes without any corresponding detrimental impacts.

中文翻译：

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挺水植物恢复对富营养化湖泊沿岸带底栖环境的影响

摘要 在富营养化湖泊中，大型植物可以通过吸收多余的养分和刺激微生物活动来改善水质，尤其是对氮的活动（通过硝化和反硝化作用）。然而，大型植物的一些不利影响值得关注，包括沉积有机碳的积累、溶解氧浓度的降低和温室气体排放的增加。因此，沿海地区大型植物的恢复应考虑大型植物对周围环境的整体影响。在这里，在富营养化湖泊（日本八郎湖）中研究了挺水植物对水质、沉积有机碳特征和温室气体排放的影响。2017 年 7 月和 11 月，在 9 个大型挺生植物区内外进行了实地调查；结果表明，在调查期间，氧浓度、沉积有机碳积累或脂肪酸生物标志物谱没有显着差异。这表明挺水植物对八郎湖底栖环境没有不利影响。此外，根据田间室内试验，在人工恢复的茼蒿群落中硝酸盐浓度显着降低。这可能与微生物活动增加有关，同时观察到植被覆盖区域内 N2O 气体（反硝化和硝化过程的副产品）排放量增加就证明了这一点。此处观察到的 N2O 气体排放量远低于先前报告的废水处理设施（例如人工湿地）的排放量。这项研究表明，恢复大型植物对这个富营养化湖泊的底栖环境没有负面影响。阐明底栖条件没有退化的潜在机制将有助于确保未来在富营养化湖泊沿岸地区恢复大型植物覆盖，而不会产生任何相应的不利影响。