Abstract:

The hydrology and topography of the lake's estuarine region are intricate, with nutrients such as carbon and nitrogen deposited alongside solid particles, thereby creating diverse habitats for benthic organisms. This study aimed to investigate the prokaryotic community and functional characteristics associated with varying nutrient gradients within estuaries. Specifically, we examined surface sediments of the Raohe River estuary, focusing on the community structure and extracellular enzyme activity of prokaryotes in different nutrient environments using high-throughput sequencing technology. The results revealed that the alpha diversity of prokaryotes was constrained by sediment nutrient content, whereas neither the Shannon index nor Simpson index showed significant differences across sediments with varying nutrient compositions. Conversely, the beta diversity of prokaryotes was significantly influenced by sediment nutrient levels, with community composition exhibiting greater similarity in high-nutrient environments (SOC>15 g·kg⁻¹). Notably, beta diversity was significantly elevated under medium (SOC 10‒15 g·kg⁻¹) and low-nutrient conditions (SOC<10 g·kg⁻¹) (p<0.05). Among the dominant archaeal and bacterial genera, Methanosaeta, Candidatus_ Methanomethylicus, MBNT15, SC-I-84, and Anaeromyxobacter were highly enriched because of the positive influence of key nutrients (SOC, TN, TP, and NH₄⁺-N). In contrast, the relative abundances of Candidatus_Nitrosotenuis and Latescibacterota were negatively affected by the nutrient levels and were primarily enriched in low-nutrient environments (p<0.05). Furthermore, β-glucosidase, acid phosphatase, urease, leucine aminopeptidase, and nitrite reductase were significantly and positively correlated with SOC, TN, TP, and NH₄⁺-N, indicating elevated enzymatic activity in high-nutrient environments. Conversely, peroxidase activity was negatively affected by sediment nutrients and was more pronounced in low-nutrient environments (p<0.05). This study provides a comprehensive analysis of the effects of sediment nutrient variation on the structure and function of prokaryotic communities, underscoring the importance of estuarine sediments with differing nutrient content in maintaining prokaryotic habitats and functional diversity within aquatic ecosystems. Therefore, future research should focus on the potential impacts of sediment changes in solid particles on estuarine ecological environments.

Key words: estuary, sediment, nutrient contents, prokaryotes, extracellular enzyme activity

摘要：

入湖河口区域水文和地形环境复杂，碳、氮等营养物质伴随固体颗粒物在不同区域差异化沉积，为底栖生物提供了多样生境。以饶河入湖河口表层沉积物为研究对象，通过高通量测序技术探究不同养分环境下原核生物群落结构及其胞外酶活性特征。结果表明，沉积物养分含量主要影响原核生物群落的Beta多样性而不是Alpha多样性，高营养环境下（SOC>15 g·kg⁻¹）原核生物群落组成更加接近，其Beta多样性显著高于中营养（SOC 10－15 g·kg⁻¹）和低营养环境（SOC<10 g·kg⁻¹）（p<0.05）。对于优势（Top10）古菌和细菌属，发现Methanosaeta、Candidatus_Methanomethylicus、MBNT15、SC-I-84和Anaeromyxobacter受主要养分（SOC、TN、TP和NH₄⁺-N）的正向影响，在高营养环境下大量富集；而Candidatus_Nitrosotenuis和Latescibacterota则相反（p<0.05）。同时发现，β-葡萄糖苷酶、酸性磷酸酶、脲酶、亮氨酸氨基肽酶和亚硝酸还原酶与SOC、TN、TP和NH₄⁺-N均呈显著正相关关系，在高营养环境下表现出更高的酶活性；而过氧化物酶则相反，在低营养环境下活性更强（p<0.05）。该研究深入分析了沉积物养分变化对原核生物群落结构与功能的影响，强调了具有不同养分含量的入湖河口沉积物对于维持水生态系统原核生物生境和功能多样性至关重要。

关键词: 入湖河口, 沉积物, 养分含量, 原核生物, 胞外酶活性