| 引用本文: | 蔡璐依,张灿,何毓新.云南洱海表层沉积物中C25高支链类异戊烯烃(HBIs)的特征及其生物地球化学指示意义.湖泊科学,2023,35(3):922-933. DOI:10.18307/2023.0312 |
| Cai Luyi,Zhang Can,He Yuxin.Characteristics and biogeochemical implications of C25 highly branched isoprenoids (HBIs) in surface sediments of Lake Erhai in Yunnan Province. J. Lake Sci.2023,35(3):922-933. DOI:10.18307/2023.0312 |
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| 摘要: |
| C25高支链类异戊烯烃（C25HBIs）通常被认为是指示硅藻的生物标志化合物，近年来在长江下游湖泊沉积物中被广泛检出。尽管云南湖泊分布广泛，但尚未有C25HBIs检出的相关报道。本研究通过分析洱海不同湖区表层沉积物，首次指出其存在C25HBIs化合物，并通过分析不同C25HBIs化合物的空间分布特征解析其生物地球化学指示意义。结果显示，洱海表层沉积物中存在C25：1HBI和C25：2HBI化合物，但均未检测到同分异构体。洱海沉积物中C25HBIs浓度为11.18 μg/g （TOC），显著高于富营养化的太湖，与澄湖相当。C25：1HBI浓度表现出南高北低的空间分布特征，而C25：2HBI浓度则相反，因此C25：1HBI可能表征了洱海南部湖区的优势硅藻。在C25：2HBI浓度较低（<0.4 μg/g）的沉积物中，C25：1HBI和C25：2HBI呈现微弱正相关，而部分浅水区域的沉积物则表现出C25：2HBI浓度高（>0.4 μg/g）但C25：1HBI浓度低的现象。不同湖区沉积物中C25HBIs浓度与总有机碳和总氮含量的关系存在差异：1）北部湖区C25：1HBI与TN含量呈负相关，可能表明C25：1HBI生源硅藻受到洱海北部农业活动和氮磷肥大量输入的限制。2）中部湖区C25：1HBI和C25：2HBI浓度均与湖泊富营养化水平呈微弱正相关，但与总有机碳含量不存在相关性，说明C25HBIs的生源硅藻受控因素相对复杂。3）南部湖区C25：1HBI浓度和总有机质含量变化一致，和总氮含量呈较强的正相关关系，而C25：2HBI浓度与湖泊总生产力和富营养化水平的相关性均较弱。综上研究发现，洱海的C25：1HBI浓度可以指示洱海南部湖区的优势硅藻和富营养化程度，这与长江下游湖泊现象不同；C25：2HBI可能有较多来源，除了和C25：1HBI相似来源的硅藻以外，还包含某些适于生存在浅水环境的硅藻，因此C25：2HBI受水文条件控制强烈。 |
| 关键词: 洱海 表层沉积物 高支链类异戊烯烃 硅藻 富营养化 水深 |
| DOI：10.18307/2023.0312 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41877332，42073071和42007401）资助。 |
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| Characteristics and biogeochemical implications of C25 highly branched isoprenoids (HBIs) in surface sediments of Lake Erhai in Yunnan Province |
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Cai Luyi1, Zhang Can2, He Yuxin1
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1.School of Earth Sciences, Zhejiang University, Hangzhou 310027, P. R. China;2.State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
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| Abstract: |
| C25 highly branched isoprenoids (HBIs) are generally regarded as biomarkers signaling diatoms and have been widely detected in lakes in the lower-middle reaches of the Yangtze River recently. The lakes in Yunnan Provinces are rich and diverse in diatoms, whereas the reports on C25HBIs still very limit. In this study, we first detected C25:1HBI and C25:2HBI in sediments of Lake Erhai, and further revealed the potential biogeochemical significance of C25HBIs by comparing the spatial differences of the proxy and other underlying factors such as TOC, TN, water depth, etc. The isomers of both C25:1HBI and C25:2HBI were not detected in all surface sediments in Lake Erhai. The concentration of C25HBIs was 11.18 μg/g(TOC), which was much higher than those in eutrophic Lake Taihu and similar with those in Lake Chenghu. The concentration of C25:1HBI increased from the north to the south in Lake Erhai, while inverse trends for the concentration of C25:2HBI. C25:1HBI in Lake Erhai might come from certain predominant diatoms in the southern lake. In sediments with lower concentration of C25:2HBI (<0.4 μg/g), there existed a weak positive correlation between C25:1HBI concentration and C25:2HBI concentration, while in some shallow areas, the concentration of C25:2HBI was high (>0.4 μg/g) and the concentration of C25:1HBI was low. Besides, the correlation between C25HBIs concentration and TOC/TN displayed distinct spatial differences. In the northern part of Lake Erhai, C25:1HBI-sourced diatoms might be inhibited by a large amount of nitrogen and phosphate fertilizer inputs related to agricultural activities. In the central part of Lake Erhai, the concentration of C25HBIs showed a weak positive correlation with TN, but no correlation with TOC, indicating that the underlying control factors of the C25HBIs-sourced diatoms were relatively complex. In the southern part of Lake Erhai, a strong positive correlation could be observed between C25:1HBI concentration and TN, and between C25:1HBI concentration and TOC. But the correlations between C25:2HBI concentration and TN, and between C25:2HBI concentration and TOC were weak. The presence of C25:1HBI in the southern part of Lake Erhai could track eutrophication conditions, which was different from those observed in the middle and lower reaches of the Yangtze River. Meanwhile, C25:2HBI might be contributed from the diatoms also producing C25:1HBI and other diatoms adapted to live in shallow water, so C25:2HBI was strongly affected by the hydrological conditions. |
| Key words: Lake Erhai surface sediment highly branched isoprenoids diatom eutrophication water depth |
