| Lake is a major source of methane emissions. Methanogens play a key role in the process of earth biochemical carbon cycle, and it is one of the main factors to produce greenhouse gases. To explore the methanogens in lake sediments could provide biological supports for methane emissions. Based on West Lake(WL) of Hangzhou, the paper has studied the methanogenic community structure and diversity in WL different areas' sediments in winter and summer, using restriction fragment length polymorphism analysis and molecular cloning techniques. And the influences of acquatic macrophytes and the sediment nutrient level on the methanogens were analyzed. The main results are as follows:1?Through analysis of enzyme spectra of methanogenic 16 SrDNA clone library, WL got 38 types of OTU in winter. Sequencing results showed that four methanogenic orders exsisted in WL: M.microbiales?M.sarcinales?M.bacteriales and M.coccales, the former two orders were affiliated with Methanomicrobia, which was dominant in each sublake of WL, and the proportion was approaching to 68%. Seven types of methanogenic family, affiliated with each methanogenic order, were found: M.sarcinaceae?M.caldococacceae?M.regulaceae?M.microbiaceae?M.bacteriaceae?M.thermaceae and M.saetaceae.2?In summer, WL got 21 types of OTU, and three kinds of methanogenic order were detected: M.microbiales?M.sarcinales and M.bacteriales, and the proportion difference of M.microbiales and M.sarcinales,which affilicated to Methanomicrobia, was big; as the advantage, the former was significantly higher than the latter. Five types of methanogenic family were detected: M.microbiaceae?M.bacteriaceae?M.saetaceae?M.regulaceae and M.saricinaceae. M.microbiaceae was still dominant in each sublake, and the proportion of last three ones was less than 15%.3?In winter, the OTU number of methanogenic 16 SrDNA clone library from the west and outer areas sediments were respectively 23, 24. Shannon-Wiener diversity index of the west areas, which could reflect the structure diversity of the methanogenic community, was from 1.978 to 2.323, but the maximum number of outer areas was only 2.002, and most were less than 1.978, and the similar regularity to Simpson diversity index. It could prove the structure diversity of the methanogenic community in the sublakes of west areas was higher than that of outer areas. Besides, the regularity was suitable for the diversity of methanogen, M.caldococaceae and M.sarcinaceae were only found in west areas.4?In winter, the evenness in the sublakes with aquatic macrophyte rehabilitation of west areas was higher than that in the scarce areas, but the regularity of methanogenic diversity was not obvious, the same number of methanogens class exsisted in Maojiabu's rehabilitation and scarce points; the class number of scarce point was one more than the rehabilitation point in Wugui; while the conclusion of the class number between rehabilitation and scarce point in Yuhu was opposite with that in Wugui. Perhaps the acquatic macrophytes' coverage and growth cycle in each sublake were different, combined with background nutrient concentrations of sediments.5?Whether in winter or summer, Methanomicrobia was as an advantage of methanogenic family, which up to 50%. But in winter, the diversity and structure of methanogenic community was higher than that in summer, M.thermaceae and M.caldococcaceae were only detected in winter. Probably most submerged macrophytes were in growing season in summer, the roots secretion of oxygen contributes much to the partial REDOX state in sediments, so that the growth of anaerobic methanogenes was inhibited to some extent. |
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