滨海湿地甲烷产生途径和产甲烷菌研究进展

Research progresses on methanogenesis pathway and methanogens in coastal wetlands

滨海湿地在全球碳循环中起着重要的作用,其甲烷排放量占全球海洋甲烷排放的75%.本文综述了滨海湿地主要甲烷产生途径、产甲烷菌种类及其影响因子.滨海湿地SO_4^(2-)含量丰富,乙酸发酵和H_2/CO_2途径产甲烷受抑制,乙酸营养型和氢营养型产甲烷菌丰度较低;而利用甲胺类等"非竞争性"底物的C1甲基化合物歧化途径不受硫酸还原菌竞争底物的限制,兼性营养型产甲烷菌成为产甲烷优势菌.盐度与SO_4^(2-)含量和植被类型密切相关,影响竞争性电子和产甲烷底物的种类和含量,对甲烷产生途径和产甲烷菌群落结构有重要影响.目前,滨海湿地产甲烷菌群落结构、甲烷产生途径的关键控制因素尚需明确,其对甲烷排放的影响有待进一步研究.

Coastal wetlands contribute about 75% to the global oceanic CH4 emissions,thus play a vital role in global C cycles. In this paper,we provided a perspective on researches on metabolic,phylogenetic,and ecological diversity of the methanogenic archaea and the regulating environmental factors in coastal wetlands. Because of the presence of more favorable electron acceptors such as sulfate,methanogenesis via CO2 reduction and acetate fermentation are limited by availability of substrates,and hydrogenotrophic and acetotrophic methanogens generally express low relative abundance. In contrast,＂non-competitive＂substrates such as methanol and methylated compounds have been shown to contribute substantially to methane formation in coastal wetlands,and the facultative methanogens are predominant in those environments. Salinity regulates vegetation zonation and is related to SO42- concentration,by regulating types of methanogenic substrates and contents of competitive electron acceptors,indirectly affects the structure and function of methanogens. Major uncertainties in the current studies include the following： methanogen community structure,the key environmental factors regulating methane pathway,and their effects on methane emissions in coastal wetlands.