State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences and Carbon Neutral Innovation Research Center, Xiamen University, Xiamen, China.
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences and Carbon Neutral Innovation Research Center, Xiamen University, Xiamen, China.
Environ Res. 2024 Dec 15;263(Pt 1):120049. doi: 10.1016/j.envres.2024.120049. Epub 2024 Sep 23.
Mangrove forests represent important sources of methane, partly thwarting their ecosystem function as an efficient atmospheric carbon dioxide sink. Many studies have focused on the spatial and temporal variability of methane emissions from mangrove ecosystems, yet little is known about the microbial and physical controls on the release of biogenic methane from tidally influenced mangrove sediments. Here, we show that aerobic methane oxidation is a key microbial process that effectively reduces methane emissions from mangrove sediments. We further demonstrate clear links between the tidal cycle and fluctuations in methane fluxes, with contrasting methane emission rates under different tidal amplitudes. Our data suggest that both the microbial methane oxidation activity and pressure-induced advective transport modulated methane fluxes in the mangrove sediments. Methane oxidation activity is limited by the availability of oxygen in the surface sediments, which in turn is controlled by tidal dynamics, further highlighting the interactive physico-biogeochemical controls on biological methane fluxes. Although we found some molecular evidence for anaerobic methanotrophs in the deeper sediments, anaerobic methane oxidation seems to play only a minor role in the mangrove sediments, with potential rates being two orders of magnitude lower than those of aerobic methane oxidation. Our findings confirmed the importance of surface sediments as biological barrier for methane. Specifically, when sediments were exposed to the air, methane consumption increased by ∼227%, and the methane flux was reduced by ∼62%, compared to inundated conditions. Our data demonstrate how tides can orchestrate the daily rhythm of methane consumption and production within mangrove sediments, thus explaining the temporal variability of methane emissions in the tidally influenced coastal mangrove systems.
红树林是甲烷的重要来源，部分阻碍了它们作为高效大气二氧化碳汇的生态系统功能。许多研究都集中在红树林生态系统中甲烷排放的时空变化上，但对于潮汐影响的红树林沉积物中生物成因甲烷释放的微生物和物理控制因素知之甚少。在这里，我们表明好氧甲烷氧化是一种关键的微生物过程，可有效减少红树林沉积物中的甲烷排放。我们进一步证明了潮汐周期与甲烷通量波动之间的明显联系，不同潮差下的甲烷排放速率存在差异。我们的数据表明，潮汐周期和压力诱导的平流输送都会调节红树林沉积物中的甲烷通量，而微生物甲烷氧化活性和压力诱导的平流输送则共同调节了甲烷通量。甲烷氧化活性受到表层沉积物中氧气供应的限制，而氧气供应又受到潮汐动力的控制，这进一步强调了生物甲烷通量的物理-生物地球化学相互作用控制。尽管我们在深层沉积物中发现了一些厌氧甲烷氧化菌的分子证据，但在红树林沉积物中，厌氧甲烷氧化似乎只起次要作用，其潜在速率比好氧甲烷氧化低两个数量级。我们的研究结果证实了表层沉积物作为甲烷生物屏障的重要性。具体来说，当沉积物暴露在空气中时，甲烷消耗增加了约 227%，而甲烷通量减少了约 62%，与淹没条件相比。我们的数据表明，潮汐如何在红树林沉积物中协调甲烷消耗和产生的每日节律，从而解释了潮汐影响的沿海红树林系统中甲烷排放的时间变化。
