台灣北部關渡濕地微生物甲烷氧化速率研究

Microbial Methane Oxidation Rates in Guandu Wetland of northern Taiwan

游子慧(Zih-Huei Yu)

指導教授 ： 王珮玲

國立臺灣大學/理學院/海洋研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602970

摘要

微生物甲烷氧化作用在全球甲烷收支扮演重要角色，可分成好氧型及厭氧型兩種。好氧型甲烷氧化作用以氧氣為電子接收者，廣泛分布在土壤表層；而厭氧型甲烷氧化作用 (Anaerobic Oxidation of Methane, AOM) 則可搭配硝酸鹽、氧化錳、氧化鐵、硫酸鹽等氧化態化合物行呼吸作用。濕地的甲烷排放量居全球排放量之冠，但其微生物作用機制及過程，以及消耗甲烷的能力皆未完全釐清，濕地位在氧氣充足的陸域環境中，以往認為以好氧型甲烷氧化作用為主，但近年來研究也開始評估 AOM 在陸域生態系中對甲烷消耗的貢獻，尤其濕地環境有缺氧條件的存在，顯然濕地的 AOM 研究不容忽略。
位於台灣北部之關渡濕地為河岸濕地，受潮汐影響每日有兩次漲、退潮。本研究利用實驗室培養實驗測量好氧與厭氧甲烷氧化速率，採集滿潮及乾潮樣本，在兩種潮位狀態皆進行好氧與厭氧培養實驗，另外也測試添加不同電子接收者對於厭氧甲烷氧化速率的影響。結果顯示乾潮期間好氧甲烷氧化速率大於滿潮期間，其速率差異應與滿潮期間低甲烷濃度使微生物活動力較小有關，而使甲烷氧化速率小於高甲烷濃度的乾潮期間。相反的，厭氧甲烷氧化速率卻是滿潮期間大於乾潮期間，由於關渡濕地位於硫酸鹽充足的半淡鹹水環境，硫酸鹽濃度並非控制 AOM 速率之主因，推測滿潮及乾潮的速率差異可能由於乾潮期間微生物異營作用能競爭過 AOM 而使其速率較小。厭氧甲烷氧化作用添加電子接收者部分，硫酸鹽與無電子接收者組別速率最大，AQDS 組別次之，氧化鐵、檸檬酸鐵、富馬酸組別最小，硝酸鹽及氧化錳組別之速率只出現在部分培養期間。添加實驗結果顯示關渡濕地的厭氧甲烷氧化作用以硫酸鹽為主要的電子接收者，檸檬酸鐵及富馬酸則由於其促進微生物產甲烷作用，因而對甲烷的移除沒有幫助。

關鍵字

濕地 ； 甲烷氧化作用 ； 穩定碳同位素

並列摘要

Microbially-mediated methane oxidation plays an important role in global methane budgets. Aerobic methanotroph uses O2 to serve as an electron acceptor, and is widespread in ground surface. Anaerobic oxidation of methane (AOM) can couple to sulfate reduction, denitrification, iron reduction and manganese reduction, which means that SO42-, NO3-, iron oxide and manganese oxide are able to be the electron acceptors of AOM. Wetlands exist anaerobic conditions and are the largest source of methane emissions, but the AOM mechanisms and their abilities of methane removal have not been fully examined. In this study, a sub-tropical wetland in northern Taiwan, Guandu, was chosen to examine the tidal effects and effects of electron acceptors on microbial methane regulation.
We conducted laboratory experiments with sediments collected during high tide and low tide periods from the Guandu wetland and both aerobic and anaerobic potential methane oxidation rates were estimated. Results showed that aerobic oxidation rates during low tide periods were higher than those during high tide periods. Because the methane concentrations in pore water were higher in low tide sediments than those in high tide sediments, the microbial activities might also be higher during low tides. On the contrary, anaerobic oxidation rates were higher during high tide periods than those during low tide periods. The difference of AOM rates between high tide and low tide periods may be due to microbial competition. Sulfate reduction coupled to organic matter oxidation may outcompete sulfate reduction coupled to methane oxidation, resulting in slow AOM rates during low tide periods.
In electron acceptors addition experiments, the highest potential rates were observed in the sulfate addition and no addition treatments. The AQDS treatment showed lower rates than that in previous two treatments. The AOM rates in the iron oxide, ferric citrate and fumarate treatments were even slower. The AOM was only detected in part of the incubation periods in nitrate and manganese treatments. These results indicated that the major electron acceptor for AOM in the Guandu wetland is sulfate. The addition of two humic acids, ferric citrate and fumarate were not helpful for methane removal, because microbial methane generation was stimulated in much higher rates than those of AOM.

並列關鍵字

wetland ； methane oxidation ； stable carbon isotope

參考文獻

Moran, J.J., House, C.H., Freeman, K.H., Ferry, J.G., 2005. Trace methane oxidation studied in several Euryarchaeota under diverse conditions. Archaea, 1, 303-309.

Amaral, J.A., Knowles, R., 1995. Growth of methanotrophs in methane and oxygen counter gradients. FEMS Microbiology Letters, 126, 215-220.

Anthony, C., 1991. Assimilation of carbon by methylotrophs. Biology of methylotrophs, 79-109.

Armstrong, W., 1979. Aeration in higher plants. InAdvances in Botanic Research; Woolhouse, HW, Ed. Academic Press: London, UK.

Barnes, R., Goldberg, E., 1976. Methane production and consumption in anoxic marine sediments. Geology, 4, 297-300.