Active Methanotrophs and Their Response to Temperature in Marine Environments: An Experimental Study

Jing Li,Xiaoqing Xu,Nengyou Wu,Changling Liu,Xingliang He,Zhilei Sun,Ye Chen

doi:10.3390/jmse9111261

Abstract

Aerobic methane (CH4) oxidation plays a significant role in marine CH4 consumption. Temperature changes resulting from, for example, global warming, have been suggested to be able to influence methanotrophic communities and their CH4 oxidation capacity. However, exact knowledge regarding temperature controls on marine aerobic methane oxidation is still missing. In this study, CH4 consumption and the methanotrophic community structure were investigated by incubating sediments from shallow (Bohai Bay) and deep marine environments (East China Sea) at 4, 15, and 28 °C for up to 250 days. The results show that the abundance of the methanotrophic population, dominated by the family Methylococcaceae (type I methanotrophs), was significantly elevated after all incubations and that aerobic methane oxidation for both areas had a strong temperature sensitivity. A positive correlation between the CH4 oxidation rate and temperature was witnessed in the Bohai Bay incubations, whereas for the East China Sea incubations, the optimum temperature was 15 °C. The systematic variations of pmoA OTUs between the Bohai Bay and East China Sea incubations indicated that the exact behaviors of CH4 oxidation rates with temperature are related to the different methanotrophic community structures in shallow and deep seas. These results are of great significance for quantitatively evaluating the biodegradability of CH4 in different marine environments.

Highlights

At present, gas hydrates are the most abundant source of methane on the earth [1,2,3].A great amount of methane is released due to the decomposition of gas hydrates from submarine reservoirs [4], which are gradually consumed by anaerobic methanotrophic archaea (ANME) in anoxic sediment layers and aerobic methanotrophs in oxic layers [5,6].Methanotrophs are a subset of methylotrophs that utilize CH4 and other C1 compounds as the sole carbon and energy sources under aerobic conditions [7,8]
The CH4 oxidation rates obtained by linear regression analysis show that the CH4 oxidation rates at 4 ◦ C in both areas were lower than those at high temperatures (Table 2 and Table S2)
We investigated the effect of temperature on aerobic methane oxidation and methanotrophic communities using marine sediments collected from Bohai Bay (BB) and East China Sea (ECS)

Summary

Introduction

Gas hydrates are the most abundant source of methane on the earth [1,2,3].A great amount of methane is released due to the decomposition of gas hydrates from submarine reservoirs [4], which are gradually consumed by anaerobic methanotrophic archaea (ANME) in anoxic sediment layers and aerobic methanotrophs in oxic layers [5,6].Methanotrophs are a subset of methylotrophs that utilize CH4 and other C1 compounds as the sole carbon and energy sources under aerobic conditions [7,8]. Aerobic methane oxidation in natural ecosystems is, one important way to control CH4 emissions in the atmosphere, reducing the potential of global warming [9,10,11,12]. Better knowledge on the aerobic methane oxidation of natural ecosystems is of great significance to precisely characterize the emissions of CH4 and trends of global warming. The optimum temperature of aerobic methane oxidation for most ecosystems is between 20–45 ◦ C [7], whereas methanotrophs from acid soils in the Arctic had optimum growth temperatures of less than 10 ◦ C [6]. The lower temperature limits for aerobic methane oxidation in nature are different. Mohanty et al [17]

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