Seasonal dynamics of ammonia/ammonium-oxidizing prokaryotes in oxic and anoxic wetland sediments of subtropical coastal mangrove

Yong-Feng Wang,Xiaojun Ma,Yao-Yu Feng,Ji-Dong Gu

doi:10.1007/s00253-012-4510-5

Abstract

Mangrove wetlands are an important ecosystem in tropical and subtropical regions, and the sediments may contain both oxic and anoxic zones. In this study, ammonia/ammonium-oxidizing prokaryotes (AOPs) in yellow and black sediments with vegetation and non-vegetated sediments in a mangrove wetland of subtropical Hong Kong were investigated in winter and summer. The phylogenetic diversity of anammox bacterial 16S rRNA genes and archaeal and bacterial amoA genes (encoding ammonia monooxygenase alpha-subunit) were analyzed using PCR amplification and denaturing gradient gel electrophoresis to reveal their community structures. Quantitative PCR was also used to detect their gene abundances. The results showed that seasonality had little effect, but sediment type had a noticeable influence on the community structures and abundances of anammox bacteria. For ammonia-oxidizing archaea (AOA), seasonality had a small effect on their community structures, but a significant effect on their abundances: AOA amoA genes were significantly higher in winter than in summer. In winter, the vegetated yellow sediments had lower AOA amoA genes than the other types of sediments, but in summer, the vegetated yellow sediments had higher AOA amoA genes than the other types of sediments. Sediment type had no apparent effect on AOA community structures in winter. In summer, however, the vegetated yellow sediments showed obviously different AOA community structures from the other types of sediments. For ammonia-oxidizing bacteria (AOB), seasonality had a significant effect on their community structures and abundances: AOB amoA genes in winter were apparently higher than in summer, and AOB community structures were different between winter and summer. Sediment type had little effect on AOB community structures, but had a noticeable effect on the abundances: AOB amoA genes of the vegetated yellow sediments were obviously lower than the black ones in both seasons. This study has demonstrated that seasonality and sediment type affected community structures and abundances of AOPs differently in oxic and anoxic sediments of the mangrove wetland.

Highlights

This study has demonstrated that seasonality and sediment type affected community structures and abundances of ammonium-oxidizing prokaryotes (AOPs) differently in oxic and anoxic sediments of the mangrove wetland
Ammonia/ammonium-oxidizing prokaryotes (AOPs), including anaerobic ammonium-oxidizing bacteria and aerobic ammonia-oxidizing archaea (AOA) and bacteria (AOB), are three groups of microorganisms that are responsible for ammonium/ammonia oxidation in the global nitrogen cycle
We investigated AOP communities in the rhizosphere and the non-vegetated sediments in a young mangrove wetland, which showed that the roots of young mangrove trees had little influence on the community structures of AOPs (Wang and Gu 2012a, b)

Summary

Introduction

Ammonia/ammonium-oxidizing prokaryotes (AOPs), including anaerobic ammonium-oxidizing (anammox) bacteria and aerobic ammonia-oxidizing archaea (AOA) and bacteria (AOB), are three groups of microorganisms that are responsible for ammonium/ammonia oxidation in the global nitrogen cycle. In addition to their application in inorganic N removal of sewage treatment (Kartal et al 2010), anammox bacteria have been demonstrated to exist in marine environments, including marine water column and sediments (Dang et al 2010; Hong et al 2011; Kuypers et al 2003, 2005; Lam et al 2009), coastal and estuary sediments (Dale et al 2009; Li et al 2011c), coastal mangrove wetlands (Cao et al 2011a; Li et al 2011b, c), and even polar marine sediments and sea ice (Rysgaard and Glud 2004). Functional genes encoding hydrazine oxidoreductase (hzo), nitrite reductase (nir), and hydrazine synthase (hzs) have been used to detect anammox bacteria in natural environments (Harhangi et al 2012; Li et al 2010b; Schmid et al 2008), but the more widely used molecular biomarker remains to be the 16S rRNA gene, currently

Methods

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Conclusion