Tide as Steering Factor in Structuring Archaeal and Bacterial Ammonia-Oxidizing Communities in Mangrove Forest Soils Dominated by Avicennia germinans and Rhizophora mangle

Magalí S Marcos,Rosalinde M Keijzer,Hendrikus J Laanbroek,Anthony D Barboza

doi:10.1007/s00248-017-1091-y

Abstract

Mangrove species are adapted to grow at specific zones in a tidal gradient. Here we tested the hypothesis that the archaeal and bacterial ammonia-oxidizing microbial communities differ in soils dominated by the mangrove species Avicennia germinans and Rhizophora mangle. Two of the sampling locations were tidal locations, while the other location was impounded. Differences in the community compositions of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were analyzed by denaturing gradient gel electrophoresis (DGGE) of amoA genes and by MiSeq 16S rRNA gene-sequencing. The abundances of AOA and AOB were established by quantitative PCR of amoA genes. In addition, we analyzed the total microbial community composition based on 16S rRNA genes and explored the influence of soil physicochemical properties underneath Avicennia germinans and Rhizophora mangle on microbial communities. AOA were always more abundant than AOB, but the effect of mangrove species on total numbers of ammonia oxidizers was location-specific. The microbial communities including the ammonia oxidizers in soils associated with A. germinans and R. mangle differed only at the tidal locations. In conclusion, potential site-specific effects of mangrove species on soil microbial communities including those of the AOA and AOB are apparently overruled by the absence or presence of tide.

Highlights

Mangrove forests are highly valuable ecosystems for the numerous products and fundamental services they provide [1]
The effect of mangrove species on the abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) was studied by quantifying the archaeal and bacterial amoA genes in samples of soils covered with A. germinans and R. mangle
We observed significant effects of mangrove species on AOA gene abundance only in soil samples from PI, where soils covered with R. mangle had almost three orders of magnitude higher gene abundances than soils covered with A. germinans (p < 0.005)

Summary

Introduction

Mangrove forests are highly valuable ecosystems for the numerous products and fundamental services they provide [1] These ecosystems are confined to intertidal coastal areas from (sub)tropical regions, and within these areas they often show zonation patterns, in which monospecific bands of trees are formed parallel to the shoreline [2]. Distinct differences in soil pH values, redox potentials, sulfide, and organic matter concentrations were reported in soils covered with these mangrove trees [6]. These species differ in their tissue chemistry: Rhizophora spp. have higher contents of total soluble phenolics (including tannins) and higher C:N ratios (i.e., lower nutritive value) than

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