Abstract
Field and laboratory investigations were conducted to characterize bacterial diversity and community structure in a badly contaminated mangrove wetland adjacent to the metropolitan area of a megacity in subtropical China. Next-generation sequencing technique was used for sequencing the V4–V5 region of the 16s rRNA gene on the Illumina system. Collectively, Proteobacteria, Chloroflexi, Planctomycetes, Actinobacteria and Bacteroidetes were the predominant phyla identified in the investigated soils. A significant spatial variation in bacterial diversity and community structure was observed for the investigated mangrove soils. Heavy metal pollution played a key role in reducing the bacterial diversity. The spatial variation in soil-borne heavy metals shaped the spatial variation in bacterial diversity and community structure in the study area. Other environmental factors such as total carbon and total nitrogen in the soils that are affected by seasonal change in temperature could also influence the bacterial abundance, diversity and community structure though the temporal variation was relatively weaker, as compared to spatial variation. The bacterial diversity index was lower in the investigated site than in the comparable reference site with less contaminated status. The community structure in mangrove soils at the current study site was, to a remarkable extent, different from those in the tropical mangrove wetlands around the world.
Highlights
Mangrove forests are rich, diverse and complex ecosystems that are distributed in tidal zones of tropical and subtropical regions around the world [1,2]
The concentration of both Total carbon (TC) and total nitrogen (TN) was significantly higher in January 2019 than in July 2018, but there was no significant difference in the pH and electrical conductivity (EC)
The current study showed that Cd, Zn, Cu and Pb were the dominant heavy metals at the investigated Futian mangrove soils according to their levels against the thresholds set for Class I
Summary
Mangrove forests are rich, diverse and complex ecosystems that are distributed in tidal zones of tropical and subtropical regions around the world [1,2]. The microorganisms inhabiting mangrove soils play an important role in facilitating the biogeochemical cycling of carbon, sulfur, nitrogen, phosphorus, etc., and promoting plant growth by generating phytohormone and siderophore [5,6]. There have been increasing research interests in microbiomes in mangrove soils by using next-generation sequencing in recent years [6,7]. Available reports showed that the structure of microbial community in mangrove soils tended to change in response to variations in environmental conditions such as vegetation type [8], water salinity and tidal flooding [9], pollution [7,10] and nutrient supply status [11]. Tidal sediments/soils adjacent to metropolitan areas are subject to contamination by heavy metals [12]. It is well established that heavy metal pollution can inhibit microbial activities and
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