## 5 Conclusions  
There was a significant spatial variation in bacterial diversity and community structure in the mangrove soils in the investigated area. Heavy metal pollution generally reduced the bacterial diversity and consequently the spatial variation in soil-borne heavy metals in the investigated area controlled the spatial variation in bacterial diversity and community structure. In addition, 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. In comparison, the bacterial diversity index was lower, as compared to 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. The findings obtained from this study have implications for understanding the biogeochemical processes in the contaminated mangrove wetland for better management of the urban mangrove wetlands. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Study Area**} & **Diversity** & **Community Structure** \\ \cline{2-3}  & **Shannon** & **Five Most Abundant Bacteria (\%) at the** \\  & **Phylum Level** \\ \hline \multirow{2}{*}{Beibu Gulf, China [6]} & \multirow{2}{*}{9.44–10.46} & Proteobacteria (52.3\%), Bacteroidetes (7.73\%), Chloroflexi (6.09\%), Actinobacteria (5.02\%), Parvarchaeota (4.10\%) \\ \hline \multirow{2}{*}{Mai Po Wetland, China [27]} & \multirow{2}{*}{6.94–10.27} & Proteobacteria (45.6\%), Chloroflexi (14.7\%), \\  & & Bacteroidetes (12.0\%), Cyanobacteria (7.6\%), \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Zhangjiang River, China [8]} & \multirow{2}{*}{5.16–5.23} & Proteobacteria, Chloroflexi, Actinobacteria, \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Daya Bay, China [30]} & \multirow{2}{*}{7.90–9.90} & Proteobacteria (55\%), Bacteroidetes (8.1\%), \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Golden Bay, China [31]} & \multirow{2}{*}{8.0–9.0} & Proteobacteria (50\%), Cyanobacteria (11.5\%), \\  & & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Xiamen, China [32]} & \multirow{2}{*}{5.39–9.28} & Proteobacteria, Fusobacteria, \\  & & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Hainan, China [33]} & \multirow{2}{*}{5.10–5.85} & Proteobacteria, Actinobacteria, Chloroflexi, \\  & & & & Acidobacteria, Firmicutes \\ \hline \multirow{2}{*}{Cananeia Estuary, Brazil [34]} & \multirow{2}{*}{6.10–6.30} & Proteobacteria (60\%), Firmicutes (8.1\%), \\  & & & Acidobacteria (6.9\%) Actinobacteria (6.2\%), \\ \hline \multirow{2}{*}{Bengal Bay, India and Bangladesh [35]} & \multirow{2}{*}{NA 1  } & Proteobacteria, Flexibacteria, Actinobacteria, \\  & & & Acidobacteria, Chloroflexi, \\ \hline \multirow{2}{*}{Guayaquil Gulf, Brazil [10]} & \multirow{2}{*}{NA} & Proteobacteria (33.8\%), Firmicutes (25.14\%), \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{Bhitarkanika, India [28]} & \multirow{2}{*}{NA} & Proteobacteria (47.0\%), Actinobacteria (9.8\%), \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{2}{*}{The study} & \multirow{2}{*}{6.45–7.81} & Proteobacteria (41.81\%), Chloroflexi (11.38\%), \\  & & & \\  & & & \\  & & & \\  & & & (6.86\%), Bacteroidetes (4.41\%) \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison of bacterial diversity and community structure in mangrove soils between this study and other reference sites around the world. **Author Contributions:** Conceptualization, S.X. and J.M. ; methodology.J.M., T.Z. ; investigation, J.M., C.X., and D.S. ; resources, S.X. ; data curation, J.M. and T.Z. ; writing--original draft preparation, J.M. ; writing--review and editing, C.L. ; visualization, J.M. and T.Z. ; supervision, S.X. and C.L. ; project administration, S.X. ; funding acquisition, S.X.