# Flood‐Driven Microbial Resurgence: Functional Shifts and Beneficial Taxa in Post‐Flood Agricultural and Residential Soils in Bangladesh

## TL;DR

The 2024 Bangladesh floods increased soil microbial diversity and introduced beneficial microbes that aid soil recovery and agricultural resilience.

## Contribution

The study identifies 29 beneficial flood-introduced microbes and highlights their functional roles in post-flood soil recovery.

## Key findings

- Flooded soils showed higher microbial diversity and shared 45 species compared to 6 in non-flooded soils.
- Residential soils were enriched with nitrogen-fixing microbes, while agricultural soils had more phosphate solubilizers.
- Unique flood-adapted microbes like Sulfuricurvum sp. and Nitrospira were found in flooded soils.

## Abstract

Flooding events alter microbial communities, impacting soil health and ecosystem recovery. This study examined the 2024 Bangladesh floods' effects on microbial diversity in agricultural and residential soils. We collected paired soil samples from six flooded and two non‐flooded sites within a single rural subdistrict after the floods. This sample size was logistically feasible for an initial survey and provides a foundational data set for future larger‐scale investigations. Our findings revealed that flooding increased microbial diversity and facilitated the dispersal of unique taxa, with 45 species shared between flooded groups compared to only 6 in non‐flooded controls. Notably, 29 beneficial microbes introduced post‐flood were identified, categorized into 8 functional groups critical for soil recovery. Residential soils were enriched in nitrogen‐fixing microbes, whereas agricultural soils showed higher abundance of phosphate solubilizers and plant growth‐promoting rhizobacteria. Sulfur/iron cyclers and cyanobacteria demonstrated flood‐adaptive roles. Pathogen screening identified no canonical human pathogens with the exception of Clostridium disporicum, detected only in one non‐flooded sample. Archaea from Woesearchaeales and bacteria from the Gemmataceae dominated the microbial communities. Flooded environments harbored unique taxa, such as Sulfuricurvum sp. and the Nitrospira genus, which were absent in controls. Alpha diversity analysis revealed a higher Chao1 richness in flooded soils compared to controls, although statistical significance was not found due to insufficient sample size. Beta diversity showed greater variability between flooded soils relative to non‐flooded controls, also not statistically significant. These findings demonstrate that flooding can act as a driver for dispersing beneficial microbes, supporting soil restoration and enhancing agricultural resilience.

Flooding in Bangladesh increased microbial diversity and introduced 29 beneficial taxa, including nitrogen fixers and phosphate solubilizers, enhancing soil recovery. Unique flood‐adapted microbes like Sulfuricurvum sp. emerged, highlighting flooding's role in reshaping microbial communities for agricultural resilience.