Spatiotemporal Patterns and Mechanisms of Periphytic Biofilm-Induced Fe Accumulation in Paddy Fields

A high content of iron (Fe) within paddy ecosystems can poison rice plants or increase the risk of migration from rice fields to pollute adjacent rivers and streams. Here, we found that paddy field periphytic biofilms, ubiquitous microbial aggregates that grow on the soil surface, function as potential in situ biointerceptors via Fe accumulation. This is because periphytic biofilms were discovered, according to a spatiotemporal distribution field survey, to have a high capacity for Fe accumulation. The Fe contents in the paddy field periphytic biofilms ranged from 12.40 to 50.60 g/kg at spatial distribution and from 18.24 to 56.53 g/kg at temporal distribution, revealing significant spatiotemporal patterns consistent with the Fe concentration in soils. Extracellular polymeric substance-dominated abiotic accumulation may be a key mechanism that accounts for no less than 30–46% of the Fe accumulation in periphytic biofilms. Periphytic biofilms that accumulate Fe hold potential in intercepting their migration from paddy soil to adjacent ecosystems, thus alleviating Fe poisoning in rice plants as well as minimizing pollution in the adjoining fields. Our findings suggest that the application of periphytic biofilms is a promising engineering measure for alleviating the negative effects of excessive Fe in paddy fields.