Bioswales Presents Significant Microbial Diversity

Overview

Severe weather, especially frequent and heavy precipitation exacerbated by climate change, adds uncertainty to the health of urban environments. A critical concern is the combined sewage overflows (CSOs) due to the city’s old combined sewer systems. One emerging solution is to divert stormwater from entering the sewer system by green infrastructure (GI). GIs are engineering systems which aim to capture and retain street runoff. A typical category of GI in New York City is right-of-way bioswales (ROWB), the standardized small rain gardens that are installed on the right of impermeable urban streets. Another type of GI is the green roof (GR), a shallow layer of soil on the rooftop to retard rainwater from discharging. Besides stormwater management, GIs are capable of urban pollutants degradation and nutrient removal via microbial communities. However, the ecology and function of these microbial communities are yet to be well characterized. The goal of this research is to investigate the microbial structures in the GIs in order to understand how they are shaped by anthropogenic activities. Soil samples collected from 7 ROWBs and 1 GR in Soundview, Bronx were analyzed by targeted amplicon sequencing. Briefly, genomic DNA extracted from the soil were amplified using Earth Microbiome Project recommended 518-806 primer set, which targets the V3-V4 region of the 16S rRNA gene. Purified amplicons were quantified and pooled to make a sequencing library, which was then sequenced by Ion Torrent Personal Genome Machine. Preliminary results show that microbial composition varied significantly across different GI sites and types, and each type of GI has a distinct composition of microbiota. Interestingly, even within the same GI category (ROWB), only 24.4% (957 out of 3924) of operational taxonomic units (OTUs) are shared by both top and base soils. The significant microbial diversity is in accordance with other studies, concluding urban ROWBs are large reservoirs of various functional microbes, which further indicates the multi-functionality of ROWBs. This study further revealed the fact that urban stressors are drivers, instead of inhibitors, of GI microbial diversity, seeding further studies to investigate the role of GIs as decentralized urban stormwater decontamination facilities.