Microbial decomposition of organic matter in a constructed wetland designed for metal retention

Abstract Metal contaminants threaten water resources and constructed wetlands can retain them using microbial processes that are supported by organic compounds. However, organic compounds also form transient metal complexes. To determine how microbial communities from a constructed wetland vary over time and space in their ability to metabolize different carbon compounds, we studied carbon metabolism from microbial communities in a wetland designed for wastewater metals. We incubated bulrush culms in the wetland and retrieved them and floc monthly from January to September. We measured the richness, composition, and rates of bulrush and floc microbial community's carbon metabolic capacity and environmental variables. The metabolic capability of microbial communities to decompose carbon changed temporally with month explaining and 3.7 times (bulrush community) and 1.4 times (floc community) as much variability in the composition of metabolisms compared with spatial location in the wetland. Bulrush communities had greater capacity to degrade carbohydrates and polymers during early stage, winter decomposition. Floc community metabolism richness decreased by one per month from the cool to warm season. Collectively, this suggests temporal changes in a constructed wetland can influence the capacity of microbial communities to decompose different carbon compounds which has potential implications for organic-metal complexes.