Author(s): Cesar Macedo Lima Filho
Institution or organization of origin: Federal University of Rio de Janeiro
Eutrophication is a worldwide water quality issue characterized by enrichment nutrients such as N and P in water bodies. A promising and sustainable way to mitigate eutrophication is the phytoremediation of nutrients by aquatic plants. An interesting option for phytoremediation is the water hyacinth (Pontederia crassipes) which, together with its microbiota, can be used in restoration. In this study, we aimed to test if the nutrient removal efficiency of P. crassipes and the composition of its root microbial community would change over a seasonal cycle. An offshore mesocosm system was constructed in a subtropical region in Brazil, with 5 interconnected polyethylene water tanks (3000 L) arranged in cascade. NPK fertilizer was added weekly in the first mesocosm to simulate a hypereutrophic condition to increase the soluble phosphorus concentration to 400 μg/L. Each tank received 30 plants, the experiment was carried out over four weeks, and physicochemical parameters were measured weekly. In addition, plant roots were harvested weekly to assess the microbial community composition (16S rRNA gene sequencing). As a result, we observed a higher removal efficiency in summer (53% of P, 17% of N) than in winter (23% of P, 4% of N). Furthermore, the composition of the root microbial community changed from summer to winter. The main Orders identified were Chroococcales in summer and Bacillales in winter. Thus, our results suggest that seasonality influences phytoremediation and the root microbiota, which is majorly linked to temperature variation.