Ecological responses and remediation ability of water fern (Azolla japonica) to water pollution

Abstract

The ability of the water fern Azolla japonica to remediate phosphorus (P), nitrogen (N), and iron (Fe) contamination, and its physiological responses to three common sources of water pollution (landfill leachate, swine lagoon sewage, and fish farm sewage) and standard solution were investigated. The biomass, water content, and chlorophyll content of Azolla japonica in each solution were measured, and the concentrations and accumulation rates of polluting elements in the solutions were determined. A. japonica showed over eight-fold increase in biomass within only 20 d in every solution except in swine lagoon sewage, extremely high in N concentration. Consistent chlorophyll and water contents of the plant in most solutions showed that A. japonica can adapt to highly concentrated solutions. N, P, and Fe concentrations of the solutions decreased significantly within the 20 d. In most treatments, A. japonica showed high N accumulation and also showed total uptake of P and Fe from the solutions. In reference to this result, using this species as a phytoremediator plant would have additional benefits of helping maintaining endangered populations of A. japonica. Therefore, the plant’s fast growth, good element remediation efficiency, and conservation needs makes A. japonica a suitable plant species for pollution remediation.