Title : Seasonal dynamics and phytoremediation potential of aquatic macrophytes Eichhornia crassipes and Pistia stratiotes in tropical aquaculture wastewater
Abstract:
The rapid expansion of aquaculture has significantly increased fish production worldwide but has also resulted in the generation of large volumes of nutrient- and metal-rich wastewater that can degrade receiving aquatic ecosystems if not properly treated. This study assessed both the baseline seasonal variation in aquaculture wastewater quality and the phytoremediation efficiency of two aquatic macrophytes, Eichhornia crassipes (water hyacinth) and Pistia stratiotes (water lettuce), under tropical dry and wet seasonal conditions. Wastewater and plant samples were collected from aquaculture ponds in Makurdi, Nigeria, and an 18-month controlled experiment (January 2024–September 2025) was conducted using nine concrete ponds (700 L each) with three treatments: control, water hyacinth (100%H), and water lettuce (100%L). Initial analyses revealed pronounced seasonal variation in wastewater quality, with significantly higher concentrations of Ca, Mg, Na, K, turbidity, and biochemical oxygen demand during the dry season, while Fe and pH were elevated in the wet season (p < 0.05). Following phytoremediation, substantial reductions in metals, nutrients, and organic load were observed. During the dry season, metal removal efficiencies ranged from 65–82% for water hyacinth and 60–86% for water lettuce, with slightly lower efficiencies during the wet season. Phosphate and nitrate concentrations declined markedly, while physicochemical parameters improved, including increased dissolved oxygen and reduced turbidity and BOD. Metal accumulation patterns in plant tissues confirmed bioaccumulation as the primary removal mechanism, with higher concentrations recorded in roots than shoots. Overall, the results demonstrate strong seasonal influences on aquaculture wastewater composition and confirm the high phytoremediation potential of E. crassipes and P. stratiotes, supporting their application as cost-effective and environmentally sustainable treatment options for tropical aquaculture systems.
