Physiological responses and algae inhibition of Pontederia cordata to simulated eutrophication and acid rain co-pollution

Eutrophication and acid rain are two threats that many water bodies must contend with. Eutrophication and climate change have accelerated widespread outbreaks of cyanobacterial blooms as both have become more severe. Pontederia cordata, a garden ornamental plant, can inhibit some algae growth and remove total nitrogen (TN) and total phosphorus (TP) from the water. In this study, we investigated how simulated acid rain and eutrophication co-pollution affected P. cordata's growth physiology and ability to inhibit algae growth. Under mild eutrophication (2 mg·L−1 TN, 0.4 mg·L−1 TP, and 15 mg·L−1 CODMn) or weak acid rain (pH = 5.0), P. cordata alleviated the degree of cell membrane lipid peroxidation by stabilizing superoxide dismutase (SOD) and catalase (CAT) activities in the leaves, allowing for normal plant growth. Under mild eutrophication and acid rain conditions, cultured P. cordata water samples maintained strong algae inhibition by reducing the Chl a content and SOD activity of Microcystis aeruginosa cells. Compound stress where acid rain was the primary inhibitory factor along with moderate or severe eutrophication inhibited P. cordata growth, which probably reduced the input of algae-inhibiting allelochemicals, thus reducing its ability to inhibit algae. In summary, P. cordata has application potential in mild eutrophic water and acid rain (pH ≥ 4). These findings provide guidance for further research on phytoremediation and algae control in scenarios of compound pollution.