Biological invasions induced phosphorus release from sediments in freshwater ecosystems

Alternanthera philoxeroides, as an aquatic invasive species, has widely distributed in eastern China. The process and mechanism by which phosphorus (P) release from sediments induced by A. philoxeroides decomposition occurring in late autumn or early spring were investigated experimentally. The results showed that as simulating time increased, redox potential and dissolved oxygen at water–sediment interface decreased rapidly, reaching reducing (90 mV) and anoxic (0.754 mg/L) conditions, respectively. As a result, soluble reactive P, dissolved total P and total P concentrations in overlying water all rapidly increased with time from 0.02, 0.06 and 0.08 mg/L to 0.53, 0.75 and 0.98 mg/L on average, respectively. In sediments, the rank order of different P speciation contents changed from Oc-P > Fe-P≈Org-P > Ca-P > Al-P≈Ex-P to Org-P≈Fe-P > Oc-P > Ca-P > Al-P≈Ex-P after the experiment, and Fe-P contributed the most to P release from sediments. These results indicate that Fe-P release from sediments during A. philoxeroides decomposition may be an important factor resulting in algae blooms in the lakes of eastern China.