Influence of macrophytes on phosphorus fractionation in surface sediments in a constructed wetland: Insight from sediment compositions

• Impacts of reed and cattail on phosphorus distributions in sediments were studied in a wetland.
• Sediment compositions i.e. organic matter, alkaline phosphatase, active Al and Fe were analyzed.
• Total phosphorus dominated by inorganic P, mainly Ca-P, was high in open water area and in spring.
• Macrophytes impacted the sediment compositions and then the distributions and mobility of PFs.
• Cattail decreased sediments compositions more than reed and was benefit for P stabilization.

The effect of two widely distributed macrophytes, reed and cattail, on phosphorus fractionations (PFs) of surface sediments distributions from a near-nature constructed wetland were studied in both autumn and spring. The results showed that the average values of PFs in the sediments were ranked in the order of Ca-P > Org-P > Al-P ≈ Fe-P > Ex-P > O-P. The mobile PFs, such as Al-P, Fe-P, Ex-P and Org-P influenced the TP concentrations in macrophytes free area. Only Ca-P was related with TP in macrophytes covered area, indicating the P stability of reed community sediment (RCS) and cattail community sediment (CCS). The other compositions of sediments, i.e. organic matter (OM), alkaline phosphatase activity (APA), and active-Fe were greatly decreased in the presence of macrophytes, while active-Al were slightly increased. OM and active-Al were found to be more significant related with PFs in OWS and RCS, while APA and active-Fe were related with PFs in the macrophytes covered sediments. Therefore, macrophytes induced the variation of sediment compositions and further influenced the distributions and stabilization of PFs. Moreover, cattail community performed better in declining the sediment compositions, P accumulation and its release.