Evaluation of phosphorus distribution and bioavailability in sediments of a subtropical wetland reserve in southeast China

•The bio-available P concentration in the sediments of the Reserve could not be evaluated by measuring P fractions.•The current researches in the Reserve were more focused on only parts of the reserve. This study covers the whole reserve for the bio-available P and P fractions.•There is high scientific and ecological value in the Reserve, which was listed in the “Asia's important wetlands”, “China's priority protection ecosystem” and “China's important wetlands”. The phosphorus (P) fractions and bioavailable P in the sediments from the Quanzhou Bay Estuarine Wetland Nature Reserve were investigated using chemical extraction methods for the first time to study the distribution and bioavailability of P in the reserve sediments. A hypothesis was presented suggesting that the bioavailable P in the sediments could be evaluated using the P fractions. The total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), non-apatite phosphorus (NAIP), and apatite phosphorus (AP) contents in the sediments were in the ranges of 303.87–761.59mgkg−1, 201.22–577.66mgkg−1, 75.83–179.16mgkg−1, 28.86–277.90mgkg−1, and 127.36–289.94mgkg−1, respectively. The water soluble phosphorus (WSP), readily desorbable phosphorus (RDP), algal available phosphorus (AAP), and NaHCO3 extractable phosphorus (Olsen-P) contents in the sediments were in the ranges of 0.58–357.17mgkg−1, 80.77–586.75mgkg−1, 1.09–24.12mgkg−1, and 54.96–676.82mgkg−1, respectively. The correlation analysis results showed that the NAIP was the major component of the bioavailable P and that the impact of the AP on the bioavailable phosphorus may be minimal. Due to the low TP content in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve, the potential pollution risks of P in the sediments may not be very high. The results also show that the bioavailable P concentrations in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve could not be evaluated by measuring the P fractions and that the hypothesis was untenable.