Spatial and Temporal Distribution of Total Phosphorus in Sediments of Shuangtai Estuary Wetland during the Period of Reed Growth

Phosphorus is an essential macronutrient that plays a crucial role in the regulation of the biological productivity and biogeochemical cycling of other biogenic elements. As a large tidal wetland dominated by reeds in Liaoning province, China, the Shuangtai estuary wetland is a unique ecosystem class. To better understand the spatial and temporal distributions of total phosphorus (TP) in the sediments of the Shuangtai estuary wetland during the period of reed growth, eight sampling sites were established within the wetland, approximately 11 to 24 km from Liaohe River. These sites were sampled once a month at multiple sediment depth intervals between April and October in 2018 and 2019, periods of time that corresponded with the reed growth period. An alkali fusion method was used to determine TP in the sediment samples. The results show that sediment TP content of wetland sediments ranged from 0.001 to 0.781 mg/kg, and decreases from southwest to northeast with the increase in sediment depth. The TP content reaches the maximum corresponding to the fastest growth stage of the reeds (June and July), while the minimum occurs in October (i.e., the maturity stage of reeds). The variation law of TP in cross-sectional sediment in the wetland is that the deeper the sediments are, the lower the content; its maximum content occurs in surface soil. The TP content of each site tends to be stable with increasing depth and has a regularly dynamic seasonal variation with the growth of reeds.