Phosphorus Release from Sediments in a Riparian <i>Phragmites australis</i> Community at the Estuary of the Chikugogawa River, Western Japan

Abstract

In order to determine the contribution of aquatic macrophyte communities on nutrition to sustain the high primary productivity of an estuary aquatic community, we analyzed the process of phosphorus release from sediments in aquatic macrophyte community in the estuary of the Chikugogawa River, South-Western Japan. Vertical profile of 3 4 PO  concentration and redox potential (Eh) of pore water in sediments were investigated within and outside the Phragmites australis community. Sediment horizon lower than 23 cm layer from the surface showed anaerobic (Eh < −200 mV) in the P. australis community, whereas sediment was constantly oxic (Eh > 0 mV) up to 50 cm depth outside the P. australis community without organic matter accumulation. Non-vegetated sediment with organic matter accumulation showed anoxic profile as vegetated site. concentration in anaerobic parts of sediment showed higher than oxic parts, and higher concentration in sediment pore water corresponded to sulfur deposition in sediment. Sulfate ion supplied from the sea water is reduced under the anoxic condition and S 2− reacts with water-insoluble phosphorus salts e.g. PO  to river water.

Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands

“…Environmental factors e.g., temperature [ 15 ], pH [ 16 ], redox potential [ 17 ], Eh [ 18 ], P concentration gradient [ 19 ] and hydrological conditions [ 20 ] in the sediment–water interface would affect P release processes and release rates [ 21 ]. However, the results from different sediments are sometimes not the same because P release processes and release rates are significantly affected by both the physical and chemical properties of the sediments [ 22 , 23 , 24 , 25 , 26 ].…”