Nutrient dynamics in pore water of tidal marshes near the Yangtze Estuary and Hangzhou Bay, China

Abstract

Tidal marshes act as a buffer system for nutrients in the pore water and play important roles in controlling the budget of nutrients and pollutants that reach the sea. Spatial and seasonal dynamics of pore water nutrients were surveyed in three tidal marshes (Chongming Island, Hengsha Island, and Fengxian tidal flat) near the Yangtze Estuary and Hangzhou Bay from August 2007 to May 2008. Nutrient variations in pore water closely followed seawater quality in the estuaries, while the average concentration of NH 4? -N, the main form of inorganic nitrogen in pore water, was over two orders of magnitude higher than that in seawater which was dominated by nitrate. NH 4 ? -N export (13.81 lmol m -2 h -1 ) was lower than the import of (NO 3 -?NO 2 -)-N (-24.17 lmol m -2 h -1 ) into sediment over the 1-year period, hence reducing N-eutrophication in coastal waters. The export of SiO 3 2--Si and PO 4 3--P from tidal marshes regulated nutrient level and composition and lifted the ratio beyond potentidal element limitation in the coastal system. Moreover, macrophyte plants (Spartina alterniflora and Phragmites australis) played significant roles in controlling nutrient concentration in pore water and its exchange between marshes and estuaries. Fengxian marsh was characterized by higher nutrient concentrations and fluxes than other marshes in response to the more serious eutrophication in Hangzhou Bay than in the Yangtze Estuary.

Landscape genetic structure of Scirpus mariqueter reveals a putatively adaptive differentiation under strong gene flow in estuaries

“…It is divided into the north branch and the south branch by Chongming Island, and the latter is again divided into the north passage and the south passage by another alluvial island, Changxing Island (Figure ). This complex estuary has resulted in highly heterogeneous habitats with dramatically different salinity, tide, and currents (Kong, He, Ding, & Hu, ; Wang, Li, Zhou, & Gao, ; Xue et al, ; Zhang et al, ; Zheng, Ding, & Hu, ). Temporal and spatial variation in salinity is mainly controlled by the relative importance of river–ocean mixing.…”

“…This complex estuary has resulted in highly heterogeneous habitats with dramatically different salinity, tide, and currents (Kong, He, Ding, & Hu, 2004;Wang, Li, Zhou, & Gao, 2011;Xue et al, 2009;Zhang et al, 2013;Zheng, Ding, & Hu, 2008). Temporal and spatial variation in salinity is mainly controlled by the relative importance of river-ocean mixing.…”

Surface Water and Groundwater Interactions in Salt Marshes and Their Impact on Plant Ecology and Coastal Biogeochemistry

“…Salt marsh groundwater generally has a much higher N/P ratio than the Redfield ratio of 16. As a result, the large nutrient fluxes with high N/P ratios can drive primary productivity and modify the nutrient structure and composition of coastal water (Santos, Chen, et al., 2021; W. W. Wang et al., 2011).…”

Numerical Studies on the Suitable Position of Artificial Upwelling in a Semi-Enclosed Bay

“…And mean N and P removal of Chinese seaweed farming are respectively 60.31 and 7.60 t km −2 year −1 [7]. However, high-density seaweed aquaculture can slow down the water circulation and the renewal of surface water, which lead to regional and regional and temporary nutrient deficiency [8][9][10][11]. To relieve nutrient limitations and promote the production of seaweed, artificial upwelling attracts scientific and policy interest.…”