Nutrient Element Distributions in the Mesotidal Shuangtaizihe Estuary from North China

J. Zhang, J. Xu, M. Liu, H. Xu, Z. G. Yu, D. Q. Xue


The Shuangtaizihe estuary is characterized by N/P ratios of 102-103, which are likely due to fertilizer applications and sewage discharges in the drainage area. In the estuary, phosphate shows a broad maximum in the mixing zone, presumably due to remobilization from solid phases. Silica and ammonia behave conservatively, although the data are scattered. Nitrate provides a distribution of mixing among three end-members owing to the variabilities of riverine concentrations. A simple mass-balance model was used to estimate the water exchange rate in the Shuangtaizihe estuary, indicating that 45-50% of the effluents in ebb tide returns to the estuary during the following flood tide, the net exchange between the estuary and coastal oceans (i.e. Bohai) is limited to 10% for a tidal period. The Shuangtaizihe estuary acts as a source on the pathway of continental nutrient species to the Northwest Pacific Ocean. The estuary is also a transit zone for bioproduction from phosphate limitation in fresh waters (e.g. river and lake) to nitrogen limitation in coastal oceans.


Nutrient elements; Shuangtaizihe estuary; Bohai; China.

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