Estimating Remineralized Phosphate and Its Remineralization Rate in the Northern East China Sea During Summer 1997: A Snapshot Study Before Three-Gorges Dam Construction

Abstract

The northern East China Sea (a.k.a., "The South Sea") is a dynamic zone in which there have been a variety of effects on the marine ecosystem due to the construction of the Three-Gorges Dam. As the northern East China Sea region is vulnerable to climate forcing and anthropogenic impacts it is important to investigate how the remineralization rate in the northern East China Sea has changed in response to such external forcing. To obtain a baseline for future comparison, we use an historical hydrographic dataset from August 1997. We estimate the amount of remineralized phosphate by decomposing the effects of physical mixing and biogeochemical processes from measurements (temperature, salinity, and phosphate) of the water column. The estimated column inventory of remineralized phosphate ranged from 0.8 to 42.4 mmol P m-2 (mean value of 15.2 ± 12.0 mmol P m-2). Our results suggest that the Tsushima Warm Current was a strong contributor to primary production during the summer 1997 in the study area. The estimated summer (June？August) remineralization rate in the region before construction of the Three-Gorges Dam was 18 ± 14 mmol C m-2 d-1.