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Abstract: During both the spring- and the neap-tide periods of November 2005, quasi-simultaneous observations were carried out by six boats over 26 h at 12 stations in the Changjiang (Yangtze River) plume. The simultaneous observations provided the actual distribution isopleths of salinity and nutrients that displayed considerable intra-tidal variations at surface, especially in the southeastern section of the study area. The lack of synopticity in sampling might lead to large discrepancies of the interpolated contours of salinity from the actual distribution isopleths. No clear flood-ebb asymmetry of salinity stratification was observed; whereas at inner stations, surface-to-bottom bulk velocity difference (current layering) always tended to be greater during the ebb fraction of a semidiurnal cycle. At a given station, the weaker neap tides commonly induced stronger salinity stratification, less intra-tidal variability of salinity and nutrients, and less intrusion of bottom saltwater. Nutrients (SiO3 2−, NO3 −, and PO4 3−) showed more nonconservative behaviors during the neap tides, presumably as a result of the prolonged residence time of seawater and decreased suspended particulate matter levels than during the spring tides. [Copyright &y& Elsevier]

Abstract: During four surveys at spring and neap tides in July and November 2005, continuous observations were conducted at four stations adjacent to the Changjiang (Yangtze River) mouth. The observation times lasted for 26h that covered two consecutive semidiurnal cycles. Resuspension events and subsequently enhancements of suspended particulate matter (SPM) were commonly observed within a tidal cycle. Although nutrients (SiO3 2−, NO3 −, and PO4 3−) were primarily governed by salinity, their statistically significant correlations with SPM could always be extracted after partial correlation analysis. Three parameter (salinity, SPM, nutrients) regressions generally produced better results of simulating nutrient concentrations than two parameter (salinity and nutrients) regressions, although compared to the latter, the former R 2 values were elevated by no more than 13%. The partial correlation between SPM and a specific nutrient could be either positive or negative in different surveys, suggesting SPM influenced the nutrients in different ways under various conditions. The minor (albeit statistically significant) impacts of highly dynamic SPM on nutrients might be ascribed to the short duration time of resuspension events and estuarine mixing process, together with the complex nature of circulation in the Changjiang plume seawater. [Copyright &y& Elsevier]