3, respectively. Salinity distribution in the ECS indicates that the discharge of freshwater from the Changjiang River is located in the northeastern part of the study area. Several Daporinad salinity fronts can be easily identified in the inner shelf and midshelf. The first front (salinity between <28 and >28), identified as the inner shelf front, appeared in the surface waters approximately 30–40 km offshore. The second front (salinity between 30

and 31), called the main front, was observed in the surface waters approximately 50–100 km offshore between stations 28–29, 17–18, and 30–31, respectively. This major front represents the boundary between the CDW and the midshelf water (e.g. the TCWW and the mixing water between the YSW and the TCWW). Across this front, hydrographic characteristics showed dramatic changes, with salinity increasing from about 29 to 31 ( Fig. 3A)

and with nitrate concentration decreasing from about 3–6 μM to around the detection limit (∼0.1 μM) ( Fig. 3B). Surface Chl-a also dramatically changed across this front, decreasing by a factor of 1.5–10 from about 3–10 mg m−3 to 0.5–1.0 mg m−3. The third front (salinity SD-208 solubility dmso between 32 and 33), identified as the midshelf front, was located in the surface waters approximately 80–250 km offshore with salinity increasing from 32 to 33. These salinity fronts

are mainly caused by a combination of freshwater discharge of the Changjiang River and forcing by northeasterly winds, as the observed wind direction during the sampling time in spring in the ECS was mainly from the northeast. In spring, the north-northeastern monsoon Interleukin-2 receptor inhibits the northward excursion of the main plume of the Changjiang fresh water and forces the fresh plume to extend southwestward as a narrow band hugging the China coastline. Analogous hydrographic fronts in the ECS have been reported in the recent literature (Belkin et al., 2009 and Chen, 2009). Distributions of nitrate and Chl-a concentrations along three transects mirrored the salinity distribution in the ECS ( Fig. 3A–C). The observed dramatic changes of nitrate and Chl-a concentrations were correlated to hydrographic fronts at the three transects, even though the exact distributions of Chl-a concentrations and plankton biomass in the whole ECS may not totally coincide with hydrographic fronts ( Fig. 2C and D). Our results suggest that the variations in nitrate concentration are likely controlled by hydrography, while marine organism distributions in the study area (manifested in Chl-a and zooplankton) are more patchy and variable.