Variations of Nitrogen and Phosphorus in Seawaters

N and P exist in various chemical forms in the sea waters. Deferent forms of N and P biogeochemical behaviors in the Yellow sea waters were discussed in this work. 

Parameter Sea surface layer Sea bottom layer Average for water column 

Since the 1980s, P concentrations exhibited decreasing trends in the SYS, especially 1983 1989 and 1995 1996 near the ecological threshold essential for diatom growth 0.2 pmol/L (Lin et al., 2005). During our observation period (1997 2005), the decreasing trends of P have been continuous in the SYS (Fig. 3.27). Their annual rates were -0.020 )4mol/(L yr) for the water column. 

As illustrated in Fig. 3.28, the N/P ratios increased at annual rates of 3.02 3.98 yr. The climate coefficients were 0.91 0.94 with a significance level of P 0.01. We noted that the N/P ratios increased from approximately 6 in 1997 to over 16 in 2001. There was an indication that, despite the N/P ratio having rapidly increased, it was still at the Redfield ratio that is suitable for ph doplankton growth (Lin et ah, 2005). Until the most recent years the N/P ratios increased abruptly and the environment of the SYS experienced limitations of P, as noted in (Wang and Jiao, 1999 Lii et ah, 2004 2005). 

The warming of seawater in the SYS during 1997 2004 (Fig. 3.29) is consistent with the increase in the mean air temperature observed throughout northern China (Chen et al., 1998) and the increase in SST found in both the Bohai Sea and the ECS. In the SYS, however, the average temperature of the water column (Tav), the average temperature of the sea surface (SST) and the average temperature of the sea bottom layer (BT) all increased more sharply than the SST of both the Bohai Sea and the ECS. In these seas, the 

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