Ecosystem Changes in the Northern South China Sea - Earth Science: New Methods and Studies - page 161

Figure 9. Variation trends of seawater temperature in the nSCS during 1976-2004. (a), (b), and (c)
show the annual mean of the sea surface temperature (SST), the water column average temperature
in the upper 200 m (Tav), and the temperature at the depth of 200 m (T200). The lines are the linear
regressions.
Nutrient Limitation
Since 1998, DIN concentrations have exhibited a pronounced increasing trend, and
therefore the key nutrient concentration and ratio can be divided into two phases, that
is. before and after 1997 (Table 3). In the first phase, the average DIN concentration
was very low, SSDIN and DIN av were 1.83 and 4.22 μmol l −1 , respectively, which were
lower than the low limit of suitable N concentration for diatom growth (5.71 μmol l −1 ,