| Abstract: | To study the contents and distribution of inorganic nutrients in the Bohai Sea of China, two cruise surveys were undertaken
in August (summer) 2000 and January (winter) 2001, respectively. A total of 595 water samples were collected from 91 stations
and five nutrients, i.e., nitrate, nitrite, ammonia, phosphate and silicate, were analyzed for each sample. The results show that the average concentration
of dissolved inorganic nitrogen (DIN) in the Bohai Sea in winter (6.529 μmol L−1) is significantly higher than that in summer (3.717 μmol L−1). The phosphorus concentration in winter (0.660 μmol L−1) is also significantly higher than that in summer (0.329 μmol L−1). Mean silicate concentration in winter (7.858 μmol L−1) is, however, not significantly different from that in summer (7.200 μmol L−1). Nutrients also vary considerably in different areas in Bohai Sea. DIN concentration in the Laizhou Bay (4.444 μmol L−1), for example, is significantly higher than those in the Bohai Bay (2.270 μmol L−1) and Bohai Strait (2.431 μmol L−1), which is caused by the discharge of large amounts of nitrogen into Laizhou Bay via Yellow River. The nutrients show different
vertical distribution patterns. In summer, nutrients in bottom layer are generally richer than those in surface and middle
layers. In winter, however, nutrients are not significantly different in different layers. Compared with historic data, DIN
contents have increased continually since the early 1980 s. Based on atomic ratios of different nutrients, nitrogen is still
the limiting factor for algal growth in the Bohai Sea. |
