Cycling of phosphorus in the Jiaozhou Bay

Dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), particulate inorganic phosphorus (PIP) and particulate organic phosphorus (POP) in the Jiaozhou Bay (JZB) and its adjacent major rivers were analyzed during 2001-2003. DIP was the major form of dissolved phosphorus in JZB, representing 62%-83% of the total dissolved phosphorus (TDP), and the PIP concentration generally exceeded the POP concentration. The concentrations of phosphorus were higher in the north than in the south of the bay, which were related to the fluvial input and water exchange rate. The dissolved phosphorus concentrations were higher in the autumn and spring than in the summer, while the seasonal variation of particulate phosphorus showed opposite pattern. The distribution of phosphorus is mainly affected by the growth of phytoplankton, desorption/adsorption of DIP from and to particulates, and anthropogenic activities. A preliminary phosphorus budget was established. In JZB, riverine input and water exchange flow between JZB and the Huanghai (Yellow) Sea are the major sources of phosphorus, followed by industrial and domestic waste transport, and then atmospheric deposition. Phosphorus burial efficiency is estimated to be 91%. About 52.2×10 ⁶ mol/a of phosphorus were assimilated by phytoplankton, of which about 68% was recycled in the water column and sediment.