Spatial distributions and seasonal variations of particulate phosphorus in the Jiaozhou Bay in North China

Based on the measurements of particulate phosphorus(PP) in the Jiaozhou Bay from May 2003 to April 2004,the spatial distribution,seasonal variation and biogeochemical characteristics of PP were investigated to understand the fates and roles of phosphorus in the Jiaozhou Bay ecosystem.The concentration of the total PP ranged from 0.07 to 2.09 μmol/dm3.The concentration of POP was from 0.01 to 1.83 μmol/dm3,with an average of 0.32 μmol/dm3,which accounted for 49.6% in total PP.The concentration of PIP was from 0.01 to 1.49 μmol/dm3,with an average of 0.33 μmol/dm3,which accounted for 50.4% in total PP.In general,the concentrations of PP in surface water show obvious seasonal variations in the Jiaozhou Bay.POP was the highest in spring,which derived from the accumulation of phyto-detritus and was the lowest in autumn,which was decomposed into seawaters to participate the recycle of phosphorus.PIP was the highest in spring and summer and was the lowest in autumn and winter.PIP was mainly influenced by river input in the inner bay but POP derived from autochthonous source in the outer bay.Overall,the concentrations of PP in the inner bay were higher than those in mouth and the outer bay.In the inner bay,the concentrations of PP with the area near the shore were higher than those in the center of the bay.Totally PP showed the decreasing trend with depth especially in spring and winter.The high value of PP emerged in 20 and 10 m corresponding to summer and autumn,respectively.The changes of POP showed hysteretic effect compared with the changes of Chl a in the investigated year.However,according to the change of Chl a,the second high value of POP which should be emerged in October was missing due to the remineralization of POP and participation in the recycle of phosphorus,which lead to the high concentration of orthophosphate in seawaters.