The distribution of external phosphorus (P) in the overlying water, pore water, and sediment under different disturbances were investigated and the transformation between internal P forms was analyzed. The results show that physical disturbances can promote the migration of external P from the overlying water to the sediment. In addition, the enhancement was even higher due to the bioturbation of the combined disturbances. Noticeably, the improvement of the P migration in the control was lowest, compared with the three disturbances. This may be attributed to the penetration of dissolved oxygen. Meanwhile, the physical disturbance reduced the average content of (dissolved organic phosphorus) DIP in the pore water by 12.13% (a mean of 6d and 10d), compared with the control. However the reduction was less than that associated with the bioturbation (38.63%) and the combined disturbance (50.79%), respectively. These three disturbances may promote the formation of Fe/Al-P and Ca-P. The formation of Fe/Al-P and Ca-P was largest under the physical disturbance. However, the algal-available phosphorus (AAP) is reduced due to the physical disturbance, suggesting that physical disturbance may promote the transformation of AAP to occluded Fe/Al-P or Ca-P.
Keywords: distribution; disturbances; external phosphorus; phosphorus transformation; synergy.