铜绿微囊藻水华对水泥界面磷素动态影响的模拟

摘要

采集太湖梅梁湾水样和底泥样，添加铜绿微囊藻（ Microcystis aeruginosa），模拟水华发生全过程，以揭示藻群动态对水－泥界面磷素变化的影响。培养期间（238 d），铜绿微囊藻一直处于“增殖－悬浮”交替状态。藻体增殖引起上覆水pH值平均升高11％～14％。藻体第1次大量增殖后，水中总磷（ TP ）含量降低90％以上，底泥有机磷（ Or⁃P ）含量明显增加。增殖⁃悬浮交替过程中，水溶性磷（ WP ）在TP中的比例从初始的93％降至11％。相比较而言，Or⁃P含量表现为降低和升高交替变化。水泥两相WP含量在藻体首次增殖后迅速降低，但此后平均回升2�7倍（水中）和1�7倍（底泥）。底泥碱性磷酸酶活性与Or⁃P含量之间呈显著负相关（ P＜0�05），与WP呈极显著正相关（P＜0�01）。可以认为，铜绿微囊藻水华过程中，部分藻体迅速衰败分解后释放数量可观的WP，这在一定程度上维持了藻群增殖－悬浮反复和交替发生。%Water and sediment were sampled from the Meiliang Bay of the Taihu Lake, China, to build up a simulated sediment⁃water system with Microcystis aeruginosa added for simulation of the occurrence of Microcystis aeruginosa bloom, with a view to defining how and to what extent alga bloom contributes to variation of phosphorus in the sediment⁃water in⁃terface. Microcystis aeruginosa in the water column always stayed in a state of alternation of proliferation and suspension during the incubation period (238 days). Proliferation of the algae increased pH in the overlying water by 11%-14%. Af⁃ter the first boom of proliferation of the algae, TP in the water decreased by over 90%, while organic P (Or⁃P) in the sed⁃iment increased substantially. The proportion of water⁃soluble P (WP) in TP decreased from the initial 93% to 11% dur⁃ing the period of alternation of proliferation and suspension, while the content of Or⁃P alternated decreasing and increasing during the period. WP contents in both the water and the sediment dropped rapidly to a very low level during the first boom of proliferation of the algae, but afterwards, the content bounced back on average by 2�7 times in the water and 1�7 times in the sediments. In the sediment, activity of alkaline phosphatase was negatively correlated with Or⁃P content ( P<0�05) and positively correlated with WP content ( P<0�01) . Hence, it is believed that quite a portion of alga cells rapidly decay⁃ed and decomposed during the bloom releasing a considerable amount of WP , which to a certain extent sustained the popu⁃lation of Microcystis aeruginosa in alternation of proliferation and suspension.