Green tides,which have happened frequently in coastal areas and lagoons throughout the world in recent decades,can significantly influence the phosphorus (P) cycle between water and sediments.Rongcheng Swan Lake,a natural lagoon on Shandong Peninsula in China,is blooming massive macroalgae.In order to reveal the effects of the macroalgae bloom on P cycling at the watersediment interface,surface sediments and filamentous macroalgae were collected from the dominant zone of Chaetomorpha spp.in Rongcheng Swan Lake.In the present study,fresh sediments and Chaetomorpha were incubated in the laboratory to study the changes of alkaline phosphatase activity (APA) and P concentrations in water and sediment,and algal biomass and P enrichment amount during the macroalgal growth.In addition,the relationship between APA and P concentrations in water was discussed.The results showed that at the beginning of the experiment (0-3 d),P concentrations in the water were high,and total APA in the water at different treatments without sediments slightly changed,then decreased after the treatments with sediments.After one week,soluble reactive P concentrations in the water reached a low level (ranging from 0-0.06 mg/L),except for the treatment under which P concentration was 2.00 mg/L.The total APA increased in all the treatments,especially for low P treatments (0-0.20 mg/L) without sediments (ranging from 6.02 to 18.32 tμmol/(L· h)),which were much higher than those with sediments at the same P level.Compared with the initial value,the concentrations of different P forms in the sediments decreased,but APA increased at the end of the experiment.Algal biomass varied greatly among different initial P levels in the water,and P enrichment amounts in the algae at the end showed significant positive correlation with initial P levels (P ＜ 0.05).The results indicated that Chaetomorpha could absorb large amounts of P in water during growth,which led to an increase in total APA in water.During the middle period (4-12 d),at low P treatments,particulate APA was the dominant fraction,while at high P treatments soluble APA was relatively high.On the other hand,Chaetomorpha growth resulted in the increase of APA in sediments and P concentration gradient at the sediment-water interface,which could also promote the release of redox-sensitive P and Fe/Mn-bound P in sediments to the overlying water.%为研究水体与沉积物中APA(碱性磷酸酶活性)与磷含量的相互关系,于山东省荣成天鹅湖藻类暴发区采集丝状硬毛藻和表层沉积物,进行室内模拟试验,分析了藻类生长过程中水体和沉积物中APA、磷含量、藻体生物量及磷富集量的动态变化.结果表明:①试验初期(0～3 d),水体中ρ(TP)较高,无沉积物组各处理水体总APA变化不大,有沉积物组有所下降.1周后,除ρ(TP)为2.00 mg/L处理外,其余处理水体ρ(SRP)(SRP为可溶性磷)降至较低水平(0 ～0.06 mg/L);水体总APA增加,其中无沉积物组低磷(0 ～0.20 mg/L)处理下APA变幅为6.02 ～ 18.32 μmol/(L·h),远高于相同初始ρ(TP)的有沉积物处理.②与初始值相比,试验结束时低磷处理沉积物中各形态磷含量下降,APA升高.③不同初始ρ(TP)条件下,藻体生物量相差很大,试验结束时藻体磷富集量与初始ρ(TP)呈显著正相关(P＜0.05).研究显示,硬毛藻生长可大量吸收水体中的磷,从而诱导水体中总APA增加,试验中期(4 ～ 12 d)低磷处理中AP(碱性磷酸酶)以颗粒态为主,而高磷(0.50 ～2.00 mg/L)处理中溶解态APA较高;另一方面,藻类生长使沉积物中APA升高,并加大了水-土界面磷的浓度梯度,从而可促进沉积物中可还原态磷和铁锰结合态磷向上覆水体释放.
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