绿潮硬毛藻分解对天鹅湖水体氮磷水平的影响

为了解绿潮硬毛藻衰亡分解对上覆水体营养水平的影响，以荣成天鹅湖不同湖区的沉积物和暴发的硬毛藻为试材，通过室内模拟研究了藻类分解过程中水体氮磷水平及理化性质的变化，并评价了不同湖区沉积物中氮磷的释放潜力.结果表明:硬毛藻衰亡分解使上覆水体中ρ(TN)和ρ(NH₄+-N)均明显上升，并且前期(0~16 d)上升较快，ρ(TN)和ρ(NH₄+-N)最高分别可达12.40和7.98 mg/L；水体中ρ(TP)和ρ(SRP)表现为前期变化不大，19 d后大幅增加，含量变幅分别为0.02~1.14和0.01~0.40 mg/L.在试验中后期(约16 d后)，不同湖区沉积物处理的水体中ρ(TN)、ρ(NH₄+-N)、ρ(TP)、ρ(SRP)均表现为有沉积物含藻处理>无沉积物含藻处理>有沉积物无藻处理.在藻分解的条件下，不同湖区沉积物的氮磷释放能力存在很大差异，氮释放量的顺序为湖中心>西北部>南部，而磷表现为西北部>湖中心>南部.在硬毛藻绿潮的衰亡阶段，由于初期藻体营养盐的直接释放和后期促进沉积物内源释放的间接影响，水体中ρ(TN)和ρ(TP)均明显增加，进而加重了天鹅湖水体的富营养化水平. 

Effects of the Decomposition of Chaetomorpha sp. on Nitrogen and Phosphorus Levels in Water from Swan Lake

Abstract: Macroalgal blooms, which can dramatically modify nitrogen (N) and phosphorus (P) cycle in water column and sediments, have frequently occurred in coastal areas in recent decades. Rongcheng Swan Lake, a natural coastal lagoon in the eastern Shandong Peninsula in China, has suffered from extensive macroalgal blooms dominated by Chaetomorpha sp. over the past ten years. In the present study, Chaetomorpha sp. and the sediments from different areas of Swan Lake were collected to study the influence of algal decomposition on N and P levels in the overlying water. In addition, the changes of physio-chemical parameters in water were detected during the algal decomposition, and the release potential of N and P from sediments in different lake areas was estimated. The results showed that the concentrations of total nitrogen (TN) and NH₄⁺-N in water increased obviously during the first 16 days due to the decomposition of Chaetomorpha sp., and reached 12.40 mg/L and 7.98 mg/L, respectively. However, the concentrations of total phosphorous (TP) and soluble reactive phosphorous (SRP) changed slightly at the early stage, and increased significantly after 19 days. During the experiment, the concentrations of TP and SRP ranged from 0.02-1.14 mg/L and 0.01-0.40 mg/L, respectively. After 16 days of the incubation experiment, N and P concentrations in water at different sediment treatments both followed the order of:treatment with sediments and algae > treatment with only algae > treatment with only sediments. There were great differences in the release ability of N and P from the sediments among different lake regions. Under the condition of algal decomposition, the order of the release amount of N and P from the sediments was:center > northwest > south and northwest > center > south. During the degradation phase of green tide, the concentrations of TN, NH₄⁺-N, TP and SRP in water all increased significantly due to the nutrient release from the decomposing Chaetomorpha sp. and the indirect effect on promoting nutrient release from the sediments, which aggravated the level of water eutrophication in Swan Lake, China. Therefore, the massive decomposing Chaetomorpha sp. should be salvaged quickly to avoid the deterioration of water quality in Swan Lake.