微生物和硬毛藻对天鹅湖不同湖区沉积物氮磷释放的影响

Effects of Microbial Activity on Nitrogen and Phosphorus Release from Sediments in Different Lakes of Swan Lake

荣成天鹅湖为一天然瀉湖,近年来绿潮硬毛藻大量爆发,内源污染日益严重。以大型硬毛藻和不同湖区沉积物为试材,设置沉积物+水、沉积物+水(灭菌)、沉积物+水+藻、沉积物+水+藻(灭菌)4个处理,研究了不同微生物活性及藻类条件下上覆水体氮磷质量浓度的变化,同步监测水土界面DO和pH等理化参数,以探讨藻分解和微生物对天鹅湖不同湖区沉积物氮磷释放的影响,为藻华消亡过程中内源污染的治理提供理论依据。结果表明,微生物存在和硬毛藻分解可使水体氮质量浓度明显增加(P<0.05)。试验过程中,水体总氮在有藻和无藻条件下的质量浓度变幅分别为1.56-14.11 mg·L^?1和0.11-8.96 mg·L^?1,后期灭菌处理明显低于未灭菌处理。藻分解对水体磷质量浓度具有极显著影响(P<0.01),有藻条件下灭菌处理总磷质量浓度为0.31-1.27 mg·L^?1,未灭菌处理为0.27-1.41 mg·L^?1;而无藻条件下灭菌和未灭菌处理变幅分别为0.019-0.047 mg·L^?1和0.025-0.078 mg·L^?1。在天鹅湖,不同湖区沉积物氮磷的释放能力存在差异,水体氮质量浓度在有藻和无藻条件下均表现为西北部>湖中心>湖南部,磷质量浓度有藻条件下与氮一致,而无藻条件下则表现为湖中心>西北部>湖南部。湖中心沉积物处理水体营养盐浓度受微生物活性影响较大。3种因素对水体氮磷质量浓度的影响效应表现为:藻类>微生物>沉积物。可见,在藻类大量暴发且微生物活性较高的湖中心及西北部,沉积物氮磷的释放潜力较大,尤其在藻类堆积腐烂时期,应引起足够重视。

Rongcheng Swan Lake is a shallow coastal lagoon.Green tides have occurred worldwide frequently in this lagoon in recent years,which dramatically modify endogenous pollution.In this paper,the Chaetomorpha and sediments from different areas were collected to study the concentration changes of nitrogen and phosphorus in water under different microbial activities and algae conditions in the laboratory.Four treatments were set at each lake area,which included sediment+water,sediment+water(sterilized),sediment+water+algae,sediment+water+algae(sterilized).In addition,the changes of physio-chemical parameters in water were detected.The aim of this paper is to discuss the influence of algal decomposition and microbial activity on the release of nutrients from the sediments,which can provide a theoretical basis for the treatments of internal pollution after algal booms.The results showed that microorganisms and Chaetomorpha decomposition both could increase nitrogen concentration in water significantly(P<0.05).Under the condition with algae,total nitrogen(TN)concentration in water ranged at 1.56?14.11 mg·L^?1,which ranged at 0.02?8.96 mg·L^?1 under the condition without algae.At the late stage,nitrogen concentration in non-sterilized treatments was higher than that in sterilized treatments.The effect of algae decomposition on phosphorus concentration in water was significant(P<0.01).Under the condition with algae,total phosphorus(TP)concentration at sterilized and non-sterilized treatments ranged at 0.31?1.27 mg·L^?1 and 0.27?1.41 mg·L^?1,respectively.While under the condition without algae,which ranged at 0.019?0.047 mg·L^?1 and 0.025?0.078 mg·L^?1,respectively.The release capacity of nitrogen and phosphorus from sediments of different lake areas was different.Under same algae conditions,the order of water nitrogen concentration from different sediment treatments was both northwest>center>south.The order of phosphorus concentration was the same as that of nitrogen concentration under the condition with algae,however the order was center>northwest>south under the condition without algae.The nutrient concentration in water at the treatments with sediments from the central lake were greatly affected by microbial activity.The effects of three factors on nutrient concentration in Swan Lake followed the order of algae>microorganisms>sediments.It can be seen that the release potential of nitrogen and phosphorus from sediments was great in the center and northwest of lake,where a large amount of macroalgae outbreak and microbial activity was high.It should be paid enough attention during the period of algae accumulation and decomposition.