越冬和复苏时期太湖水体蓝藻群落结构的时空变化

为研究太湖蓝藻在越冬与复苏时期群落结构的时空变化规律,于2008年11月,2009年2月,2009年4月,在太湖富营养化较严重的湖区选取8个采样点 (梅梁湾、竺山湾、贡湖湾、大浦、西太湖、南太湖、湖心和湖湾交汇处),分3层采水样,过滤并提取样品DNA经PCR扩增蓝藻16S rDNA序列,采用T-RFLP(末端标记的限制性酶切片段长度多样性)技术分析蓝藻群落结构和多样性变化。共得到87个不同的T-RFs(末端限制性酶切片段),表明太湖蓝藻具有丰富的基因多样性。T-RF相对丰度和聚类分析结果表明,太湖蓝藻群落结构在垂直空间上相似性较高,相似度 > 50%;在水平空间,与Microcystis spp.对应的信号峰在8个采样点均为最强峰(相对丰度为17.7% 47.5%)。竺山湾蓝藻多样性最低,西太湖最高,但其余采样点间蓝藻群落和Shannon多样性指数没有显著差异(P>0.05)。Microcystis相对丰度与Shannon多样性指数呈显著负相关(皮尔逊相关系数为-0.958)。在时间尺度上,相似性分析(Analysis of similarity,ANOSIM)结果显示太湖蓝藻群落结构存在极显著差异( P<0.01) 。春季复苏时蓝藻多样性最高,秋季衰亡时最低。聚类分析表明样品聚成两大特征类群,秋季衰亡时样品独自聚为1支,而春季复苏期和冬季越冬期样品彼此混杂。

Investigation on spatio-temporal pattern of cyanobacterial community structure by T-RFLP during overwinter and recruitment period in Taihu Lake

In order to explore spatio-temporal pattern of cyanobacterial community structure in the period from pre-overwinter to recruitment in Taihu Lake, water samples of three vertical layers were collected at eight sites (Meiliang Bay, Zhushan Bay, Gonghu Bay, Dapu, Western part of Taihu Lake, Southern part of Taihu Lake, Lake center, and cross area) from autumn 2008 to spring 2009. The total number of T-RFs derived from all those water samples was 87, indicating high genetic diversity of cyanobacteria in Taihu Lake. Based on the relative abundances of T-RFs and cluster analysis, the similarities of different vertical samples were higher than 50%. By comparison, it was found that Microcystis spp. dominated in all sampling sites (relative abundance ranged from 17.7% to 47.5%). The number of T-RFs and cyanobacterial diversity was highest at Zhushan Bay but lowest in the western part of Taihu Lake. However, differences were not apparent among other sites (P > 0.05). Pearson correlation analysis revealed a significant negative correlation (R= -0.958) between relative abundance of Microcystis and Shannon-Weiner index. The result of ANOSIM (Analysis of similarity) indicated that the seasonal variation of cyanobacterial community and diversity were extremely significant (P < 0.01). As to the Shannon-Weiner diversity index, samples derived from recruitment period reached the highest value, while samples at pre-overwintering stage in autumn showed the lowest. Cluster analysis revealed that the samples could be divided into two representative groups: Group I consists of samples collected in autumn, while group II contains the samples collected in spring and winter which were intermingled.