洪泽湖有毒和无毒微囊藻丰度及其与环境因子之间的相关分析

为了解洪泽湖有毒和无毒微囊藻丰度及其空间分布,于2014年8月对洪泽湖30个采样点水体的营养盐浓度和Calson富营养化指数(trophic state index,TSI)进行研究,同时采用实时荧光定量PCR技术测定了有毒和无毒微囊藻丰度.结果表明,洪泽湖水体的总氮和总磷浓度平均值分别为1.63 mg·L-1和0.11 mg·L-1,富营养化指数在58.1~73.6之间,洪泽湖水质呈富营养化状态;有毒微囊藻在洪泽湖广泛分布,其丰度在1.13×104~3.51×106copies·m L-1之间,总微囊藻丰度在1.06×105~1.10×107copies·m L-1之间,有毒微囊藻占总微囊藻的比例在8.5%~38.5%之间,平均值为23.6%,有毒微囊藻丰度及其比例均呈现出明显的空间差异性;相关分析结果显示,总微囊藻、有毒微囊藻和有毒微囊藻所占比例三者之间呈极显著正相关性(P0.01),总微囊藻和有毒微囊藻丰度与叶绿素a浓度和TSI有极显著正相关性(P0.01),与透明度有极显著负相关性(P0.01),有毒微囊藻所占比例与叶绿素a、总氮、总磷和TSI有极显著正相关性(P0.01),与TN/TP和透明度有极显著负相关(P0.01).因此,削减洪泽湖总氮、总磷浓度一方面可以降低水体富营养化水平,另一方面有利于抑制有毒微囊藻对无毒微囊藻的竞争优势.

Abundance of Toxic and Non-toxic Microcystis sp. in Lake Hongze and Its Correlation with Environmental Factors

In the present study, the eutrophic level of 30 water samples collected from Lake hongze in August 2014 were analyzed, and the abundance of toxic and non-toxic Microcystis sp., together with their spatial distribution, was investigated by quantitative real-time PCR techniques. The results showed that the average concentrations of total nitrogen and total phosphorus were 1.63 and 0.11 mg ·L^-1, respectively. The trophic state index (TSI) ranged from 58.1 to 73.6, and the water quality was in the state of eutrophication based on TSI. Toxic Microcystis was widely distributed in Lake Hongze, and its abundance varied sharply, from 1.13×10⁴ to 3.51×10⁶copies ·mL^-1, and the abundance of total Microcystis ranged from 1.06×10⁵ to 1.10×10⁷ copies ·mL^-1, meanwhile, the proportion of toxic Microcystis in the total Microcystis ranged from 8.5% to 38.5%, with the average value of 23.6%. Correlation analysis indicated that there was a significant positive correlation among total Microcystis, toxic Microcystis and the toxic proportion (P < 0.01). The abundance of total and toxic Microcystis was significantly positively correlated to chlorophyll a (Chl-a) concentrations and TSI (P < 0.01), but was negatively correlated to transparency (SD) (P < 0.01). The ratio of toxic Microcystis to total Microcystis was significantly positively correlated to Chl-a, TN, TP and TSI (P < 0.01), but significantly negatively correlated to the ratio of TN to TP and SD (P < 0.01). Therefore, reducing total nitrogen and phosphorus concentrations could not only lower the eutrophication level of Lake Hongze, but also inhibit the competition advantage of the toxic Microcystis over non-toxic Microcystis.