华南热带水库拟柱孢藻产毒基因型的低优势及影响因子分析——以珠海市水库为例

LOW DOMINANCE OF TOXIC GENOTYPE WITHIN THE CYLINDROSPERMOPSIS RACIBORSKII POPULATION AND ITS AFFECTING FACTORS IN TROPICAL RESERVOIRS OF SOUTHERN CHINA- A CASE STUDY OF ZHUHAI CITY

  • 摘要: 研究以珠海市20座水库两次(2018年和2022年)调查数据为基础, 分析华南热带地区产毒拟柱孢藻的发生规律和拟柱孢藻毒素(CYN)的健康风险。基于rpoC1cyrJ基因的荧光定量PCR分析发现, 在两次采样的40个样品中均检到拟柱孢藻, 在其中的33个样品中检到产毒拟柱孢藻。种群内产毒基因型的比例在0.046%—38.66%, 表明产毒株广泛存在但不占优势。与2018年相比, 20座水库的总拟柱孢藻丰度均值在2022年增加近10倍, 但两年的产毒拟柱孢藻丰度无显著差异; 产毒基因型的比例明显下降, 比例均值和最大值分别从2018年的14.86%和38.66%降至2022年的4.17%和17.24%; CYN浓度与产毒细胞比例具有类似的变化趋势, 平均浓度也从0.56 降至0.19 μg/L。线性混合效应模型分析表明, 非产毒基因型丰度随无机磷的升高及硝氮的下降而显著增加, 而产毒拟柱孢藻比例随水温升高而增加。

     

    Abstract: Cylindrospermopsis raciborskii is a species of tropical cyanobacterial that can be found in natural water bodies. It has both toxic and non-toxic, and the coexistence of these genotypes is common. The production of cylindrospermopsin (CYN) is a significant concern due to its high toxicity to humans, and thus investigation on the distribution its toxic strain and the potential affecting factors will help to reduce the toxic risk of C. raciborskii blooms. Based on two surveys (2018 and 2022) in 20 reservoirs in Zhuhai City in tropical southern China, we tried to understand the occurrence of toxic C. raciborskii and assess the health risk of CYN. During the two investigated periods, C. raciborskii and its toxic genotype were detected in all 40 samples by using rpoC1-based qPCR analysis and in 33 samples with cyrJ-based qPCR. The ratios of toxic genotype accounted for 0.046%—38.66% of the total C. raciborskii abundances, indicating that toxic C. raciborskii was widely distributed in Zhuhai reservoirs but had low dominance in the C. raciborskii population. Compared with the year 2018, the averaged abundance of C. raciborskii in the 20 reservoirs increased nearly 10 times in 2022, however there was no significant difference in abundances between the two years. There was a significant reduction in the ratio of toxin-producing genotypes in the population. Both the mean and maximum ratios decreased in 2022 compared to 2018, with the mean ratio declining from 14.86% to 4.17%, and the maximum ratio decreasing from 38.66% to 17.24%. The concentrations of CYN changed with a similar decreasing pattern, with the mean concentration reducing from 0.56 to 0.19 μg/L. Mixed Effect Model showed that elevated PO4-P and decreased NO3-N may favor the growth of non-toxic C. raciborskii, and the ratios of toxic C. raciborskii increased with water temperature.

     

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