Cawthron Institute, Nelson, New Zealand.
Department of Biological Sciences, University of Waikato, Hamilton, New Zealand.
PLoS One. 2021 Jul 21;16(7):e0254967. doi: 10.1371/journal.pone.0254967. eCollection 2021.
Microcystis is a bloom-forming genus of cyanobacteria with some genotypes that produce highly toxic microcystin hepatotoxins. In waterbodies where biological and physical factors are relatively homogenous, toxin quotas (the average amount of toxin per cell), at a single point in time, are expected to be relatively constant. In this study we challenged this assumption by investigating the spatial distribution of microcystin quotas at a single point in time on two separate occasions in a lake with a major Microcystis bloom. Microcystis cell concentrations varied widely across the lake on both sampling occasions (730- and 137-fold) together with microcystin quotas (148- and 362-fold). Cell concentrations and microcystin quotas were strongly positively correlated (R2 = 0.89, P < 0.001, n = 28; R2 = 0.67, P < 0.001, n = 25). Analysis of Microcystis strains using high-throughput sequencing of the 16S-23S rRNA intergenic spacer region showed no relationship between microcystin quota and the relative abundance of specific sequences. Collectively, the results of this study indicate an association between microcystin production and cell density that magnifies the potential for bloom toxicity at elevated cell concentrations.
微囊藻是一种产毒蓝藻，其部分基因型能够产生具有高肝毒性的微囊藻毒素。在生物和物理因素相对均一的水体中，同一时间点的毒素配额（单位细胞内的毒素平均含量）预计相对稳定。在本研究中，我们通过在一个存在大规模微囊藻水华的湖泊中两次单独时间点上调查微囊藻毒素配额的空间分布，对这一假设提出了挑战。两次采样期间，微囊藻细胞浓度在湖泊中差异很大（730 倍和 137 倍），同时微囊藻毒素配额也存在差异（148 倍和 362 倍）。细胞浓度与微囊藻毒素配额呈显著正相关（R2 = 0.89，P < 0.001，n = 28；R2 = 0.67，P < 0.001，n = 25）。使用 16S-23S rRNA 基因间隔区高通量测序对微囊藻菌株进行分析，未发现微囊藻毒素配额与特定序列相对丰度之间存在关系。综上所述，本研究结果表明，微囊藻毒素的产生与细胞密度之间存在关联，这种关联会放大高细胞浓度下水华毒性的潜在风险。
