Departamento de Biología, Universidad Autónoma de Madrid, Madrid 28049, Spain.
Toxins (Basel). 2013 May 3;5(5):939-57. doi: 10.3390/toxins5050939.
Understanding the annual cycle of Microcystis is essential for managing the blooms of this toxic cyanobacterium. The current work investigated the sedimentation of microcystin-producing Microcystis spp. in three reservoirs from Central Spain during the summer and autumn of 2006 and 2007. We confirmed remarkable settling fluxes during and after blooms ranging 10(6)-10(9) cells m(-2) d(-1), which might represent 0.1%-7.6% of the organic matter settled. A comprehensive analysis of the Valmayor reservoir showed average Microcystis settling rates (0.04 d(-1)) and velocities (0.7 m d(-1)) that resembled toxin settling in the same reservoir and were above most reported elsewhere. M. aeruginosa settling rate was significantly higher than that of M. novacekii and M. flos-aquae. Despite the fact that colony sizes did not differ significantly in their average settling rates, we observed extremely high and low rates in large colonies (>5000 cells) and a greater influence of a drop in temperature on small colonies (<1000 cells). We found a 4-14 fold decrease in microcystin cell quota in settling Microcystis of the Cogotas and Valmayor reservoirs compared with pelagic populations, and the hypothetical causes of this are discussed. Our study provides novel data on Microcystis settling patterns in Mediterranean Europe and highlights the need for including morphological, chemotypical and physiological criteria to address the sedimentation of complex Microcystis populations.
了解微囊藻的年周期变化对于管理这种产毒蓝藻的水华至关重要。本研究于 2006 年和 2007 年夏秋季调查了西班牙中部三个水库中微囊藻产毒株的沉降情况。结果表明，在水华期间和之后，微囊藻的沉降通量非常显著，范围为 10(6)-10(9)个细胞 m(-2) d(-1)，可能占沉降有机物的 0.1%-7.6%。对瓦尔梅约水库的综合分析表明，微囊藻的平均沉降速率（0.04 d(-1)）和沉降速度（0.7 m d(-1)）与同一水库中毒素的沉降相似，高于其他大多数报道的结果。铜绿微囊藻的沉降速率明显高于 novacekii 和 flos-aquae 微囊藻。尽管在平均沉降速率方面，藻落大小没有显著差异，但我们观察到大型藻落（>5000 个细胞）的沉降速率极高和极低，以及温度下降对小型藻落（<1000 个细胞）的影响更大。与浮游种群相比，Cogotas 和瓦尔梅约水库中沉降的微囊藻细胞中的微囊藻毒素细胞配额减少了 4-14 倍，讨论了这种情况的可能原因。本研究提供了地中海欧洲微囊藻沉降模式的新数据，并强调需要包括形态学、化学型和生理学标准来解决复杂微囊藻种群的沉降问题。
