Laboratoire Eau Environnement Systèmes Urbains, Université Paris-Est, UMR MA-102, Ecole des Ponts ParisTech, Marne-la-Vallée, France.
ISME J. 2011 Apr;5(4):580-9. doi: 10.1038/ismej.2010.154. Epub 2010 Nov 18.
The vertical and horizontal distribution of the cyanobacterium, Planktothrix rubescens, was studied in a deep alpine lake (Lac du Bourget) in a 2-year monitoring program with 11 sampling points, and a 24-h survey at one sampling station. This species is known to proliferate in the metalimnic layer of numerous deep mesotrophic lakes in temperate areas, and also to produce hepatotoxins. When looking at the distribution of P. rubescens at the scale of the entire lake, we found large variations (up to 10 m) in the depth of the biomass peak in the water column. These variations were closely correlated to isotherm displacements. We also found significant variations in the distribution of the cyanobacterial biomass in the northern and southern parts of the lake. We used a physical modeling approach to demonstrate that two internal wave modes can explain these variations. Internal waves are generated by wind events, but can still be detected several days after the end of these events. Finally, our 24-h survey at one sampling point demonstrated that the V1H1 sinusoidal motion could evolve into nonlinear fronts. All these findings show that internal waves have a major impact on the distribution of P. rubescens proliferating in the metalimnic layer of a deep lake, and that this process could influence the growth of this species by a direct impact on light availability.
在一项为期两年的监测计划中，我们研究了高山深湖中蓝藻（Planktothrix rubescens）的垂直和水平分布，共设置了 11 个采样点，并在一个采样点进行了 24 小时调查。该物种已知在温带地区众多中深层营养丰富的湖泊的弱光层中大量繁殖，并且还会产生肝毒素。当我们观察整个湖泊中 P. rubescens 的分布时，我们发现水柱中生物量峰值的深度有很大的变化（高达 10 米）。这些变化与等温线位移密切相关。我们还发现湖中北部和南部的蓝藻生物量分布存在显著差异。我们使用物理建模方法证明，两种内波模式可以解释这些变化。内波是由风事件产生的，但在这些事件结束几天后仍能检测到。最后，我们在一个采样点进行的 24 小时调查表明，V1H1 正弦运动可以演变成非线性锋面。所有这些发现表明，内波对深湖中弱光层中大量繁殖的 P. rubescens 的分布有重大影响，而且这一过程可能通过直接影响光可用性来影响该物种的生长。
