The proliferation of the toxic cyanobacterium Planktothrix rubescens following restoration of the largest natural French lake (Lac du Bourget)
The proliferation of the toxic cyanobacterium Planktothrix rubescens following restoration of the largest natural French lake (Lac du Bourget)
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DOI：
10.1016/j.hal.2003.12.006
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发表时间：
2005-06-01
期刊：
影响因子：
6.6
通讯作者：
Humbert, JF
中科院分区：
文献类型：
--
作者：
Jacquet, S;Briand, JF;Humbert, JF
布尔歇湖位于阿尔卑斯山，是法国最大的天然湖泊。经过 20 世纪 70 年代和 80 年代初的重大修复计划，包括大力减少湖泊中的营养负荷和污染，水质在过去二十年中得到了改善。这可以从硝酸盐：磷酸盐比例的增加、“清水阶段”的强化（即春季水柱透明度的增加）以及总磷和叶绿素a浓度的降低来推断。然而，自 1996 年以来，丝状、富含藻红蛋白、非固氮且具有肝毒性的蓝细菌冬凌藻浮丝菌 (Planktothrix rubescens) 的大量繁殖一直持续到随后，至少在夏季和秋季期间。营养物质（尤其是磷）通常被认为是导致蓝藻大量繁殖的最重要因素之一，因此有人提出这样的问题：这种大量繁殖是否是恢复计划的一个矛盾结果？利用从布尔歇湖调查、文献和最近的实验室实验中获取的大量数据，以及邻近日内瓦湖的现场数据，我们提出了一个现实的场景来解释蓝藻的种群动态以及布尔歇湖水华的发生和维持。为了解释这种水华，必须考虑到湖泊的特征（高水柱稳定性、过去十年营养贫乏层加深、水停留时间长）、当地条件（营养负荷和电荷）和全球变化（全球变暖）。我们认为，冬凌草在布尔热湖的成功可能是由于透明度的增加和分层周期的延长，因为（1）减少磷后对其他浮游植物物种的限制，使得冬凌草能够利用有机磷来提高其竞争力； (2) 比平均冬季/春季温暖，允许更早的水层化，最终为冬凌草带来竞争优势； (3) 低于平均表面辐照度，这也给喜弱光的冬凌草带来了优势。最后，这项研究强调了长期数据集在试图阐明重大生态问题（例如蓝藻水华）的全球原因以及对淡水生态系统功能和利用的影响方面的重要性。 (c) 2004 Elsevier B.V. 保留所有权利。
Lac du Bourget, in the Alps, is the largest natural French lake. Following major restoration programmes during the 1970s and early 1980s, involving massive efforts to reduce nutrient loads and pollution in the lake, the water quality has improved over the past two decades. This can be inferred from the increase in the nitrate: phosphate ratio, the intensification of the "clear-water phase" (i.e. the increase in the water column transparency in spring), and the reduction in the total phosphorus and chlorophyll a concentrations. However, blooms of the filamentous, phycoerythrin-rich, non-nitrogen fixing and hepatotoxic cyanobacterium Planktothrix rubescens have occurred since 1996 and have been maintained subsequently, at least during summer and autumn periods. Nutrients (especially phosphorus) are usually thought to be one of the most important factors responsible for cyanobacterial blooms, and so the question is asked if this bloom is a paradoxical outcome of the restoration programs? Using a large set of data taken from surveys of Lac du Bourget, from the literature, and from recent laboratory experiments, and also using field data for the neighboring Lake Geneva, we propose a realistic scenario to account for the population dynamics of the cyanobacterium and the occurrence and maintenance of the bloom in Lac du Bourget. The characteristics of the lake (high water column stability, deepening of the nutrient-depleted layer during the last decade, a long water residence time), local conditions (the nutrient load and charge) and global changes (global warming) all had to be taken into account to explain this bloom. We suggest that the success of P. rubescens in Lac du Bourget is probably due to increased transparency and a longer stratified period following (1) the restriction of other phytoplankton species following reduced phosphorus, which has allowed P. rubescens to make use of organic phosphorus to improve its competitiveness; (2) warmer than average winter/spring periods allowing an earlier water stratification and in fine a competitive advantage to P. rubescens; (3) lower than average surface irradiance, which has also given the low-light preferring P. rubescens an advantage. Finally, this study highlights the importance of long-term data sets in attempting to elucidate the global causes of a major ecological problem (such as this cyanobacterial bloom) and impacts with regard to the function and use of freshwater ecosystems. (c) 2004 Elsevier B.V. All rights reserved.