Quelques pêches planctoniques dans le lac du Bourget et les lacs voisins

Bourrelly, P.

doi:10.1080/03680770.1950.11895292

Cited by 1 publication

(3 citation statements)

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“…1). Despite the importance of this lake, both in terms of its size and utilization (fisheries, drinking water supply and recreational activities), there have been only a few studies of the plankton ecology of this lake, and most of the literature has appeared as articles or reports in French (Leroux, 1928;Hubault, 1947;Bourrelly, 1949Bourrelly, , 1955Laurent, 1966;Balland, 1976;CEMAGREF reports, 1985CEMAGREF reports, , 1990CEREVE report, 1998). Only recently, have attempts been made to study phytoplankton variability and dynamics and to build predictive models of the water quality of Lac du Bourget (Vinçon-Leite et al, 1995Tassin and Vinçon-Leite, 1998).…”

Section: Description Of the Sitementioning

confidence: 96%

“…With regard to the change in nutrient concentration, Lac du Bourget was considered as oligotrophic in the 1940s and 1950s (Hubault, 1943(Hubault, , 1947Bourrelly, 1955). It underwent rapid eutrophication from the 1960s, and the total phosphorus concentration reached more than 120 g l −1 in the early 1980s (Vinçon-Leite et al, 2002).…”

Section: Global Change In Lac Du Bourget Since the 1950smentioning

confidence: 98%

“…What can be inferred from the changes in these two parameters during the period analysed is that the phytoplankton community and the population succession pattern have changed. In the 1950s, P. rubescens was reported to be relatively rare (Bourrelly, 1955), and Laurent (1966) reported a major proliferation of the green and filamentous alga Mougeotia gracillima in 1957. At the end of the 1960s, when the lake was definitely reported to be eutrophic, the phytoplankton consisted mainly of cyanobacteria including Aphanizomenon flos-aquae (40%), and diatoms including Fragilaria crotonensis, Aulacoseira granulata and Melosira granulata (50%).…”

Section: Global Change In Lac Du Bourget Since the 1950smentioning

confidence: 99%

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The proliferation of the toxic cyanobacterium Planktothrix rubescens following restoration of the largest natural French lake (Lac du Bourget)

Jacquet¹,

Briand²,

Leboulanger³

et al. 2005

Harmful Algae

176

183

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International audienceLac 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

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