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Lakes are essential ecosystems that provide a large number of ecosystem services whose quality is strongly impacted by human pressures. Optimal uses of lakes require adapted management practices which in turn rely on physico-chemical and biological monitoring. Long-term ecological monitoring provides large sets of environmental data. When such data are available, they have to be associated to metadata and to be stored properly to be accessible and useable by the scientific community. We present a data informatics system accessible to anyone who requests it. Maintained online since 2014 (https://si-ola.inrae.fr), it is originated from the Observatory on LAkes (OLA). It contains long-term data from 4 peri-alpine lakes (Lakes Aiguebelette, Annecy, Bourget, Geneva/Léman) and 24 high-altitude lakes of the northern French Alps. We describe the generated long-term data series, the data type, the methodologies and quality control procedures, and the information system where data are made accessible. Data use is allowed under the condition of providing reference to the original source. We show here how such a platform clearly enhances data sharing and scientific collaboration. Various studies referring to these data are regularly published in peer-reviewed journals; providing in fine a better understanding of lakes’ ecosystems functioning under local and global pressures.

A reliable and representative monitoring of phytoplankton abundance, especially cyanobacteria, is mandatory for choosing the best management or restoration strategy and for assessing its effectiveness in worldwide eutrophic lakes and reservoirs. In vivo and in situ fluorometry is expected to be faster than the traditional methods of phytoplankton counting and chlorophyll- a (chl a ) extraction and quantification. Contrary to water bodies in temperate climate, the technique still needs investigation in tropical freshwaters. We assessed the performance of a spectrofluorometer, the FluoroProbe (FP) in Lake Pampulha (Minas Gerais, Brazil), a water body where cyanobacteria are the dominant group most of the time. FP chl a concentrations were in average almost three times lower than spectrophotometric chl a concentrations and underestimation was larger when Chroococales were the dominant species. The linear response of the probe was limited to 100 μg chl a L −1 . The correlation between FP and spectrophotometric measurements was significant only for FP measurements below 100 μg chl a L −1 ( r = 0.84 , p 0.001 , n = 25 ). The correlations between FP measurements and biovolumes of phytoplankton ( r = 0.64 , p = 0.001 , n = 23 ) and cyanobacteria ( r = 0.60, p = 0.002 , n = 23 ) were significant but weaker than reported in temperate water bodies. Oscillatoriales fingerprint was the most distant from FP default fingerprint for cyanobacteria, presenting a lower relative fluorescence at 610 nm. Applying an average experimental fingerprint obtained from four dominant cyanobacteria species in Lake Pampulha allowed us to improve FP measurements compared to spectrophotometric data, especially when a single species, Planktothrix isothrix , was highly dominant. Even so, high phytoplankton biomass in Lake Pampulha led to high optical density, which disturbs FP measurements. Thus, in highly eutrophic water bodies, additional laboratory analysis is necessary to validate in situ spectrofluorometer measurements, more than in oligotrophic and mesotrophic environments.

RESUMO No processo de urbanização, o aumento na proporção de superfícies impermeabilizadas e as mudanças no uso do solo são responsáveis por maiores volumes e velocidades do escoamento superficial, refletindo em uma maior capacidade de arraste e em um maior aporte de nutrientes nos corpos d'água receptores. O objetivo deste trabalho foi implementar uma ferramenta matemática capaz de reproduzir o impacto de mudanças na bacia hidrográfica sobre a dinâmica do fitoplâncton em um lago urbano. Neste artigo são apresentados o desenvolvimento e os resultados de um modelo integrado constituído de um modelo hidrológico, para simular vazões escoadas em uma bacia hidrográfica, e de um modelo hidrodinâmico e ecológico, para simular a biomassa fitoplanctônica em um corpo d'água urbano. A Lagoa da Pampulha (Belo Horizonte, Minas Gerais), escolhida como estudo de caso, foi intensamente monitorada, assim como sua bacia de drenagem, entre outubro de 2011 e junho de 2013. Os dados obtidos foram utilizados para calibrar e validar ambos os modelos. Os resultados obtidos com o modelo hidrológico mostraram-se coerentes com as medidas realizadas em campo (o coeficiente de Nash variou entre 0,70 e 0,88). O modelo da lagoa representou corretamente a evolução da comunidade fitoplanctônica (erro médio absoluto normalizado: 0,25-0,42 e o coeficiente de Pearson: 0,82-0,89; p

International audience; Urban lakes mitigate the negative impacts on the hydrological cycle and improve the quality of life in cities. Worldwide, the concern increases for the protection and management of urban water bodies. Since the physical-chemical and biological conditions of a small aquatic ecosystem can vary rapidly over time, traditional low frequency measurement approaches (weekly or monthly sampling) limits the knowledge and the transfer of research outcomes to management decision-making. In this context, this paper presents an automatic monitoring system including a full-scale experimental site and a data transfer platform for high-frequency observations (every 5 min) in a small and shallow urban lake (Lake Champs-sur-Marne, Paris, France, 10.3 ha). Lake stratification and mixing periods can be clearly observed, these periods are compared with the dynamic patterns of chlorophyll-a, phycocyanin, dissolved oxygen and pH. The results indicate that the phytoplankton growth corresponds with dissolved oxygen cycles. However, thermal stratification cannot totally explain the entire dynamic patterns of different physical-chemical and ecological variables. Besides, the cyanobacteria is one of the dominating groups of phytoplankton blooms during the lake stratification periods (8 August–29 September 2016). During the cooling mixed period (29 September–19 October 2016), the high concentration of chlorophyll-a is mainly caused by the other phytoplankton species, such as diatoms. Perspectives are discussed in order to apply this observation system for real-time management of water bodies and lakes.