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Les lacs jouent un rôle particulier dans le cycle de l’eau dans les bassins versants urbains. La stratification thermique et le temps de séjour de l’eau élevé favorisent le développement phytoplanctonique. La plupart des métaux sont naturellement présents dans l’environnement à l’état de traces. Ils sont essentiels pour les organismes vivants. Néanmoins, certains métaux sont connus pour leurs effets toxiques sur les animaux et les humains. La concentration totale des métaux ne reflète pas leur toxicité. Elle dépend de leurs propriétés et de leur spéciation (fractions particulaires, dissoutes: labiles ou biodisponibles et inertes). Dans les systèmes aquatiques, les métaux peuvent être absorbés par des ligands organiques ou minéraux. Leur capacité à se complexer avec la matière organique dissoute (MOD), particulièrement les substances humiques, a été largement étudiée. Dans les lacs, le développement phytoplanctonique peut produire de la MOD non-humique, connue pour sa capacité complexante des métaux. Pourtant, peu de recherche sur la spéciation des métaux dans la colonne d’eau des lacs urbains a été réalisée jusqu’à présent.Les objectifs principaux de cette thèse sont (1) d’obtenir une base de données fiables des concentrations en métaux traces dans la colonne d’eau de lacs urbains représentatifs; (2) d’évaluer leur biodisponibilité via une technique de spéciation adéquate ; (3) d’analyser leur évolution saisonnière et spatiale et leur spéciation; (4) d’étudier l’impact des variables environnementales, en particulier de la MOD autochtone sur leur biodisponibilité; (5) de lier la concentration des métaux au mode d’occupation du sol du bassin versant.Notre méthodologie est basée sur un suivi in-situ des lacs en complément d’analyses spécifiques en laboratoire. L’étude a été conduite sur trois sites: le lac de Créteil (France), le lac de Pampulha (Brésil) et 49 lacs péri-urbains (Ile de France). Sur le lac de Créteil, plusieurs dispositifs de mesure en continu nous ont fourni une partie de la base de données limnologiques. Dans le bassin versant du lac de Pampulha, la pression anthropique est très importante. Le climat et le régime hydrologique des 2 lacs sont très différents. Les 49 lacs de la région d’Ile de France ont été échantillonnés une fois pendant trois étés successifs (2011-2013). Ces lacs nous ont fourni une base de données synoptique, représentative de la contamination métallique à l’échelle d’une région fortement anthropisée.Afin d’expliquer le rôle des variables environnementales sur la concentration métallique, le modèle Random Forest a été appliqué sur les bases de données du lac de Pampulha et des 49 lacs urbains avec 2 objectifs spécifiques: (1) dans le lac de Pampulha, comprendre le rôle des variables environnementales sur la fraction labile des métaux traces, potentiellement biodisponible et (2) dans les 49 lacs, comprendre la relation des variables environnementales, particulièrement au niveau du bassin versant, sur la concentration dissoute des métaux. L’analyse des relations entre métaux et variables environnementales constitue l’un des principaux résultats de cette thèse. Dans le lac de Pampulha, environ 80% de la variance du cobalt labile est expliqué par des variables limnologiques: Chla, O2, pH et P total. Pour les autres métaux, le modèle n’a pas réussi à expliquer plus de 50 % de la relation entre fraction labile et variables limnologiques. Dans les 49 lacs, le modèle Random Forest a donné un bon résultat pour le cobalt (60% de la variance expliquée) et un très bon résultat pour le nickel (86% de la variance expliquée). Pour Ni les variables explicatives sont liées au mode d’occupation du sol : « Activités » (Equipements pour l’eau et l’assainissement, entrepôts logistiques, bureaux…) et « Décharge ». Ce résultat est en accord avec le cas du lac de Créteil où la concentration en Ni dissous est très élevée et où les catégories d’occupation du sol « Activités » et « Décharges » sont dominantes / Lakes have a particular influence on the water cycle in urban catchments. Thermal stratification and a longer water residence time in the lake boost the phytoplankton production. Most metals are naturally found in the environment in trace amounts. Trace metals are essential to growth and reproduction of organisms. However, some are also well known for their toxic effects on animals and humans. Total metal concentrations do not reflect their ecotoxicity that depends on their properties and speciation (particulate, dissolved: labile or bioavailable and inert fractions). Trace metals can be adsorbed to various components in aquatic systems including inorganic and organic ligands. The ability of metal binding to dissolved organic matter (DOM), in particular humic substances, has been largely studied. In urban lakes, the phytoplankton development can produce autochthonous DOM, non humic substances that can have the ability of metal binding.. But there are few studies about trace metal speciation in lake water column.The main objectives of this thesis are (1) to obtain a consistent database of trace metal concentrations in the water column of representative urban lakes; (2) to access their bioavailability through an adapted speciation technique; (3) to analyze the seasonal and spatial evolution of the metals and their speciation; (4) to study the potential impact of environmental variables, particularly of dissolved organic matter related to phytoplankton production on metal bioavailability and (5) to link the metal concentrations to the land use in the lake watershed.Our methodology is based on a dense field survey of the water bodies in addition to specific laboratory analysis. The research has been conducted on three study sites: Lake Créteil (France), Lake Pampulha (Brazil) and a panel of 49 peri-urban lakes (Ile de France). Lake Créteil is an urban lake impacted by anthropogenic pollution. It benefits of a large number of monitoring equipment, which allowed us to collect a part of the data set. In Lake Pampulha catchment, the anthropogenic pressure is high. Lake Pampulha has to face with many pollution point and non-point sources. The climate and limnological characteristics of the lakes are also very different. The panel of 49 lakes of Ile de France was sampled once during three successive summers (2011-2013); they provided us with a synoptic, representative data set of the regional metal contamination in a densely anthropized region.In order to explain the role of the environmental variables on the metal concentrations, we applied the Random Forest model on the Lake Pampulha dataset and on the 49 urban lake dataset with 2 specific objectives: (1) in Lake Pampulha, understanding the role of environmental variables on the trace metal labile concentration, considered as potentially bioavailable and (2) in the 49 lakes, understanding the relationship of the environmental variables, more particularly the watershed variables, on the dissolved metal concentrations. The analysis of the relationships between the trace metal speciation and the environmental variables provided the following key results of this thesis.In Lake Pampulha, around 80% of the variance of the labile cobalt is explained by some limnological variables: Chl a, O2, pH, and total phosphorus. For the other metals, the RF model did not succeed in explaining more than 50% of the relationships between the metals and the limnological variables.In the 49 urban lakes in Ile de France, the RF model gave a good result for Co (66% of explained variance) and very satisfying for Ni (86% of explained variance). For Ni, the best explanatory variables are landuse variables such as “activities” (facilities for water, sanitation and energy, logistical warehouses, shops, office…) and “landfill”. This result fits with Lake Creteil where dissolved Ni concentration is particularly high and where the “activities” and “landfill” landuse categories are the highest

Eutrophication is one of the primary factors causing harmful cyanobacteria blooms in freshwater lakes; climate change such as warmer temperature can potentially further increase both frequency and intensity of blooms. This study investigated the long-term changes in water quality and summer phytoplankton assemblages in Oswego Lake, OR, in relation to lake management practices (e.g., hypolimnetic aeration and alum treatments), as well as climatic and regional meteorological conditions. Both water quality and phytoplankton assemblages were sampled biweekly during summer seasons between 2001 and 2013. The concentrations of total phosphorus (TP), soluble reactive phosphorus (SRP) and total nitrogen (TN) decreased 66%, 93% and 31%, respectively, in response to the hypolimnetic aeration and alum treatments since 2005. The results of summer phytoplankton assemblages showed a 62% reduction of cyanobacteria biovolume and a switch from cyanobacteria dominance (2001-2005) to diatom and chlorophyte dominance (2006-2013). Cluster analysis identified four statistically different groups of summer phytoplankton assemblages (denoted Groups 1-4). Nonmetric multidimensional scaling analysis indicated that the four groups were associated with different water quality conditions. Group 1 occurred prior to hypolimnetic aeration and was primarily comprised of cyanobacteria, associated with water conditions of high nutrients and high primary production. Group 2, dominated by cyanobacteria and chlorophytes, occurred between hypolimnetic aeration and alum surface application. Group 2 was associated with turbid water conditions. Group 3 was dominated by diatoms, occurring after alum surface application. Group 4 included R-strategist phytoplankton that quickly respond to environmental changes, occurring in the years following alum injection, drawdown and inflow alum treatment. Both Group 3 and 4 were associated with reduced nutrients in the lake. The results demonstrated a strong temporal relationship between the long-term changes in water quality and summer phytoplankton assemblages and the lake management practices. The Pacific Decadal Oscillation (PDO) index, an El-Niño-like pattern of Pacific climate variability, showed a statistically significant correlation with the summer phytoplankton dynamics, while the multivariate ENSO index (MEI) and regional meteorological variables (air temperature, rainfall, wind speed, wind direction and solar radiation) were not significantly related to the changes of phytoplankton communities during the study period. In conclusion, the study results suggest that the lake management practices had strong effects on both production and community compositions of phytoplankton, and suggest the need for a future study on large-scale climate impacts on lake ecosystems and best management practice.

Relatively little published information on cyanoprokaryote (blue-green algal) blooms in the freshwater wetlands in Western Australia is available. There has been little research on the urban lakes and rivers, examining the relationship between environmental conditions and toxin-producing blooms. In this project the ecology, morphology and toxicity of cyanoprokaryota blooms in 27 metropolitan lakes and sumplands, as well as three major rivers, from 2000 to 2003, on the Swan Coastal Plain (SCP) in the southwest of Western Australia were investigated. / A total of 24 species were identified and described, of which nine species had not been previously documented in the area. This included the potentially toxic species Cylindrospermopsis raciborskii, Aphanizomenon ovalisporum and Anabaena bergii var. limnetica. An illustrated guide to the common bloom-forming species was generated using conventional taxonomic criteria. / Microcystis flos-aquae and Microcystis aeruginosa were the dominant bloom-forming cyanoprokaryotes, widespread in their distribution. Anabaena circinalis, A. bergii var. limnetica and Anabaenopsis elenkinii were the common filamentous species. Anabaena circinalis was common to certain freshwater sites, while A. bergii var. limnetica and A. elenkinii occurred in salinity ranging from fresh (< 1ppt) to hyposaline (3-10 ppt). Sites with similar species assemblages were identified using two-way indicator species analysis and clustering analysis. From this, a distinct distribution pattern emerged, which was defined by the main genera observed in the lakes – Microcystis, Anabaena, Aphanizomenon and Anabaenopsis. / The spatial and temporal distribution of the common bloom-forming cyanoprokaryote species was examined in conjunction with spring-summer physico-chemical data using principal component analysis. It was found that pH, water temperature and electrical conductivity/salinity accounted for variations among the lakes, with electrical conductivity the variable explaining the greatest variation. Lakes located on the coast, or further inland at the base of the Darling Scarp, were more hyposaline to saline, and the remaining lakes were fresh. Although the SCP lakes form consanguineous groups based on geochemistry and hydrology, no similarities among them were found in terms of water quality. / The relationship between nitrogen (N) and phosphorus (P) concentrations (total and dissolved inorganic) and cyanoprokaryote community structure (N-fixing versus non-N-fixing species) was investigated in five selected lakes; Yangebup Lake, Bibra Lake, Blue Gum Lake, Tomato Lake and Emu Lake. The lakes ranged from mesotrophic to eutrophic and supported spring-summer blooms containing multiple species. Overall an inverse relationship between cyanoprokaryote abundance and total ambient nutrient concentrations at the time of the blooms was evident. No transition in dominance in the community was observed in Yangebup Lake, Emu Lake and Bibra Lake, as they were dominated by non-heterocytic species (M. aeruginosa and M. flos-aquae) throughout spring and summer. For Yangebup Lake and Bibra Lake, the abundance of non-heterocytic species decreased concomitantly with decreasing dissolved inorganic N. In contrast, heterocytic species (A. circinalis) dominated the spring community in Tomato Lake, and summer community in Blue Gum Lake, when N and P concentrations were at their highest. / The presence of microcystins in Microcystis dominated blooms was examined using high performance chromatography. A total of 32 natural bloom samples, representing 13 lakes, were analysed for microcystin variants; -LR, -RR and -YR. Twenty-eight samples proved to be toxic with the highest total microcystin concentration from 1645 to 8428.6 µg L[superscript]-1, the lowest concentrations were less than 10 µg L[superscript]-1 with some below the detection limit. Microcystis aeruginosa and M. flos-aquae were associated with these microcystin-containing blooms, although M. flos-aquae appear to be less toxic. The presence of Nodularia spumigena in the Lake Yangebup was associated with high concentrations of nodularin (1664 µg L[superscript]-1). / Employing enzyme-linked immunosorbent assay for microcystins and the brine shrimp (Artemia) bioassays allowed a greater number of lake samples to be analysed and provided a rapid assessment of toxicity. The three methods for cyanotoxin detection verified Yangebup Lake, Herdsman Lake, Hyde Park, Jackadder Lake and Emu Lake as highly toxic sites. Low toxicity was demonstrated in samples from Lake Goollelal, Lake Joondalup, Lake Claremont, Blue Gum Lake and North Lake. These results provided the first evidence of cyanotoxin producing blooms in urban lakes of the SCP. / A comparative study on cyanoprokaryota blooms in Swan River estuary, upper Canning River and upper Serpentine River found that these sites, although hyposaline to saline, contained species that were common in the freshwater lakes. Sampling the river systems showed M. aeruginosa, M. flos-aquae, A. circinalis, A. elenkinii and Planktothrix planctonica to be cosmopolitan in distribution, present in SCP wetlands of varied salinity. Similarities between the upper Canning River and lakes in environmental conditions and species assemblage were demonstrated using multivariate analyses. / Toxin analysis of bloom samples from the Swan River and upper Canning River revealed microcystin concentrations were less than that of the surrounding lakes (1.05-124.16 µg L[superscript]-1). Similarly, nodularin concentrations were higher in Yangebup Lake than the upper Serpentine River. However, the dominance of Anabaena in Canning River samples, and the highly toxic result from the Artemia bioassay suggests microcystin is not the predominant cyanotoxin in this wetland. / This study has produced an overview of the distribution and morphology of cyanotoxin-producing cyanoprokaryotes in the SCP wetlands. The data presented provide the basis for further cyanoprokaryote research in Western Australia, in particular the molecular characterisation of bloom-forming toxic species.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-03-27T11:30:41Z No. of bitstreams: 0 / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-03-27T13:52:08Z (GMT) No. of bitstreams: 0 / Made available in DSpace on 2018-03-27T13:52:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-06-30 / Florações de cianobactérias são consequência principalmente da eutrofização de ambientes aquáticos que afeta a qualidade e compromete o uso da água para diversas finalidades. A restauração de sistemas aquáticos eutrofizados é um dos principais desafios da limnologia atual. Nosso objetivo foi identificar as principais causas do processo de eutrofização e ocorrência de florações de cianobactérias e testar a eficácia e aplicabilidade do uso combinado de coagulantes e adsorventes de P em fase sólida no controle da eutrofização e florações em um lago tropical raso. O estudo foi conduzido no lago do Museu Mariano Procópio, localizado em Juiz de Fora – MG e dividido em quatro fases. As duas primeiras fases compreendem uma análise sistêmica do lago. Na primeira, buscou-se conhecer a dinâmica da comunidade fitoplanctônica a fim de entender a dominância de cianobactéria deste sistema. Na segunda, foram avaliados os aportes de fósforo (P) para o sistema. Na terceira fase foram realizados experimentos em laboratório, para verificar a eficácia de diferentes coagulantes e lastros para remoção de cianobactérias. E na quarta fase foram realizados experimentos em mesocosmos no lago, para testar o controle da eutrofização e florações de cianobactérias. A análise sistêmica mostrou dominância de diferentes espécies de cianobactérias e que as altas concentrações de nutrientes presentes do sistema vêm principalmente de contribuição externa. O uso combinado de coagulantes e lastros foi eficiente para a remoção de biomassa de cianobactérias, porém foi dependente da espécie. Nos experimentos com mesocosmos, foi observada uma forte redução de Clorofila a (Chl a 85%) e fósforo total (TP 78%) (p <0,0010) em todos os tratamentos, porém estas reduções não se mantiveram ao longo do tempo. Para mitigar as florações de cianobactérias deste sistema, será necessário o controle das fontes externas de nutrientes e um ajuste na técnica de coagulante-lastro para manter a clorofila e o fósforo total em concentrações reduzidas por mais tempo. / Cyanobacterial Blooms are mainly a consequence of eutrophication of aquatic environments that affect the water quality and compromise the use of water for various purposes. The restoration of eutrophic aquatic systems is one of the main challenges of today's limnology. Our objective was to identify the main causes of the eutrophication process and the occurrence of cyanobacterial blooms in a shallow tropical lake, and to test the efficacy and applicability of the combined use of coagulants and adsorbents of P in solid phase for the control of eutrophication and cyanobacteria blooms in a tropical shallow system. The study was conducted in the lake of the Mariano Procópio Museum, located in Juiz de Fora - MG and divided into four phases. The first two phases comprised a systemic analysis of the lake. The first one sought to know the dynamics of the phytoplankton community and to understand the causes of the cyanobacteria dominance in this system. In the second one, the main contributions of phosphorus to the system and the general balance of P were evaluated. In the third phase, laboratory experiments were carried out to evaluate the efficacy of different coagulants and ballasts for the removal of cyanobacteria. Last, in the fourth phase experiments were carried out in mesocosmos in the lake to test the control of eutrophication and cyanobacterial blooms. The systemic analysis showed the dominance of different species of cyanobacteria and that the high concentrations of nutrients present in the system come mainly from external contribution. The combined use of coagulants and ballasts was efficient for the removal of cyanobacteria biomass, but it is dependent on the species pool. In the experiments with mesocosms, a strong reductions of chloropyll a (Chl a) 85% and total phosphorus (TP) 78% (p < 0.001) were observed in all treatments, however these reductions were not lasting. To mitigate the cyanobacterial blooms of this system, it will be necessary to control the external sources of nutrients and also an adjustment in the coagulant-ballast technique to keep Chl a l and TP in reduced concentrations for longer time.