Diese Arbeit behandelt die Charakterisierung der Habitate und die Langzeit-Entwicklung über sechs Jahrzehnte der Makrophytenvegetation nordwestdeutscher Bäche und Flüsse, um zum Wissen über die Ökologie aquatischer Makrophyten beizutragen und sie als Bioindikatoren zu nutzen. Siebzig Bäche und Flüsse der Regionen Ems-Hunte Geest, Lüneburger Heide, Allerflachland, nördliches Harzvorland, Fuß des Weser-Leine Berglandes und ostholsteinisches Hügelland sind Bestandteil der Studie, wobei der Schwerpunkt auf der überregionalen Betrachtungsebene liegt. Aus der Analyse der Zusammensetzung und Verbreitung der Makrophytengesellschaften im Zusammenhang mit Gewässergröße und physikalischen und chemischen Wasser- und Sedimenteigenschaften schlossen wir, dass Gewässertiefe und Fließgeschwindigkeit von den gemessenen Variablen den größten Einfluss auf die heutige Gesellschaftszusammensetzung haben, gefolgt vom Gehalt pflanzenverfügbaren Phosphors im Sediment. Es ist jedoch nicht auszuschließen, dass vor der im Untersuchungsgebiet seit den 1950ern stattfindenden, starken Intensivierung der landwirtschaftlichen Nutzung, als noch ausgeprägtere Gradienten bei den Nährstoffgehalten der Fließgewässer existiert haben, chemische Größen einen stärkeren Einfluss auf die Makrophytenvorkommen hatten als heute. Mittels semi-permanenter Dauerflächen haben wir den Vegetationswandel zwischen den 1950ern und 2010 untersucht und einen dramatischen Rückgang der Artenvielfalt festgestellt (der Gesamtartenpool sank um 27.5 % von 51 auf 37 Hydrophytenarten, die Artenzahl pro Aufnahmefläche um 19.4 % von 4.7 auf 3.8 Arten), begleitet von einem umfassenden Bestandsumbau vom Vorherrschen wurzelnder (v.a. potamider) Arten zur Dominanz freischwimmender (v.a. lemnider) Arten. Oligotraphente Arten wie Potamogeton gramineus und P. polygonifolius sind in den Probeflächen ausgestorben und die mesotraphenten Arten Myriophyllum alterniflorum und Ranunculus peltatus in ihrer Auftretenshäufigkeit um mehr als 50 % zurückgegangen, während die eutraphenten Arten Myriophyllum spicatum und Spirodela polyrhiza um mehr als 100 % zugenommen haben. In den Artmerkmalen Blattausdauer und spezifische Blattfläche (SLA) wurden Änderungen festgestellt: In den historischen Makrophytenbeständen der 1950er waren immergrüne Arten und Arten mit dünnen Blättern oder solchen mit viel arenchymatischem Gewebe häufig (große SLA), während die rezenten Bestände von 2010 durch sommergrüne Arten und solche mit robuster Struktur (geringe SLA) gekennzeichnet sind. Die Veränderungen in der Arten-zusammensetzung waren am tiefgreifendsten in der Region Ems-Hunte Geest, wo weitläufige Niedermoore durch Entwässerung insbesondere seit der Eindeichung des Dümmer Sees (1953) intensiv bewirtschaftetem Agrarland gewichen sind, und weniger ausgeprägt in der Lüneburger Heide, einer der wenigen Tieflandsregionen Deutschlands, in der noch Fließgewässer mit kaum durch den Menschen veränderter Struktur zu finden sind. Auf der syntaxonomischen Ebene zeigte die Anwendung zweier unterschiedlicher pflanzensoziologischer Klassifikationssysteme tiefe Veränderungen in der Struktur der Makrophytengesellschaften über sechs Jahrzehnte auf. Alle dokumentierten Vegetations-bestände konnten einer der Klassen Potamogetonetea, Lemnetea, Phragmitetea oder Fontinalietea zugeordnet werden. Während Batrachietalia/Batrachion und Potamogetonetalia /Potamogetonion-Bestände stark zurückgegangen sind, haben Nymphaeetalia/Nymphaeion-Gesellschaften zugenommen. Die beobachtete Zunahme pflanzensoziologisch schwach charakterisierter Bestände (Fragmentgesellschaften) deutet auf Verluste bei den hoch-spezialisierten Arten hin. Im Schnitt waren sich die rezenten Vegetationsbestände signifikant ähnlicher (SBC=0.25) als die historischen (0.22), was eine Homogenisierung der Fließgewässervegetation Nordwestdeutschlands offenbart. Beschleunigte Eutrophierungsprozesse in den Gewässern und wasserbauliche Maßnahmen in der intensiv genutzten Kulturlandschaft haben zu einer Uniformierung der Fließgewässerhabitate geführt, worin neben häufigen Störereignissen die Hauptursache für die Verluste in Artenreichtum und Vielfalt der Makrophytenvegetation gesehen werden kann. Weitere Anstrengungen zur Reduzierung der Nährstofffrachten, sowie eine Erhöhung der Habitatheterogenität durch strukturverbessernde Renaturierungsmaßnahmen und ökologisch verträgliche Unterhaltungstechniken und -zeitpunkte sind notwendig, um den Diversitäts-rückgang in der Makrophytenvegetation nordwestdeutscher Bäche und Flüsse aufzuhalten und umzukehren. Eine artenreiche Vegetation ist ein wichtiger Baustein in Fließgewässer-Ökosystemen, deren Funktionsfähigkeit nicht zuletzt auch für das menschliche Wohlergehen von Bedeutung ist.

Baigiamojo darbo tema „Švenčionių rajono ežerų būklės vertinimas taikant bioindikacinius metodus“. Darbo struktūrą lėmė siekis nagrinėti bioindikacinius gėlojo vandens telkinių vertinimo metodus, kuriuos galima taikyti vertinant ežerus, jų trofinį statusą, prognozuoti ežerų tolimesnį likimą. Dėl to literatūros ir kitų informacijos šaltinių analizėje išskiriamos aštuonios pagrindinės dalys. Jose plačiai aptariamas bioindikacinis vandens telkinių vertinimas, galimybės. Kalbama apie ežerų struktūrą, suskirstymą, ežerų augaliją ir jos panaudojimą bioindikacijoje. Atrenkant bioindikacinius vertinimo metodus, atsižvelgta į jų populiarumą, naujumą ir praktiškumą, todėl aprašyti ir šiuo metu dar mažai žinomi bioindikaciniai vertinimo metodai. / The topic “Evaluation of Švenčionys district lakes state applying bioindicational methods” was not chosen occasionally. The structure of the work was determined by the aim to analyze bioindicator-based methods of water body assessment that may be applied when assessing lakes, their trophic state, and forecasting their further destiny. Therefore analysis of references and other sources of information are divided into eight sections intended to comprehensively discuss bioindicator-based assessment of water bodies, and its possibilities. Structure, distribution, and flora of lakes, as well as its use in bioindication are overviewed.

Bakalauro darbo tikslas - pagal kerpių rūšių gausumą ir kerpėmis dengiamą plotą ant medžių kamienų tam tikrame objekte nustatyti oro užterštumą. Darbo objektas – kerpės, augančios Kuršėnų mieste ant medžių katilinės poveikio zonoje. Darbas atlikas 2012 metų liepos - rugpjūčio mėnesiais. Kuršėnų mieste vyraujantys vėjai yra pietvakarių. Nuo katilinės vyraujančių vėjų kryptimi (PV) pažymėtame transekte 1 km intervalais išdėstyti 5 tyrimo bareliai (30x30 m pločio). Tokia pat tvarka nuo darbo objekto išdėstyti 5 tyrimo bareliai priešinga kryptimi (prieš vyraujančių vėjų kryptį (ŠR)). Kiekviename barelyje nuo kiekvienos medžių rūšies buvo paimti kerpių mėginiai, nustatytas jų kamieno procentinis padengimas. Darbe nustatytos visos kerpių rūšys, augančios ant medžių kamienų. Tirtoje teritorijoje identifikuota 15 kerpių rūšių: 7 lapiškosios ir 8 žiauberiškosios. Daugiausiai kerpių rūšių aptikta trijuose bareliuose kurie yra nutolę 4 ir 5 kilometrais nuo taršos objekto prieš vyraujančių vėjų kryptį (ŠR) ir 5 kilometrais pagal vyraujančių vėjų kryptį (PV) šiuose bareliuose buvo rasta po 6 kerpių rūšis. / The aim of this final paper of the Bachelor degree is measuring air pollution according to the abundance of species of lichens as well as the area covered by lichens on the trunks of the trees. The object of this work is lichens who grow on trees in Kuršėnai city. Pollution source is boiler-house of “Siauliai Energy”. Experiment was carried out in July - August months 2012. Kuršėnai is dominated by southwestern (SW) winds. In the selected transect stretching from the boiler-house in the direction of prevailing winds, southwest (SW), the study plots (30x30 m) were located at 1 km intervals from each other. According to the same ordering, study plots in the opposite direction were set out (against the prevailing wind direction (NE)). This paper identifies all kinds of lichen that grow on tree trunks in the area. Fifteen species of lichens were identified in the investigated area. More specifically, 7 foliose and 8 crustose were found. Most species of lichen grow in the outskirts of the city, while the least amount of them was found close to the source of pollution.

Darbo tema: Šiaulių miesto Vijolės ir Kelmės miesto Kražantės upių vandens kokybės nustatymas ir palyginimas pagal titnagdumblių rūšinę įvairovę nustatant saprobiškumo indeksus (SI). Tyrimo tikslas buvo atlikti epifitinių ir epilitinių titnagdumblių analizę ir pagal jos rezultatus, apibūdinti upių Vijolės ir Kražantės vandens kokybę. Tikslui pasiekti pasirinkti uždaviniai: nustatyti titnagdumblių rūšių įvairovę Vijolės ir Kražantės upėse; apskaičiuoti tiriamųjų upių saprobiškumo indeksus; palyginti tyrimo rezultatus su ankščiau atliktų vertinimų rezultatais. Darbo objektu pasirinkta Vijolės upė tekanti per Šiaulių miestą ir Kražantės upė tekanti per Kelmės miestą. Mėginiai buvo imami 2013 metų pavasario, vasaros ir rudens sezonu, fiksuojami lugol‘o tirpalu, nusodinami naudojant centrifūgą. Mėginiai buvo mikroskopuojami naudojant 600x didinantį mikroskopą. Titnagdumbliai atpažinti spausdintais ir internetiniais šaltiniais. Saprobiškumo indeksui apskaičiuoti buvo naudojama metodika pagal LR ministro įsakymą, paviršinio vandens telkinių tyrimo metodiką pagal fitoplanktoną. Tyrimo metu buvo aptiktos ir atpažintos 52 titnagdumblių rūšys priskiriamos 2 klasėms ir 4 eilėms. Kražantės upė pasižymėjo didesne rūšių įvairove negu Vijolės. Abejose upėse dažniausiai pasitaikančios mėginyje rūšys buvo Navicula pusilla W. Sm., Navicula lanceolata (Ag.) Kütz., taip pat didžiausią masę mėginyje sudarė Navicula Bory genties rūšys. Daugiausia titnagdumblių Vijolės upėje buvo aptikta pavasarį... [toliau žr. visą tekstą] / The main thesis: the quality of water determination and comparison, according to species variety of diatoms, setting the saprobic indexes (SI) at Vijolė river in Šiauliai and Kražantė river in Kelmė. The purpose of the work is to analyse the diatoms, also to describe the quality of water in Vijolė and Kražantė rivers, using the rezults of these analysis. To achieve the goal, these tasks have been chosen: to determine the variety of diatoms in Vijolė and Kražantė rivers; to calculate the saprobic indexes of the rivers explored; to compare the rezults of investigation with rezults of evaluation, made earlier at the areas of investigation. The object of this work is Vijolė river in Šiauliai town, also Kražantė river in Kelmė town. The samples have been taken at the 2013 year‘s spring, summer and autumn seasons. They have been located using the lugol soak, precipitated using the centrifuge. The samples have been explored using the 600x microscope. The diatoms have been recognized using the information of printed and online sourses. The saprobic index was calculated using the methodology in accordance with an order of the LR Minister. The method of surface water bodies – according to phytoplankton. 52 species of diatoms, assigned to 2 categories and 4 ranges, have been detected at the time of research. Kražantė river characterized with higher variety of species, than Vijolė river. In both rivers, the most common species in sample have been Navicula pusilla W. Sm., Navicula... [to full text]

Growth and survival of juvenile pearl mussels (Margaritifera margaritifera Linnaeus, 1758) "in-situ" indicates suitable habitats for their rearing and subsequent reintroduction. Six streams in Aš region (Rokytnice, Lužní potok, Pekelský potok, Újezdský potok, Perlový potok, Bockbach) including 15 profiles were evaluated throughout the season (1. 6. 31. 8. 2015). One year old pearl mussels (n = 580) sized from 700 1400 ?m. Mean survival of pearl mussels was 63 % in all streams. Mean absolute growth increment attained 755 ?m throughout the season. Growth of pearl mussels (1+) was positively correlated with the water temperature (R2 = 0,1084). Both the highest survival (70 %) and the highest absolute growth (1027 ?m and 997 ?m) of pearl mussels was determined on localities in Bockbach (Bockbach 11 and 1). In contrast to Bockbach 11 and 1 mean survival (28%) and absolute growth (304 ?m) was the lowest in Lužní potok 2. Survival rate of two years old pearl mussels was higher than that of one year old pearl mussels. Both of these age categories grew similarly.

A contribuição deste trabalho é apresentar uma metodologia de avaliação de risco ecológico do ambiente aquático utilizando-se dados provenientes de programas de monitoramento ambiental. O estudo tem como cenário um trecho do Rio Jacuí, município de São Jerônimo – RS, Brasil, que foi avaliado através da aplicação de um programa de monitoramento ambiental. Consideraram-se como variável explicativa deste estudo, as evidências registradas nos compartimentos abióticos, água superficial e sedimento. As evidências químicas foram decorrentes da presença dos metais Hg, Pb e Zn e as evidências ecotoxicológicas de ensaios de toxicidade aquática com Ceriodaphinia dubia para água superficial e Hyalella azteca para sedimento. Consideraram-se como variáveis respostas as evidências biológicas compostas pelos dados de riqueza, índice de Shannon-Weaver, equitatividade e densidade numérica das espécies das comunidades zooplantônica e bentônica. O risco ecológico (Baixo, Médio e Alto) foi caracterizado pela associação à qualidade ambiental (Ótima, Alerta e Crítica), respectivamente, estabelecida pelas evidências registradas. Os resultados permitem considerar que é possível o uso de programas de monitoramento ambiental para avaliação de risco ecológico, se contiverem, além dos dados químicos e ecotoxicológicos exigidos pela legislação ambiental, dados do monitoramento da biota residente. / The contribution of this work is to present a methodology for ecological risk assessment in an aquatic environment using data derived from environmental monitoring programs. The location focused by this study was a segment of the Jacuí River, in the town of São Jerônimo – RS, Brazil, which was assessed by applying an environmental monitoring program. The evidence recorded from the abiotic compartments surface water and sediments was considered an explanatory variable. The chemical evidence stemmed from the presence of Hg, Pb and Zn, while the ecotoxicological evidence resulted from aquatic toxicity tests using Ceriodaphinia dubia for surface water and Hyalella azteca for sediments. The biological evidence from the Shannon-Weaver index, species richness, equitability and numerical density data in zooplanktonic and benthonic communities was considered the response variable. The ecological risk (Low, Medium, and High) was characterized by the association with environmental quality (Great, Warning, and Critical), established by the evidence recorded. The results have shown that it is possible to use environmental monitoring programs to evaluate of ecological risk assessment, if they have chemical and ecotoxicological data required by environmental laws, and monitoring data of resident biota.

A contribuição deste trabalho é apresentar uma metodologia de avaliação de risco ecológico do ambiente aquático utilizando-se dados provenientes de programas de monitoramento ambiental. O estudo tem como cenário um trecho do Rio Jacuí, município de São Jerônimo – RS, Brasil, que foi avaliado através da aplicação de um programa de monitoramento ambiental. Consideraram-se como variável explicativa deste estudo, as evidências registradas nos compartimentos abióticos, água superficial e sedimento. As evidências químicas foram decorrentes da presença dos metais Hg, Pb e Zn e as evidências ecotoxicológicas de ensaios de toxicidade aquática com Ceriodaphinia dubia para água superficial e Hyalella azteca para sedimento. Consideraram-se como variáveis respostas as evidências biológicas compostas pelos dados de riqueza, índice de Shannon-Weaver, equitatividade e densidade numérica das espécies das comunidades zooplantônica e bentônica. O risco ecológico (Baixo, Médio e Alto) foi caracterizado pela associação à qualidade ambiental (Ótima, Alerta e Crítica), respectivamente, estabelecida pelas evidências registradas. Os resultados permitem considerar que é possível o uso de programas de monitoramento ambiental para avaliação de risco ecológico, se contiverem, além dos dados químicos e ecotoxicológicos exigidos pela legislação ambiental, dados do monitoramento da biota residente. / The contribution of this work is to present a methodology for ecological risk assessment in an aquatic environment using data derived from environmental monitoring programs. The location focused by this study was a segment of the Jacuí River, in the town of São Jerônimo – RS, Brazil, which was assessed by applying an environmental monitoring program. The evidence recorded from the abiotic compartments surface water and sediments was considered an explanatory variable. The chemical evidence stemmed from the presence of Hg, Pb and Zn, while the ecotoxicological evidence resulted from aquatic toxicity tests using Ceriodaphinia dubia for surface water and Hyalella azteca for sediments. The biological evidence from the Shannon-Weaver index, species richness, equitability and numerical density data in zooplanktonic and benthonic communities was considered the response variable. The ecological risk (Low, Medium, and High) was characterized by the association with environmental quality (Great, Warning, and Critical), established by the evidence recorded. The results have shown that it is possible to use environmental monitoring programs to evaluate of ecological risk assessment, if they have chemical and ecotoxicological data required by environmental laws, and monitoring data of resident biota.

Les diatomées sont des microalgues ubiquistes d'une diversité exceptionnelle. Cela en fait de bons indicateurs de la qualité des écosystèmes aquatiques et sont utilisées depuis plus de 50 ans. Depuis l'année 2000, la Directive Cadre Européenne sur l'Eau impose leur utilisation pour évaluer la qualité écologique des cours d'eau. Un cadre typologique doit être utilisé afin de comparer des rivières comparables entre elles, c'est-à-dire des rivières de mêmes régions bioclimatiques, coulant sur les mêmes substrats géologiques et à des altitudes comparables. Différentes classifications écorégionales ont été définies sur la base de ces paramètres. Nous avons montré qu'à une échelle couvrant 4 pays (Espagne, France, Italie, Suisse) et à une régionale (Nord-est de la France), les écorégions et la géologie sont déterminantes pour expliquer les communautés. Les paramètres caractérisant la pollution sont moins importants. Contrairement à certains auteurs, nous n'avons pas observé d'homogénéisation des communautés lorsque le niveau de pollution augmente. D'autre part nous n'avons pas observé de communautés restreintes géographiquement : cela permettrait de rassembler des écorégions distinctes géographiquement mais présentant les mêmes caractéristiques physiques. Les diatomées présentent une diversité spécifique très importante qui peut être un frein à leur utilisation en routine. Nous avons montré qu'en augmentant la précision de détermination (de la subdivision à l'espèce), les performances d'évaluation de la pollution augmentait mais beaucoup moins que le nombre de taxons. Les performances d'évaluation entre le genre et l'espèce sont d'ailleurs proches, alors qu'il y a dix fois plus d'espèce que de genres. Nous avons montré aussi que des métriques simplificatrices (formes de vie, guildes écologiques) permettaient d'évaluer aussi bien le niveau en nutriment que des indices diatomiques basés sur les espèces. Ces métriques apportent des informations supplémentaires en termes de structure de biofilm qui ne sont accessible aux données en espèce. Enfin, la pollution des rivières par les micropolluants devient une préoccupation sociétale croissante. Nous avons émis l'hypothèse que les diatomées pouvaient être de bons candidats pour évaluer la pression en herbicides. Quatre expérimentations de 2 mois ont été réalisées en mésocosmes lotiques. Nous avons montré que les diatomées vivant entourées de matrices polysaccharidiques épaisses étaient plus résistantes aux pesticides dissous. Au contraire les diatomées présentant une surface cellulaire de contact importante avec l'eau étaient défavorisées. Ce type de métrique pourrait être utilisé in situ à plus large échelle. Nous concluons sur l'intérêt d'intégrer ces métriques à la bioindication par les diatomées. Mais également nous soulignons l'importance de croiser la phylogénie et l'écologie pour mieux comprendre quelles pressions environnementales ont forcées les diatomées à s'adapter. Si ces pressions peuvent être reliées à des pressions anthropiques, la bioindication par les diatomées en sera améliorée. / Diatoms are ubiquitous microalgae of an extreme diversity. This made them good indicators of aquatic ecosystems quality and they are used since 50 years for this purpose. Since year 2000, the European Water Framework Directive requires their use to assess the ecological quality of watercourses. A typological framework has to be used in order to compare comparable rivers between each other, that is, rivers of the same bioclimatic regions, flowing on the same geological substrate at similar altitudes. Various ecoregional classifications were defined on the basis of these parameters. We showed at a scale covering 4 countries (Spain, France, Italy and Switzerland) and at a regional scale (north-east France) that ecoregions and geology are determinant to explain communities. Parameters characterizing pollution were less important. Unlike some authors, we did not observe any homogenization of the communities when pollution level was increasing. Moreover, we did not observe geographically restricted communities: this would enable to aggregate ecoregions geographically distinct but presenting the same physical characteristics. Diatoms display a very important specific diversity which can be a problem for their routine use. We showed that when increasing determination precision (from sub-division to species), pollution assessment performances were increasing but much less than the number of taxa. Assessment performances between genus and species are similar anyway, whereas there are ten time more species than genera. We also showed that using simplifying metrics (life-forms, ecological guilds) enable assessing nutrient level as well as diatom indices based on species. These metrics bring additional information about biofilms structure that is not available with species data. At last, micropollutants pollution in rivers is of increasing concern to citizens. We hypothesized that diatoms could be good candidates to assess herbicide pressure. Four experiments lasting 2 months were conducted in lotic mesocosms. We showed that diatoms surrounded by thick exopolysaccharid matrices were more resistant to dissolved pesticides. On the over hand, diatoms presenting an important cell surface contact with water were disadvantaged. This kind of metric could be used in situ at a larger scale. We conclude on the interest to integrate such metrics to diatom bioassessment. But we also strength the importance to cross phylogeny and ecology to better understand which environmental pressure forced diatoms adapt. If these pressures can be related to anthropogenic pressures, diatom bioassessment will be improved.

A contribuição deste trabalho é apresentar uma metodologia de avaliação de risco ecológico do ambiente aquático utilizando-se dados provenientes de programas de monitoramento ambiental. O estudo tem como cenário um trecho do Rio Jacuí, município de São Jerônimo – RS, Brasil, que foi avaliado através da aplicação de um programa de monitoramento ambiental. Consideraram-se como variável explicativa deste estudo, as evidências registradas nos compartimentos abióticos, água superficial e sedimento. As evidências químicas foram decorrentes da presença dos metais Hg, Pb e Zn e as evidências ecotoxicológicas de ensaios de toxicidade aquática com Ceriodaphinia dubia para água superficial e Hyalella azteca para sedimento. Consideraram-se como variáveis respostas as evidências biológicas compostas pelos dados de riqueza, índice de Shannon-Weaver, equitatividade e densidade numérica das espécies das comunidades zooplantônica e bentônica. O risco ecológico (Baixo, Médio e Alto) foi caracterizado pela associação à qualidade ambiental (Ótima, Alerta e Crítica), respectivamente, estabelecida pelas evidências registradas. Os resultados permitem considerar que é possível o uso de programas de monitoramento ambiental para avaliação de risco ecológico, se contiverem, além dos dados químicos e ecotoxicológicos exigidos pela legislação ambiental, dados do monitoramento da biota residente. / The contribution of this work is to present a methodology for ecological risk assessment in an aquatic environment using data derived from environmental monitoring programs. The location focused by this study was a segment of the Jacuí River, in the town of São Jerônimo – RS, Brazil, which was assessed by applying an environmental monitoring program. The evidence recorded from the abiotic compartments surface water and sediments was considered an explanatory variable. The chemical evidence stemmed from the presence of Hg, Pb and Zn, while the ecotoxicological evidence resulted from aquatic toxicity tests using Ceriodaphinia dubia for surface water and Hyalella azteca for sediments. The biological evidence from the Shannon-Weaver index, species richness, equitability and numerical density data in zooplanktonic and benthonic communities was considered the response variable. The ecological risk (Low, Medium, and High) was characterized by the association with environmental quality (Great, Warning, and Critical), established by the evidence recorded. The results have shown that it is possible to use environmental monitoring programs to evaluate of ecological risk assessment, if they have chemical and ecotoxicological data required by environmental laws, and monitoring data of resident biota.

L’ichtyofaune est encore peu utilisée en bioindication sur les plans d’eau, alors que la demande des gestionnaires est forte, notamment dans le contexte de la mise en œuvre de la Directive Cadre Européenne sur l’Eau. L’objectif de cette thèse est d’analyser la réponse de l’ichtyofaune à diverses pressions anthropiques, afin de définir des variables biologiques de bioindication et construire un indice rendant compte de l’état écologique des lacs naturels et des retenues français. Plusieurs questions sont successivement abordées.En première analyse, les possibilités de sélection de métriques répondant à des pressions s’exerçant sur le bassin versant sont explorées par une approche typologique. L’analyse consiste à effectuer des classifications des plans d’eau, puis à établir, au sein de chaque groupe homogène d’un point de vue environnemental, des régressions linéaires entre les métriques candidates et les pressions. Les résultats montrent la pertinence de l’ichtyofaune en bioindication sur ces milieux, mais mettent en exergue des limites à cette approche typologique. Ainsi, afin de tester la possibilité de construction d’un bioindicateur commun aux lacs naturels et aux retenues, une méthode alternative dite « site spécifique » a ensuite été développée. Une modélisation statistique a été appliquée pour contrôler l’effet de l’environnement naturel sur les communautés piscicoles lacustres. Cette analyse montre que les métriques piscicoles répondant aux pressions sont différentes entre les deux types de milieux. La dernière étape, explique le développement d’un indicateur, construit sur le principe de la mesure d’un écart à la référence, en se basant sur une approche de type statistique par hindcasting. Cette méthode encore peu utilisée permet de s’affranchir de la sélection de sites de référence en France en modélisant les conditions biologiques de référence, i.e., telles qu’elles seraient en l’absence de pression anthropique. Les caractéristiques des communautés piscicoles des sites non perturbés sont ensuite comparées à celles des sites plus ou moins impactés par des pressions anthropiques. Ont été considérées ici les pressions s’exerçant à l’échelle du bassin versant et localement sur les plans d’eau. Suivant ce protocole, un indice poisson lacustre issu de la combinaison de métriques répondant conjointement à des pressions anthropiques globales et locales est proposé pour les lacs naturels et pour les retenues.Les avancées de ce travail et les perspectives sont ensuite discutées au regard du contexte européen de la gestion des milieux aquatiques. / Fish communities remain underused in the domain of lentic ecosystem bioindication, even though water managers need such tools in the current context of the Water Directive Framework. The objective of this thesis was to analyse the fish communities’ response to various anthropogenic pressures, in order to define the candidate biological variables in bioindication and to develop an index to evaluate the ecological status of French natural lakes and reservoirs. Several questions are raised.First of all, the means available to select fish-based metrics responding to catchment-scale anthropogenic pressures are analysed using a typological approach. This analysis consists in classifying lentic ecosystems using classifications, and then, within each homogenous group of ecosystems identified based on environmental criteria, performing linear regressions between candidate fish-based metrics and anthropogenic pressures. The results clearly show that fish communities could be used as good bioindicators for the lentic ecosystems, but they also underline the limits of typological approaches.To test how a bioindicator shared by natural lakes and reservoirs could be developed, an alternative site-specific method was subsequently developed. Statistical modeling was applied to control the natural environmental effects on lentic fish communities. This analysis shows that fish-based metrics responding to catchment-scale anthropogenic pressures differ in the two types of lentic ecosystems.The last part reports the development of an index, based on the reference condition approach, using a hindcasting statistical approach. This method, still infrequently used, enables one to sidestep the problem related to the selection of reference sites in France. Furthermore, this method allows modeling biological reference conditions, i.e. conditions without anthropogenic pressures. Fish communities’ characteristics are then compared for both undisturbed sites and sites that are more or less impacted by anthropogenic pressures. Both catchment-scale and local anthropogenic pressures were considered in this analysis. Following this protocol, a lake fish-based index resulting from the combination of metrics that respond jointly to global and local anthropogenic pressures was developed for natural lakes and reservoirs. Finally, the advances made as a result of this research and its perspectives are discussed with regards to the European context of aquatic ecosystem management.