Zugl.: Konstanz, Univ., Diss., 2005

University, Diss., 2004--Kiel.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 6 uppsatser.

Les diatomées sont des micro-algues largement utilisées pour évaluer la qualité écologique des milieux aquatiques. La grande majorité des indices biotiques utilisant les diatomées sont basés sur la sensibilité à la pollution des espèces. Cela constitue un frein à leur utilisation car l’identification taxonomique au niveau de l’espèce est complexe, longue, coûteuse et source d’erreurs. Afin de rendre le processus d’identification plus simple, des indices biotiques basés sur des niveaux taxonomiques supérieurs à l’espèce, comme le genre, ont été mis au point. Mais la perte d’informations associée à la réduction de la résolution taxonomique est susceptible de rendre ces outils moins efficaces.Une approche alternative et plus récente propose de baser la simplification, non pas sur la taxonomie, mais sur la phylogénie. Cette approche fait implicitement l’hypothèse qu’il existe un signal phylogénétique dans les préférences écologiques des espèces, c’est à dire que deux espèces phylogénétiquement proches sont davantage susceptibles de présenter des réponses écologiques similaires que deux espèces prises au hasard. Si un tel signal existe, il implique une possible redondance phylogénétique dans les outils de bioindication existants, en particuliers ceux basés sur les niveaux taxonomiques les plus fins. L’objectif est de mettre à profit ce signal pour simplifier l’évaluation écologique des milieux aquatiques.Ce travail s’attache à développer cette approche chez les diatomées et se décompose en trois parties. Nous présentons d’abord un nouveau package R entièrement dédié à l’analyse du signal phylogénétique et à l’étude de la distribution des valeurs de traits dans les phylogénies. Nous démontrons ensuite la présence d’un signal phylogénétique pour de nombreux traits écologiques chez les diatomées d’eau douce. Ces traits sont les optimums écologiques de 127 espèces pour un ensemble de paramètres physico-chimiques, mesurés pendant huit ans dans des cours d’eau de l’est de la France. Nous montrons que le signal est variable en fonction des traits mais que la niche écologique des espèces étudiées est, de manière générale, dépendante de la phylogénie. Dans une troisième partie, nous proposons une méthode pour extraire des clusters d’espèces partageant des traits similaires tout en étant phylogénétiquement proches. Nous mettons en œuvre cette méthode sur des données de sensibilités aux pollutions pour démontrer les possibilités de simplification des indices biotiques basés sur les diatomées en prenant en compte la redondance phylogénétique. Nos résultats tendent à montrer que le potentiel de simplification en utilisant la phylogénie comme guide est significatif. / Diatoms are micro-algae commonly used to assess the ecological quality of freshwaters. Most of the biological indices using diatoms are based on species sensitivity to pollutions. This constitutes an obstacle to the use of diatoms in ecological assessment because taxonomical identification at species level is difficult, time consuming, costly and source of errors. To avoid this problem, scientists developed biological indices based on higher taxonomical levels like the genus. However, the loss of information caused by the taxonomical resolution decrease can make these methods less efficient.A more recent alternative proposes to use the phylogeny to simplify ecological assessment methods. This approach makes the implicit hypothesis that there is a phylogenetic signal for species ecological preferences, i.e. that closely related species are more likely to share similar ecological preferences than species taken randomly. If such a signal exists, it may mean that there is a phylogenetic redundancy in bioassessment tools, especially the ones which are based at species level. The aim is to exploit this signal to simplify the biological assessment of aquatic ecosystems.This work aims to develop this approach with diatoms and is divided in three parts. First, we introduce a new R package dedicated to the analysis of the phylogenetic signal and to study traits values patterns in phylogenies. In a second part, we demonstrate the presence of phylogenetic signal for many ecological traits in freshwater diatoms. These traits are the ecological optima of 127 species for a set of physical and chemical parameters. They were estimated from data collected during 8 years in rivers in eastern France. We show that the strength of the signal varied significantly from one trait to another but, overall, diatoms ecological niches are related to the phylogeny. Finally, in a third part, we introduce a new method to extract clusters of species sharing similar traits and being phylogenetically related. We apply this method on pollutions sensitivities data in order to demonstrate the possibility to simplify biological indices based on diatoms by taking account of phylogenetic redundancy. Our results suggest that phylogenetic approaches offer a scope for simplification without an important loss of ecological information.

<p>Seasonal changes in reproduction, recruitment, occurrence and growth of marine plant and animal species is a common phenomenon world-wide. This thesis investigates whether such seasonal changes could determine the succession in subtidal phytobenthic communities on free space in the Baltic Sea. My results showed circular seasonal patterns both in the settlement of species and in the annual appearance of communities. The circular seasonal pattern was also observed in the succession. Initial species assemblages were determined by the time space became available for colonisation. Although the succession seemed to be directed towards one site-specific final community structure determined by physical factors, the time of the year when space became available influenced the rate of the succession through species interactions. Rapid growth and timing of settlement and free space occurrence allowed early species to occupy all available space and prevent further colonisation, thereby slowing the succession. My results also showed that both settlement and community structure are influenced by substrate characteristics. Studying community development on vertical artificial structures revealed communities with few species and different composition compared to communities on vertical natural substrates. A field study showed that settlement and community structure changed significantly between 60º and 90º substrate slopes. This thesis shows that some differences in the final community structure are determined already at the settlement stage and that the succession pattern varies depending on when free space occurs. However, small inter-annual and site-specific differences in seasonal settlement periods and site-specific final communities mainly determined by physical factors, suggest that succession patterns are relatively predictable. Seasonal changes seem to cause a spiralling succession towards a final, seasonally undulating, state.</p>

Seasonal changes in reproduction, recruitment, occurrence and growth of marine plant and animal species is a common phenomenon world-wide. This thesis investigates whether such seasonal changes could determine the succession in subtidal phytobenthic communities on free space in the Baltic Sea. My results showed circular seasonal patterns both in the settlement of species and in the annual appearance of communities. The circular seasonal pattern was also observed in the succession. Initial species assemblages were determined by the time space became available for colonisation. Although the succession seemed to be directed towards one site-specific final community structure determined by physical factors, the time of the year when space became available influenced the rate of the succession through species interactions. Rapid growth and timing of settlement and free space occurrence allowed early species to occupy all available space and prevent further colonisation, thereby slowing the succession. My results also showed that both settlement and community structure are influenced by substrate characteristics. Studying community development on vertical artificial structures revealed communities with few species and different composition compared to communities on vertical natural substrates. A field study showed that settlement and community structure changed significantly between 60º and 90º substrate slopes. This thesis shows that some differences in the final community structure are determined already at the settlement stage and that the succession pattern varies depending on when free space occurs. However, small inter-annual and site-specific differences in seasonal settlement periods and site-specific final communities mainly determined by physical factors, suggest that succession patterns are relatively predictable. Seasonal changes seem to cause a spiralling succession towards a final, seasonally undulating, state.

Statistical modelling is often used to relate the presence or abundance of species to environmental predictors, thereby providing a basis for predictive mapping of species or biodiversity. The variables included must thus be relevant and reflect actual changes in the environment. Therefore, the quantification of species–environment relationships is an important aspect of predictive modelling. This thesis examines how phytobenthic species or communities in the Baltic Sea relate to environmental gradients, and if different aspects of phytobenthic species distribution in the Baltic Sea could be explained by spatial or temporal variation in environmental factors. Predictive distribution modelling usually focuses on how environmental variables control the distribution of species or communities. Thus the relative weight of the predictor variables on different scales is of importance. In this thesis, I show that the relative importance of environmental variables depends both on geographic scale and location, and that it also differs between species or species groups. There are no simple explanations to the temporal variability in species occurrence. I here show that the temporal changes in species distribution within the phytobentic zone varies in a spatial context. I also try to find temporal and spatio-temporal patterns in species distribution that could be related to changes in climate or anthropogenic disturbance. However, the findings in this thesis suggest that single factor explanations are insufficient for explaining large-scale changes in species distribution. A greater understanding of the relationship between species and their environment will lead to the development of more sensitive models of species distributions. The predictions can be used to visualise spatial changes in the distribution of plant and animal communities over time. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.

A system of pools arises in the upper part of the Lužnice river during the spring flood. This study describes inter-annual development of phytobenthos in the floodplain system of the Lužnice River, including temporary/permanent pools during spring flood.

En raison de leur importante capacité de réponse aux changements environnementaux, les producteurs primaires sont depuis longtemps utilisés comme indicateurs biologiques de la qualité des milieux aquatiques. La Directive Cadre Européenne sur l’Eau (2000/60/CE) préconise ainsi l’utilisation du phytoplancton, du phytobenthos et des macrophytes afin de mesurer l’état écologique des écosystèmes lacustres. Dans cette étude, ces trois compartiments ont été utilisés pour déterminer l’état écologique de cinq lacs localisés dans la région Aquitaine (Sud-Ouest de la France), lacs ayant la particularité de présenter des niveaux trophiques différents. Les résultats ont montré qu’au niveau intra-lac la composition floristique dépend fortement des variables physiques dans la plupart des systèmes tandis qu’au niveau inter-lac celle-ci dépend du niveau trophique. Le phytoplancton s’est révélé être l’indicateur de qualité le plus performant et le seul utilisable dans les eaux ouvertes, et le plus précis dans les systèmes où les macrophytes submergés étaient absents. Cependant, dans les lacs humiques, les assemblages phytoplanctoniques semblent répondre davantage à la turbidité et aux brassages fréquents de la colonne d’eau qu’aux nutriments. Dans de telles conditions, afin de mieux caractériser la qualité de l’eau, l’utilisation complémentaire du phytobenthos et des macrophytes se révèle plus pertinente. En conclusion, considérant les trois compartiments biologiques, la présente étude permet une approche complémentaire de l’état écologique des systèmes lacustres. Certaines des méthodes appliquées ici représentent un outil potentiel de détermination de la qualité de l’eau selon les exigences de la DCE, mais elles nécessitent d’être affinées pour une meilleure évaluation de l’état écologique des lacs français. Une attention particulière a été portée aux taxa exotiques observés dans ces lacs tempérés, et cet aspect doit être pris en considération lors de l’évaluation écologique. En effet, ces espèces sensiblement avantagées par les conséquences du changement climatique, peuvent altérer la structure et le fonctionnement des écosystèmes aquatiques en place, et aboutir à une perte de diversité. / Due to their important ability to respond to environmental changes, primary producers have been used for a long time as biological indicators of water quality. The Water Framework Directive (2000/60/EC) recommends the use of the phytoplankton, phytobenthos (diatoms) and macrophytes in the ecological status assessment of lakes. In this study, these three compartments have been used to determine the ecological status of five lakes located in the Aquitaine region (southwest of France) with different trophic status. The results showed that within lakes, the floristic composition in most of the systems strongly depends on physical parameters whereas among lakes it depends on the trophic status. The phytoplankton proved to be the most powerful indicator of quality in open-water areas as well as in systems where submerged macrophytes are absent. However, in the humic lakes, the phytoplankton assemblages seem to respond more to turbidity and mixing than to nutrient load. Under such conditions, water quality could be underestimated and the complementary use of phytobenthos and macrophytes appears more appropriated. In conclusion, considering the three biological elements, the present study allows a complementary approach of the ecological status of the lakes. Some of the methods applied here represent a potential tool for the assessment of the ecological status in the context of WFD, but they need to be refined to assess more properly the ecological status of French lakes. A special attention was paid to exotic taxa observed in these temperate lakes, and this aspect must be taken into account in the ecological assessment. Indeed, these species favoured by the consequences of the climate change, can modify the structure and functioning of the aquatic ecosystems, and lead to a loss of diversity.

Submitted by Carlos Augusto Rolim da Silva Junior (carlos_jrolim@hotmail.com) on 2015-11-24T14:47:46Z No. of bitstreams: 1 arquivototal.pdf: 2619104 bytes, checksum: de044ad4f4b291e30f7248f5a0b7e155 (MD5) / Made available in DSpace on 2015-11-24T14:47:46Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2619104 bytes, checksum: de044ad4f4b291e30f7248f5a0b7e155 (MD5) Previous issue date: 2014-01-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Reefs ecosystems have high biological diversity, but they have suffered many impacts resulting from human activities. These anthropogenic stressors may promote particular impacts on reef benthic communities, which are often structured by sessile organisms. Thus, knowledge about the community structure of phytobenthos have been used as the basis for the assessment of environmental impacts in many marine environments. In the case of reefs, changes in nutrient concentrations, as well as overfishing, have been described as the greatest responsible for the damages to the structure of this ecosystem. Thus, several studies have been conducted in order to better understand the role of herbivory and nutrient enrichment on the structure of seaweed communities. In this context, the present study was to analyze the patterns of colonization and succession of the phytobenthos, as well as the influence of herbivory, especially the reef fish on these processes. Thus, this study was divided into two chapters, the first being: "Assessment of patterns of colonization and succession of the phytobenthos in reef communities in Paraíba coast." The assay used artificial substrates, and was conducted within the boundaries of a marine reserve (Parque Estadual Marinho de Areia VermelhaPEMAV) and an adjacent location that has similar biotic characteristics; and showed that the colonization of different groups over time is probably related with biological characteristics of the species (life cycle, morphological structure and reproductive strategies). The second chapter, entitled " The influence of herbivorous fish species on patterns of colonization and succession of phytobenthos in reef ecosystems," indicates that the group of herbivores did not affect the structure of the phytobenthos community present in PEMAV, a situation which is possibly related to overfishing and degradation of the coastal reefs in Paraíba, which alter the structure of the fish and phytobenthic communities. / Os recifes formam ecossistemas que apresentam grande diversidade biológica e, no entanto, têm sofrido diversos impactos, resultantes de ações antrópicas. Estes estressores antropogênicos podem promover um impacto especial sobre as comunidades bentônicas dos recifes, que quase sempre são estruturadas por organismos sésseis. Desta forma, conhecimentos a respeito da estrutura das comunidades de fitobentos têm sido utilizados como base para a avaliação de impactos ambientais em muitos ambientes marinhos. No caso dos recifes, as alterações nas concentrações de nutrientes, assim como a sobrepesca, têm sido apontados como os maiores responsáveis pelo comprometimento da estrutura desse ecossistema. Assim, diversos estudos têm sido conduzidos com o propósito de compreender melhor o papel da herbivoria e do enriquecimento de nutrientes na estrutura das comunidades de algas marinhas. Neste contexto, o presente estudo se propôs a analisar os padrões de colonização e sucessão do macrofitobentos, bem como a influência da herbivoria, em especial pela ictiofauna, sobre esses processos. Desta forma, o presente trabalho foi dividido em dois capítulos, sendo o primeiro: “Avaliação dos padrões de colonização e sucessão do macrofitobentos em comunidades recifais do litoral paraibano”. O ensaio utilizou substratos artificiais e foi conduzido dentro dos limites de uma reserva marinha (O Parque Estadual Marinho de Areia Vermelha-PEMAV) e numa localidade adjacente que apresenta características bióticas semelhantes; e evidenciou que a colonização e sucessão dos diferentes grupos ao longo do tempo provavelmente está relacionada às características biológicas das espécies (ciclo de vida, estrutura morfológica e estratégias reprodutivas). Já o segundo capítulo, intitulado “A influência da ictoufauna herbívora sobre os padrões de colonização e sucessão do macrofitobentos em ecossistemas recifais”, verificou que o grupo dos herbívoros não atuou de maneira a afetar a estrutura da comunidade do macrofitobentos presente no PEMAV, o que provavelmente está relacionado à degradação dos recifes costeiros paraibanos, que acaba por alterar a estrutura das comunidades ícticas e fitobentônicas.