Tesis doctoral de Belinda Gallardo Armas
In europe and north america, up to 90% of floodplains have become extensively regulated, occupied, and polluted, with important consequences in the floodplain structure and functionality. The response of this ecosystem to human alteration is complex and its study is of great relevance in the development of management plans to effectively counteract the influence of negative human impacts. To address these needs, the present study provides a solid background for river-floodplain restoration through the investigation of the response of aquatic communities, especially macroinvertebrates, to changes in hydrological connectivity, environmental factors and human pressure across the floodplain of a mediterranean system, the middle ebro river (ne spain). our results showed how the lateral hydrological connectivity is the key factor structuring the habitats and aquatic communities of the middle ebro floodplain. This hydrological connectivity was related to a wide variety of environmental processes affecting directly and indirectly the presence of aquatic organisms, from habitat re-organization to nutrient transport. Moreover, hydrological connectivity explained at least one third of the macroinvertebrate species and trait composition, and more than half of the observed variability in the abundance and richness of macroinvertebrates, zooplankton and phytoplankton. Turbidity, salinity and nutrient status were secondary drivers, although essential for understanding the adaptation of aquatic communities to the floodplain environmental variability. On the other hand, the present study allowed identifying surrogates of hydrological fluctuations that were useful to assess the abundance, richness and composition of aquatic communities. For instance, the macroinvertebrate community depended on the duration of the connections established between each wetland and the river channel, whereas organisms with short life-cycles, like phytoplankton and zooplankton, responded better to water-level fluctuations. the combination of hydrological connectivity and environmental variability create a spatio-temporal template for the aquatic community that enables predictions about the taxonomic and functional patterns more likely to occur under particular conditions. According to the ebro template (a) frequently flooded habitats, as the river channel and adjacent wetlands, were dominated by insects and aquatic worms that showed disturbance resistance (e.G., Small body-shape, protection of eggs) and resilience (e.G., Short life-span, asexual reproduction) abilities, (b) by contrast, confined wetlands that are rarely flooded, including oxbow lakes, were dominated by non-insect taxa, as crustaceans and gastropods, showing the ability to interact with other organisms (e.G., Large size, sexual reproduction), as well as to effectively use habitats and resources (e.G., Diverse locomotion and feeding strategies), (c) the combination of habitat heterogeneity and nutrient availability under intermediate hydrological conditions resulted in highest macroinvertebrate species and trait diversity and, (d) the abundance and richness of three different groups of organisms (zooplankton, phytoplankton and macroinvertebrates) peaked at increasing levels of hydrological connectivity (flooded during 5, 30 and 40 days yr-1 respectively). in the middle ebro river, progressive regulation of river flow has altered the natural river-floodplain interaction. Consequently, there are very few possibilities of new wetlands creation, while the diversity and functionality of the remaining ones are threatened by the limited hydrological connectivity. The objective of river-floodplain restoration in the middle ebro river should thus consist in re-establishing a wide range of wetland types in accordance with the river-floodplain potential for ecological sustainability. In order to achieve this, a number of actions can be positively performed, such as the modification of embankments, the re-connexion of isolated floodplain habitats, the creation of new wetlands, the recovery of unproductive areas of the floodplain and the control of the water quality at a catchment scale.
Datos académicos de la tesis doctoral «Aquatic community patterns across environmental gradients in a mediterranean floodplain and their application to ecosystem restoration«
- Título de la tesis: Aquatic community patterns across environmental gradients in a mediterranean floodplain and their application to ecosystem restoration
- Autor: Belinda Gallardo Armas
- Universidad: Girona
- Fecha de lectura de la tesis: 10/07/2009
Dirección y tribunal
- Director de la tesis
- Francisco A. Comín Sebastian
- Tribunal
- Presidente del tribunal: María del rosario Vidal abarca gutierrez
- isabel Muñoz gracia (vocal)
- sylvie Tomanova (vocal)
- María Luisa Suárez alonso (vocal)