Douro River Basin Research Articles

Biotic homogenization as a threat to native affiliate species: fish introductions dilute freshwater mussel's host resources

AbstractAimThe indirect consequences of biotic homogenization, the process of a gradual increase in the similarity of regional biotas driven by the combined effects of species invasions and extinctions, are still poorly understood. In this study, we aimed to assess the ability of a native affiliate species to maintain its host resources under the condition of biotic homogenization of host communities.LocationCentral (Vltava River Basin, Czech Republic) and western (Douro River Basin, Portugal) Europe.MethodsWe tested the ability of non‐native species to serve as an alternative partner in local host–affiliate relationships. We used a European freshwater mussel, Anodonta anatina, which is considered to be a host generalist of native fish species, and compared the compatibility of its glochidia with native versus non‐native fishes in two distinct European regions. Subsequently, we projected the obtained host compatibility data into the recent progress of biotic homogenization and estimated the degree of host dilution.ResultsWe found significant differences in the ability of A. anatina glochidia to parasitize the native and non‐native fish species in both the central and peripheral parts of the mussel's distribution range. As a result, the increasing presence of non‐native species within fish communities across Europe likely significantly decreases the availability of the mussel's host. Biotic homogenization of host communities may interfere with general life history traits (host specificity) of their local affiliate species.Main conclusionsThis study demonstrates that the mixing of regional biotas may lead to an excessive loss of host availability even for host generalists, such as the freshwater mussel A. anatina, with potentially broad consequences for their population dynamics. Conservation strategies of endangered affiliate species need to incorporate the biogeographical context of host–affiliate relationships and particularly the consequences of biotic homogenization.

The Political Geography of Environmental Regulation: Implementing the Water Framework Directive in the Douro River Basin, Portugal

The article discusses the challenges and prospects of implementing the Water Framework Directive (WFD), one of the most comprehensive pieces of environmental legislationpassed by the European Union (EU). The translation of the WFD into policy-making is analysed through a case study – which combined interviews, participant observation and the attendance of public events – in the Portuguese section of the Douro River Basin. The evolution of water regulation is initially considered according to a suggested classification into five phases of water management. The examination then addresses the main aspects of the WFD experience in the Douro, exploring elements of innovation and continuity. Higher concern for environmental conservation and the detailed assessment of water management problems are significant improvements that followed the introduction of the WFD. However, the same institutional reforms have also served to consolidate techno-bureaucratic approaches centred on the economic values of water. As a result, the rationality and failures of the new water regulation prompted unexpected opposition from various stakeholder groups, such as farmers, non-governmental organisations (NGOs) and urban water customers. The success of the WFD is directly dependent on the ability to perceive the politicised complexity of water management and on effective mechanisms of dialogue and social inclusion.

Assessing the geochemical inherent quality of natural soils in the Douro river basin for grapevine cultivation using data analysis and geostatistics

The main purpose of this study is to measure the spatial variability of a specific soil characteristic, its content of nutrients and toxic metals, and use the established patterns of variability as an indicator of the inherent quality of the natural soils of the Douro river basin for grapevine cultivation. A total of 108 topsoil samples were collect within the basin catchment. All soil samples were analysed for 26 chemical elements by ICP-ES OPTIMA at ACME Anal. Lab. (ISO 9002 Accredited Co.). For this study, we selected only the chemical elements that are relevant for the vineyards, that is, elements that are nutrients or those which are potentially toxic. In our study we used the following methodology: (i) categorisation of quantitative variables and use of multiple correspondence analysis (MCA) to determine similarities among them; (ii) structural analysis through variography to identify spatial patterns of variability; (iii) mapping of MCA factors through ordinary kriging to define, within the basin, areas in which soils can be characterised according to their contents of nutrients or toxic elements. This methodology allows the determination of spatial patterns of variability for groups of similar variables instead of an exhaustive “one-by-one” variable study, since data analysis reduces the amount of information that must be interpreted in order to assess the natural aptness of the soils for grapes plantation.

Genetic introgression between wild and stocked brown trout in the Douro River basin, Spain

The genetic diversity of Spanish brown trout is currently threatened by stocking with exogenous brown trout from Central and Northern Europe. In the Douro River basin 25% of the analysed populations in the present study showed introgression by genes of hatchery origin. The mean introgression estimated by the single locus approach (S) varied from 0 to 22% among populations, with a mean value of 3%. The hatchery allele markers were absent in populations where stocking ceased in 1993. However, the introgression effect was observed in all populations stocked until 1998. It seems that cessation of stocking is a good measure for restoring native populations. A thorough review of published and present data of genetic interactions between wild and stocked brown trout in Spanish rivers indicates different levels of introgression between basins. The absence of a clear geographical pattern in the introgression level suggests that ecological interactions and local stocking programmes may play an important role in stocking success. Finally, several guidelines are provided for conservation and management of native brown trout populations in Spanish rivers.

Genetic introgression between wild and stocked brown trout in the Douro River basin, Spain

Genetic introgression between wild and stocked brown trout in the Douro River basin, Spain

Ecological impact of groundwater extraction on wetlands (Douro Basin, Spain)

Declining water table levels in the Douro River basin, Central Spain, are caused by the extraction of groundwater from a relatively homogeneous aquifer, and results in several types of impact on local wetlands which vary according to their characteristics. These wetlands are local, intermediate and regional groundwater discharge sites, seepages from post-Tertiary deposits, and non-linked ponds to groundwater dynamics. The following important factors influence the type of impact: the recharge or discharge nature of the affected sector of landscape; the type of connection with the regional aquifer; flow lengths and residence time of the water; the interaction between the water and the surface material, particularly clay. A wide range of wetland values and functions are affected according to the type of impact. These include productivity, amenity, recreational, scientific, educational and conservation values.

Landscape ecology of uncultivated lowlands in Central Spain

The relationship between groundwater and landscape in representative areas of the Spanish plateaux is discussed, with special attention given to the Douro River basin. The study focusses on the transference of water and matter that is conditioned by groundwater flow systems, and also on water bodies, wet meadows, marshes, saline soils under their influence. These factors are of great importance in semiarid areas. Using photointerpretation, interviews, vegetation plots, water samples from wells and springs and soil samples, and the results of data processing (principal component analysis, shared information) we find that hydrological processes are the main controlling factor in the ecological function and variation of uncultivated lowlands. These processes include the alternation of recharge and discharge areas, the geochemical evolution of groundwater and the independent flows of the regional system. The landscapes in recharge and discharge areas are compared, as well as the influence of the evolutionary stage of the groundwater in the latter areas (glycophyte or halophyte vegetation). After observing the ecological importance of these aquifer discharges systems, the causes of their accelerated transformation are analyzed.