M. Teresa Ferreira

Structural and functional responses of riparian vegetation to human disturbance: performance and spatial scale-dependence

Successful protection, enhancement and management of surface inland waters require bioassessment and monitoring of ecological quality, as recognized by the Water Framework Directive (WFD; EU/2000/60). In the present paper, we aimed at assessing the response to disturbance of structural and functional components of the riparian ecosystem in order to develop a plant-based index of biotic integrity (Riparian Vegetation index, RVI). Further, the implications of Mediterranean conditions and the spatial scale dependency in the index performance and its component metrics were investigated and discussed. Aquatic and bankside plant species were sampled at more than 400 sites of Portuguese rivers, in Spring-Summer of 2004 and 2005. Over 300 plant attributes were pre-screened to select 32 candidate metrics. Both single stressors and composite stressor indices were used in this study. Two spatial scale-approaches were evaluated: the Local River Type - LRT - which follows the Portuguese river typology, and the Regional River Type - RRT -, which clusters the LRT into North and South types. Compo- sition (e.g. cover and number of alien and endemic species) and functional metrics associated with life cycle and reproduction (e.g. numbers of perennial species), or with trophic status (e.g. proportion of nitrophyllous species) were the most responsive to disturbance across types. Overall, the RVI displayed a reliable response to disturbance; although the local approach has a higher discriminatory effi ciency, the macro scale approach had a more consistent response to multifaceted human disturbances and a more robust performance, essential for environmental-decision making. Results substantiate the hypothesis that plant-based indices of integrity are scale-dependent, an important consideration in the development of typological-adapted methods either for the WFD implementation or for other assessment and monitoring purposes. Future work is required to calibrate the index for inter-annual variability in plant structure and composition, which is especially relevant in Mediterranean-type rivers.

Invasibility patterns of knotgrass (Paspalum distichum) in Portuguese riparian habitats.

Spatial patterns of the exotic riverine knotgrass (Paspalum distichum L.) were examined in Mediterranean river basins in Southwestern Iberia. The major goals of this study were to assess the degree of invasibility of riparian habitats by this species and to determine the influence of environmental factors and human-induced disturbances that this knotgrass has on both the landscape and the habitat scales. The present study demonstrates the ability of knotgrass to invade riparian habitats in Portuguese freshwater ecosystems. However, most of the spatial variation of the knotgrass cover seemed to be driven by local factors, such as fine sediment enrichment and the fragmentation of riparian woods, and by other anthropogenic interferences in relation to both the fluvial system and the surrounding landscape. Nomenclature: Knotgrass, Paspalum distichum L. #3 PASDS. Additional index words: Exotic species, human disturbances, environmental variables, PASDS, Mediterranean basin.

Sensitivity of river fishes to climate change: The role of hydrological stressors on habitat range shifts.

Climate change will predictably change hydrological patterns and processes at the catchment scale, with impacts on habitat conditions for fish. The main goal of this study is to assess how shifts in fish habitat favourability under climate change scenarios are affected by hydrological stressors. The interplay between climate and hydrological stressors has important implications in river management under climate change because management actions to control hydrological parameters are more feasible than controlling climate. This study was carried out in the Tamega catchment of the Douro basin. A set of hydrological stressor variables were generated through a process-based modelling based on current climate data (2008-2014) and also considering a high-end future climate change scenario. The resulting parameters, along with climatic and site-descriptor variables were used as explanatory variables in empirical habitat models for nine fish species using boosted regression trees. Models were calibrated for the whole Douro basin using 254 fish sampling sites and predictions under future climate change scenarios were made for the Tamega catchment. Results show that models using climatic variables but not hydrological stressors produce more stringent predictions of future favourability, predicting more distribution contractions or stronger range shifts. The use of hydrological stressors strongly influences projections of habitat favourability shifts; the integration of these stressors in the models thinned shifts in range due to climate change. Hydrological stressors were retained in the models for most species and had a high importance, demonstrating that it is important to integrate hydrology in studies of impacts of climate change on freshwater fishes. This is a relevant result because it means that management actions to control hydrological parameters in rivers will have an impact on the effects of climate change and may potentially be helpful to mitigate its negative effects on fish populations and assemblages.

Modeling water quality in reservoirs used for angling competition: Can groundbait contribute to eutrophication?

Abstract Inland recreational fishing is a popular leisure activity in Portugal, which has close to 219,000 anglers. This study aimed to determine if the groundbait used to attract fish to the area in angling competitions contributes to eutrophication of reservoirs. We conducted a quantitative and qualitative assessment of commercial groundbait to examine the relationship between eutrophication and groundbaiting in angling competitions performed in Maranhão Reservoir, one of the most important southern Portugal angling reservoirs. Simulations using the CE-QUAL-W2 model were performed from January 2001 to February 2007 considering the number of anglers present in angling competitions and the chemical characteristics of commercial groundbait. The results indicated that the use of 5–10 kg of groundbait per angler (3–20 tons of groundbait per year) did not alter the ecological functioning of Maranhão Reservoir; however, higher angling pressures may lead to a significant increase in nutrient concentrations and consequent increases in primary production in the waterbody. Based on these concerns, we combined modeling with simulations to evaluate the environmental effects of groundbaiting in recreational angling and its relation to reservoir eutrophication. This study represents a contribution to more practical and holistic management of recreational fisheries.