Adjusting the effect of seasonal variability in the bioassessment of streams.

Bioassessment tools should distinguish between the effects of anthropogenic degradation in communities and natural temporal changes. The present study tests the influence of natural seasonal variability on macroinvertebrate stream communities assessed by a predictive model (PORTRIV) and a multimetric index (IPtI) calibrated for spring. The scores of PORTRIV decreased significantly between spring and autumn, and between spring and winter (ca. 37 to 53%, respectively), while those of IPtI did not change significantly between seasons. For non-reference samples, the results of the predictive model also indicate no significant differences. A correction factor (CF) was calculated to adjust the existing differences in the model assessments between seasons, based on the percentage of variation of reference site scores from spring to autumn and winter. After the application of the CF to the OE50 scores of spring reference samples, the differences were no longer significant. Independent reference validation sites confirmed this tendency. This method has the advantage of avoiding large efforts required for the construction of databases from other seasons and the development of new models to allow the assessment of streams in seasons other than spring. Further tests with models developed in regions with more marked seasonal changes should be done to confirm its wider applicability.

Effect of environmental education on the knowledge of aquatic ecosystems and reconnection with nature in early childhood.

Blue and green ecosystems are considered a key for the improvement of cities sustainability, providing numerous ecosystem services and habitat for many species. However, urban streams are still neglected and degraded, specially in southern European countries. One important step towards the rehabilitation of these ecosystems is the awareness of their importance by citizens. This study aimed to assess the effect of 1-year of activities (field and laboratory) of an environmental education project on primary school children, in improving their knowledge on urban stream ecosystems and their problems. We analyzed students' questionnaires before and after field and laboratory activities, drawings and group interviews. Initially, most children had incipient contact with rivers and streams, showing fears and lack of knowledge about them. As the project progressed, their perceptions changed, with a clear increase in the proportion of students recognizing the biodiversity associated to rivers (e.g., names of riparian trees, aquatic plants and invertebrates). Also, their fears decreased significantly, while their awareness to the impacts of artificialization and lack of riparian vegetation increased. Our results show that direct contact with nature have a positive role in the way it is understood by children, as well as promoting responsible and sustainable behaviors, being effective from the early primary-school years.

Influence of river regulation and instream habitat on invertebrate assemblage' structure and function.

Dams modify geomorphology, water quantity, quality and timing of stream flows affecting ecosystem functioning and aquatic biota. In this study, we addressed the structural and functional macroinvertebrate community alterations in different instream mesohabitats of two Portuguese rivers impaired by dams. We sampled macroinvertebrates in riffles, runs and pools of river sites downstream of the dams (i.e. regulated; n = 24) and in sites without the influence of the dams (i.e. unregulated; n = 7), assessing a total of 64 mesohabitats, following late spring-early summer regular flows. We found a distinct taxonomic structure and trait composition of macroinvertebrate assemblages between regulated and unregulated flow sites, and also between mesohabitats in which the differences were more evident. When analysing each mesohabitat individually, the effect of flow regulation was detected only in run-type mesohabitats for both taxonomic and trait composition, leading us to infer that a selective macroinvertebrate assessment on run mesohabitats would be a valuable contribution to detect regulated flow effects on ecosystems impaired by dams. Additionally, there is evidence that respiration and locomotion traits could be effective tools to identify damming flow alterations. This study supports that the quality assessments of rivers impacted by dams could benefit from a sampling approach focused on run mesohabitats and the detection of some key traits, which would improve assessment accuracy.

Sewage contamination under water scarcity effects on stream biota: biofilm, grazers, and their interaction.

One of the most common anthropogenic impacts on river ecosystems is the effluent discharge from wastewater treatment plants. The effects of this contamination on stream biota may be intensified in Mediterranean climate regions, which comprise a drought period that leads to flow reduction, and ultimately to stagnant pools. To assess individual and combined effects of flow stagnation and sewage contamination, biofilm and gastropod grazers were used in a 5-week experiment with artificial channels to test two flow velocity treatments (stagnant flow/basal flow) and two levels of organic contamination using artificial sewage (no sewage input/sewage input). Stressors' effects were determined on biofilm total biomass and chlorophyll (Chl) content, on oxygen consumption and growth rate of the grazers (Theodoxus fluviatilis), and on the interaction grazer-biofilm given by grazer's feeding activity (i.e., biofilm consumption rate). The single effect of sewage induced an increase in biofilm biomass and Chl-a content, simultaneously increasing both grazers' oxygen consumption and their feeding activity. Diatoms showed a higher sensitivity to flow stagnation, resulting in a lower content of Chl-c. Combined stressors interacted antagonistically for biofilm total biomass, Chl-b contents, and grazers's feeding rate. The effect of sewage increasing biofilm biomass and grazing activity was reduced by the presence of flow stagnation (antagonist factor). Our findings suggest that sewage contamination has a direct effect on the functional response of primary producers and an indirect effect on primary consumers, and this effect is influenced by water flow stagnation.