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Transport of hydrophobic pollutants in rivers such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals is often facilitated by suspended sediment particles, which are typically mobilized during high discharge events. Suspended sediments thus represent a means of transport for particle related pollutants within river reaches and may represent a suitable proxy for average pollutant concentrations estimation in a river reach or catchment. In this study, multiple high discharge/turbidity events were sampled at high temporal resolution in the Globaqua River Basins Sava (Slovenia, Serbia), Adige (Italy), and Evrotas (Greece) and analysed for persistent organic pollutants such as PAHs (polycyclic aromatic hydrocarbons) or PCBs (polychlorinated biphenyls) and heavy metals. For comparison, river bed sediment samples were analysed as well. Further, results are compared to previous studies in contrasting catchments in Germany, Iran, Spain, and beyond. Overall results show that loadings of suspended sediments with pollutants are catchment-specific and relatively stable over time at a given location. For PAHs, loadings on suspended particles mainly correlate to urban pressures (potentially diluted by sediment mass fluxes) in the rivers, whereas metal concentrations mainly display a geogenic origin. By cross-comparison with known urban pressure/sediment yield relationships (e.g. for PAHs) or soil background values (for metals) anthropogenic impact - e.g. caused by industrial activities - may be identified. Sampling of suspended sediments gives much more reliable results compared to sediment grab samples which typically show a more heterogeneous contaminant distribution. Based on mean annual suspended sediment concentrations and distribution coefficients of pollutants the fraction of particle facilitated transport versus dissolved fluxes can be calculated.

The hydrological and biological complexity of temporary rivers as well as their importance in providing goods and services is increasingly recognized, as much as it is the vulnerability of the biotic communities in view of climate change and increased anthropogenic pressures. However, the effects of flow intermittency (resulting from both seasonal variations and rising hydrological pressure) and pollution on biodiversity and ecosystem functioning have been overlooked in these ecosystems. We explore the way multiple stressors affect biodiversity and ecosystem functioning, as well as the biodiversity-ecosystem functioning (B-EF) relationship in a Mediterranean temporary river. We measured diversity of benthic communities (i.e. diatoms and macroinvertebrates) and related ecosystem processes (i.e. resource use efficiency-RUE and organic matter breakdown-OMB) across a pollution and flow intermittency gradient. Our results showed decreases in macroinvertebrate diversity and the opposite trend in diatom assemblages, whereas ecosystem functioning was negatively affected by both pollution and flow intermittency. The explored B-EF relationships showed contrasting results: RUE decreased with higher diatom diversity, whereas OMB increased with increased macroinvertebrate diversity. The different responses suggest contrasting operating mechanisms, selection effects possibly driving the B-EF relationship in diatoms and complementarity effects driving the B-EF relationship in macroinvertebrates. The understanding of multiple stressor effects on diversity and ecosystem functioning, as well as the B-EF relationship in temporary rivers could provide insights on the risks affecting ecosystem functioning under global change.

Trichonis Lake is the largest natural freshwater body in Greece with a surface area of 97 km2. It receives pollutants from numerous anthropogenic activities, especially from intensive agricultural practices, urban sewages, stock grazing land and small industries. In this study, hydrologic and chemical parameters are assessed during two periods (1990–1991) and (2001–2002) to evaluate the effects of the climatic changes on phosphorous trends and consequently on the trophic status of Trichonis Lake. Even though large quantities of fertilizers are applied in the lake's catchment, phosphorus loads are still in the permissible level as estimated according to Vollenweider's relationship based on total phosphorus concentration. Due to relatively higher rainfall precipitation during the last years, an increased amount of the phosphorus entering into the lake system is flushed out, thus keeping the trophic status of the lake in oligotrophic levels. In contrast, lower rainfall rates during the first period (1990–1991) have led to the decrease in phosphorus flush out and its detainment into the lake water and sediment resulting to mesotrophic conditions. As the trophic status of the lake is mainly hydrologically dependent and thus unpredictable, effective management plans targeting the elimination of nutrient pollution loadings are necessary.