Water is polluted by increasing activities of population and the necessity to provide them with goods and services that use water as a vital resource. The contamination of water due to heavy metals (HMs) is a big concern for humankind; however, global studies related to this topic are scarce. Thus, the current review assesses the content of HMs in surface water bodies throughout the world from 1994 to 2019. To achieve this goal, multivariate analyses were applied in order to determine the possible sources of HMs. Among the analyzed HMs in a total of 147 publications, the average content of Cr, Mn, Co, Ni, As and Cd exceeded the permissible limits suggested by WHO and USEPA. The results of the heavy metal pollution index, evaluation index, the degree of contamination, water pollution and toxicity load showed that the examined water bodies are highly polluted by HMs. The results of median lethal toxicity index showed maximum toxicity in As, Co, Cr and Ni in the surface water bodies. Results of ingestion and dermal pathways for adults and children in the current analyzed review showed that As is the major contaminant. Moreover, Cr, Ni, As and Cd showed values that could be considered as a high risk for cancer generation via the ingestion pathway as compared to the dermal route. It is recommended that remediation techniques such as the introduction of aquatic phytoremediation plant species and adsorbents should be included in land management plans in order to reduce human risks.

Water stress in Mediterranean countries is the result of both variable and changing climatic conditions and widespread anthropogenic pressures. Evrotas, an intermittent river located in Southern Greece, was used as a case study to assess the impacts of water stress on Mediterranean lotic ecosystems. Based on hydrological analyses, it was revealed that during prolonged drought years, such as the summers of 2007 and 2008, the vast majority of the Evrotas riverbed was completely desiccated, primarily as a result of substantial water abstraction for irrigation. The effects of desiccation on the riverine ecosystem were evaluated using fish and macroinvertebrate assemblages according to the demands of the Water Framework Directive 2000/60/EC (WFD). Faunal responses to water stress were assessed through comparisons of assemblages attributes in perennial and intermittent reaches and pre-drought versus postdrought communities. Effects of hydrological disturbance on fish species richness, density, percentage composition and size structure were more pronounced in intermittent than in perennial sites. The most obvious and immediate impact was the elimination of populations in the intermittent reaches. However, upon flow resumption, the recolonisation from upstream perennial reaches began, thereby permitting partial re-establishment of the depleted fish communities. Nevertheless, the structural integrity of fish communities remained severely impacted and recovery was markedly slow. On the contrary, post-drought macroinvertebrate assemblages were not affected by summer droughts, and the recruitment processes were rapid after flow resumption. Our findings point to the necessity of establishing a distinction between naturally and artificially driven intermittent rivers. We, therefore, propose the introduction of an ''artificially intermittent Mediterranean river'' condition within the context of the WFD assessment applications.

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Heteroptera species were collected from 48 sites distributed throughout the mainland and island complexes of Greece during 1999Greece during -2004. The aims of this study were to investigate Heteroptera distribution and abundance in Greek streams, identify the environmental factors that are linked to variation in their assemblages and to partition the influence of environmental and spatial components, alone and in combination, on Heteroptera community composition. Canonical ordination techniques (CCA) were used to determine the relationship between environmental variables and species abundance, while variation partitioning was performed using partial CCA to understand the importance of different explanatory variables in Heteroptera variation. Heteroptera variation was decomposed into independent and joint effects of local (physicochemical variables, microhabitat composition, stream width and depth), regional (land use/cover) and geographic variables (longitude, latitude, altitude and distance to source). Land use/cover, aquatic and riparian vegetation, stream size and water chemistry were the most important factors structuring Heteroptera assemblages. At regional scale, bug assemblages were mainly divided into those found in forested and agricultural landscapes, following water quality and microhabitat composition at local scale. Local variables accounted for 48% of the total explained variation, regional variables for 20% whereas geographical position appeared to be the least influencing factor (8.5%). The results of partial constraint analyses suggested that local variables play a major role in Heteroptera variation followed by regional variables.