Search

The year 2022 was characterised by significant water shortages and droughts in Italy, with the most pronounced impact observed in the North-Western regions, including Piemonte. In conditions of water scarcity, treated wastewater undergoes little dilution by natural flows and this can deeply affect the chemistry of water-poor rivers and streams. However, increased pollution by wastewater would be partially offset by fast photodegradation of pollutants in shallow water and by the longer time allowed to photochemical reactions if water flows more slowly. We assessed the latter phenomena in the Stura di Lanzo, a middle-order Alpine river tributary of the largest Italian river, the Po, and affected by a wastewater treatment plant (WWTP). In 2022, the concentration values of the photochemically significant parameters nitrate, nitrite, and DOC were usually higher downstream of the WWTP outlet, which could slightly favour indirect photodegradation reactions. Direct and indirect photodegradation was assessed for the non-steroidal anti-inflammatory drugs paracetamol, diclofenac, and naproxen, all undergoing rather fast photoreactions. Photochemistry model results show that the three compounds would undergo 10-40 % photodegradation in spring and summer along the stretch separating the wastewater outlet from the confluence of Stura into the Po. Photodegradation would continue in the latter, but other WWTPs might contribute additional pollution in the meanwhile. Albeit significant, photodegradation could only partially promote the elimination of the contaminants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Globally, excessive fine sediment (particles <2 mm) deposition is acknowledged to have deleterious effects on aquatic biodiversity. However, the impacts are often equivocal possibly reflecting landscape context, although this is rarely considered. To address this, we examined the temporal response of macroinvertebrate taxonomic and functional diversity to experimental fine sediment clogging in a prealpine (Italy) and lowland setting (UK). Colonisation devices were installed insitu with either clean or clogged substrates and examined for short (7-14 days), medium (21-28 days) and long (56-63 days) timescales. Clogging resulted in altered taxonomic community composition in both the lowland and prealpine rivers and modified functional community composition in the prealpine river. Nestedness was consistently found to be the dominant process driving differences in taxonomic composition between the clean and clogged substrates in the prealpine environment, with clogged substrates forming a nested community. No dominant component structured lowland taxonomic communities. Functional community composition was driven by nestedness in both environments but was heavily dominant in the case of the prealpine river, possibly reflecting low functional redundancy. Widely employed community richness metrics (EPT, taxa and functional richness) only displayed a response to fine sediment loading in the prealpine environment but taxa characterized as sensitive to fine sediment as well as some functional feeding groups did exhibit differences in both settings. In the prealpine environment, the effects of fine sediment intensified over time for several community metrics. Although further research is required to corroborate our findings and extend our observations across more rivers and typologies, excessive fine sediment is a pervasive stressor affecting macroinvertebrate communities in prealpine and lowland environments. However, the biodiversity facets that responded to clogging differed between the two landscape settings probably reflecting wider environmental filtering. Monitoring and managing fine sediment loading likely requires context specific approaches to maximise ecological benefits., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Global patterns of biodiversity have emerged for soil microorganisms, plants and animals, and the extraordinary significance of microbial functions in ecosystems is also well established. Virtually unknown, however, are large-scale patterns of microbial diversity in freshwaters, although these aquatic ecosystems are hotspots of biodiversity and biogeochemical processes. Here we report on the first large-scale study of biodiversity of leaf-litter fungi in streams along a latitudinal gradient unravelled by Illumina sequencing. The study is based on fungal communities colonizing standardized plant litter in 19 globally distributed stream locations between 69°N and 44°S. Fungal richness suggests a hump-shaped distribution along the latitudinal gradient. Strikingly, community composition of fungi was more clearly related to thermal preferences than to biogeography. Our results suggest that identifying differences in key environmental drivers, such as temperature, among taxa and ecosystem types is critical to unravel the global patterns of aquatic fungal diversity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Clogging, the streambed colmation by fine sediments, is an important widespread source of impact affecting freshwaters. Alterations in stream morphology and hydrology, added to the effects of global climate change, are responsible for this phenomenon, that is particularly pernicious in mountainous lotic systems naturally characterized by coarse substrates. Among the studies investigating this issue some were descriptive, while others used artificial substrates to compare ongoing fine sediment accumulation and macroinvertebrate assemblage recruitment. Other studies used from the outset artificial substrates arranged with different levels of clogging. Our study fits into this line, but adding an innovative element simulating different availability of coarse particulate organic matter, i.e. the main trophic input in low-order, mountainous stream. To investigate how clogging and CPOM can influence macroinvertebrate communities, we placed 135 artificial substrates in the upper Po river (NW Italy). We set up a three way factorial design with three different levels of sedimentation and terrestrial leaf material. Artificial substrates were removed on three different dates. Benthic invertebrates were identified and classified according to their bio-ecological traits. We also measured macroinvertebrate dry mass and CPOM degradation in the different trap types. Our findings show that clogging acts as a selective filter influencing taxa richness, density, functional composition and biomass of benthic assemblage. Moreover, fine sediments affect the energetic dynamics in the river ecosystem, decreasing the mass loss rate of terrestrial leaves. Interestingly, our results clearly demonstrate that high availability of CPOM can buffer the negative effect of clogging, suggesting that an adequate input of allochthonous organic matter may lessen the impact of fine sediment deposition. Because land use transformation and removal of wooded riparian areas increase clogging and simultaneously reduces the input of CPOM, our findings stress the importance to include the management of river basins in the conservation strategies of mountainous streams., (Copyright © 2017. Published by Elsevier B.V.)

In this work, the sensitivity of a battery of tests on the social amoeba Dictyostelium discoideum has been assessed within a freshwater toxicity study. The results obtained from the evaluation of survival and replication rate of D. discoideum were compared to those derived with a series of widely used tests for freshwater toxicity assessment, i. e. bioassays using Vibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata. The effects on sublethal endpoints, i.e. lysosomal membrane stability (LMS) and endocytotic rate, were analysed in conjunction with high-level endpoints to verify the potential to make a typical bioassay more sensitive. The field ecotoxicological investigation employing D. discoideum is part of a monitoring study assessing environmental quality of the Bormida River (Italy), subjected until recently to a chronic industrial pollution. The survey was carried out at several stations (upstream and downstream of a chemical factory outlet) in two different periods. In 2002, the results of chemical analyses performed on river water indicated no contamination. The ecotoxicological data obtained in this period showed that no evidence of biological effects was observed using V. fischeri and D. magna bioassays. In spite of the previous classical acute toxicity tests, significant differences in cell viability of D. discoideum were found. By analysing the effects measured on LMS and endocytotic rate, more relevant changes were observed for these sublethal stress biomarkers compared to survival. The chronic toxicity data showed significant changes in cell growth both of P. subcapitata and D. discoideum. Nevertheless, more sensitive and rapid responses were obtained when assessing the effects of exposure on D. discoideum. The chemical and ecotoxicological data obtained in 2006 indicated a full recovery of the quality of the river water (neither contamination nor toxicity found). Altogether, the results reported in this study underline that the use of a battery of biomarkers in conjunction with high-level endpoints may help follow the pollutant-induced stress syndrome in the organisms from early sublethal effects to starting mortality.