Water quality assessments provide essential information for protecting aquatic habitats and stakeholders downstream of mining sites. Moreover, mining companies must comply with environmental quality standards and include public participation in water quality monitoring (WQM) practices. However, overarching challenges beyond corporate environmental responsibility are the scientific soundness, political relevance and harmonization of WQM practices. In this study, a mountainous watershed supporting large-scale gold mining in the headwaters, besides urban and agricultural landuses at lower altitudes, is assessed in the dry season. Conventional physicochemical and biological (Biological Monitoring Water Party-Colombia index) freshwater quality parameters were evaluated, including hydromorphological and land-use characteristics. According to the indicators used, water quality deterioration by mining was absent, in contrast to the effects of urban economic activities, hydromorphological alterations and (less important) agricultural pollutants. We argue that mining impacts are hardly captured due to the limited ecological knowledge of high-mountain freshwaters, including uncharacterized mining-specific bioindicators, environmental baselines and groundwater processes, as well as ecotoxicological and microbial freshwater quality components. Lessons for overcoming scientific and operational challenges are drawn from joint efforts among governments, academia and green economy competitiveness. Facing a rapid development of extractive industries, interinstitutional and multidisciplinary collaborations are urgently needed to implement more integrated freshwater quality indicators of complex mining impacts.

Aim:We studied the distribution of freshwater macroinvertebrate taxa and traits to distinguish ecological gradients among the mining-controlled and natural headwaters, and rural and urban economic activity influences.Location: In 2016's dry season, macroinvertebrate samples were collected at 40 locations in the Mashcon watershed, northern Peruvian Andes. Six locations were in the headwaters directly influenced by mining, eight near-pristine tributary headwaters, 14 agricultural locations at midstream and 12 urban locations downstream.Methods: Eight traits (five biological and three ecological) were selected according to data availability, and modalities scores were assigned using the weighted and the dominant-trait approaches. The traits relative abundances and abiotic conditions were compared among watershed sections. The ecological interpretability of the ungrouped data was verified with a distance-based redundancy analysis. Results:The high-altitude mining section had fewer taxa types and abundance, and distinct body forms distributions and prevalent body sizes in macroinvertebrate communities, relatable to the control of the mining headwaters. Physiological and ecological traits (respiration, mobility and attachment, food sources, feeding habits, saprobity and pH preferenda) differed among traits quantification approaches and were less informative at high altitudes. The ecological conditions from the near-pristine tributaries recovered in the vegetated midstream section, to again be affected in the downstream urban section.Main Conclusions: Our results suggest the presence of ecological impairment despite the excellent physicochemical quality of the water discharged by the mine. The obtainment of autecological information at a higher taxonomic resolution, e.g. for ubiquitous taxa like Acari and Chironomidae, would be needed to advance the freshwater quality assessment of ecologically and hydrogeochemically complex Andean mining ecosystems.

Peru is one of the megadiverse countries worldwide, displaying a great diversity of ecosystems due to its tropical location, marine currents, and complex relief, which jointly define environments differentiated by altitude and climatic conditions. The arid and semi-arid ecosystems comprising xeric and Andean shrublands, coastal deserts, and coastal hills, illustrate this diversity of ecosystems; these stretch over 177 358 km2, representing 13.8% of the Peruvian territory. Several studies on aquatic macroinvertebrates are being conducted in these ecosystems; although not so numerous yet, have shown a rise in recent years. The objective of this work was to determine the composition and distribution of aquatic macroinvertebrates in the arid and semi-arid ecosystems of Peru. To this end, we conducted a literature survey; the articles and theses found were reviewed and analyzed. The following keywords were used: macroinvertebrates, macrozoobenthos, bioindicators, diversity of aquatic organisms, and water quality; we used the Google Academic search engine, Scopus, Web of Science, ResearchGate and the thesis repositories of Peruvian universities, additionally a thesis from the University of Barcelona. Of a total of 53 sources of information, 38 are theses and 15 are scientific articles conducted from 1992 to 2020, referring to studies conducted at elevations ranging from 0 to 3,831 m asl. Most studies were conducted at the Lima and La Libertad departments, resulting in 20 and 10 publications, respectively. The topics addressed most frequently were bioindication, biodiversity, taxonomy, and distribution. Most theses were carried in the Universidad Nacional de Trujillo and the Universidad Nacional Mayor de San Marcos, with 12 and 10 theses, respectively. The period 2011–2020 records the largest number of publications (40). According to the type of aquatic ecosystem, rivers (38) were the systems most intensively studied, followed by coastal wetlands (14) and lagoons (2); to note, one thesis studied two types of ecosystems. Specimens were collected mainly with the Surber and D nets; as a result, seven phyla, 10 classes, 39 orders, and 118 families were reported. The highest richness of families corresponds to rivers (110), followed by coastal wetlands (57), and lagoons (12). The western hydrographic slope recorded the highest richness at phylum, class, order, and family levels, likely because most investigations were conducted in this slope. On the other hand, the phyla Cnidaria, Nematoda, and Nematomorpha were not recorded in the eastern slope, which showed fewer orders (19) relative to the western slope (39). A similar trend is observed at the family level: of the 118 families recorded, 59 were reported for the eastern slope. The most common families at both sides were Chironomidae, Baetidae, Simuliidae, Elmidae, Hydrophilidae, Libellulidae, Physidae, Dytiscidae, Ceratopogonidae, Coenagrionidae, Hydroptilidae, Hydropsychidae, and Tipulidae. Separately, the most common families in all types of aquatic ecosystems were Chironomidae, Baetidae, and Dytiscidae. It is recommended to further promote studies on macroinvertebrates living in the eastern slope, addressing taxonomic, and ecological topics, as well as broadening the approach to an integral ecosystem view. Finally, the biotic indices should be calibrated and validated for the main hydrographic basins. This work is an initial effort to review, systematize, analyze, and gather the results of studies on aquatic macroinvertebrates in Peru, particularly in arid and semi-arid ecosystems.