Water quality evaluation of two urban streams in Northwest Uruguay: are national regulations for urban stream quality sufficient?

Innovative lake pollution profiling: unveiling pollutant sources through advanced multivariate clustering techniques

In many developed and developing nations, lakes are the primary source of drinking water. In the current scenario, due to rapid mobilization in anthropogenic activities, lakes are becoming increasingly contaminated. Such practices not only destroy lake ecosystems but also jeopardize human health through water-borne diseases. This study employs advanced hierarchical clustering through multivariate analysis to establish a novel method for concurrently identifying significantly polluted lakes and critical pollutants. A systematic approach has been devised to generate rotating component matrices, dendrograms, monoplots, and biplots by combining R-mode and Q-mode analyses. This enables the identification of contaminant sources and their grouping. A case study analyzing five lakes in Bengaluru, India, has been conducted to demonstrate the effectiveness of the proposed methodology. Additionally, one pristine lake from Jammu & Kashmir, India, has been included to validate the findings from the aforementioned five lakes. The study explored correlations among various physical, chemical, and biological characteristics such as temperature, pH, dissolved oxygen, conductivity, nitrates, biological oxygen demand (BOD), fecal coliform (FC), and total coliform (TC). Critical contaminants forming clusters included conductivity, nitrates, BOD, TC, and FC. Factor analysis identified four primary components that collectively accounted for 85% of the overall variance. Following identification of pollution hotspots, the study recommends source-based pollution control and integrated watershed management, which could significantly reduce lake pollution levels. Continuous monitoring of lake water quality is essential for identifying actual contaminant sources. These findings provide practical recommendations for maximizing restoration efforts, enforcing regulations on pollutant sources, and improving water quality conditions to ensure sustainable development of lakes.

Effects of urbanization and accessibility to sanitation services on water quality in urban streams in Uruguay

The world's urban population is growing rapidly, and threatening natural ecosystems, especially streams. Urbanization leads to stream alterations, increased peak flow frequencies, and reduced water quality due to pollutants, morphological changes, and biodiversity loss, known as the urban stream syndrome. However, a shift towards recognizing urban streams as valuable natural systems is occurring, emphasizing green infrastructure and nature-based solutions. This study in Uruguay examined water quality in various watersheds with different urbanization levels and socio-environmental characteristics along a precipitation gradient. Using Geographic Information Systems (GIS) and in situ data, we assessed physicochemical parameters, generated territorial variables, and identified key predictors of water quality. We found that urbanization, particularly urban areas, paved areas, and populations without sanitation, significantly influenced water quality parameters. These factors explained over 50% of the variation in water quality indicators. However, the relationship between urbanization and water quality was non-linear, with abrupt declines after specific urban intensity thresholds. Our results illustrate that ensuring sanitation networks and managing green areas effectively are essential for preserving urban stream water quality. This research underscores the importance of interdisciplinary teams and localized data for informed freshwater resource management.

Fish parasites as proxy bioindicators of degraded water quality of River Saraswati, India

The nature and intensity of water pollution determine the effects on aquatic biota and aquatic ecosystem health. The present study aimed at assessing the impact of the degraded physicochemical regime of river Saraswati, a polluted river having a historical legacy, on the parasitic infection and the role of fish parasite as a bioindicator of water quality. Two Water Quality Indices (WQIs) were adopted as useful tools for assessing the overall water quality status of polluted river based on 10 physicochemical parameters. Total 394 fish (Channa punctata) were examined. Ectoparasite Trichodina sp., Gyrodactylus sp., and endoparasites Eustrongylides sp. were collected from the host fish. Prevalence, mean intensity and abundance for each sampling period were calculated for the determination of parasitic load. The parasitic load of Trichodina sp. and Gyrodactylus sp. was significantly (p < 0.001) higher in winter, whereas the parasitic load of Eustrongylides sp. showed no significant (p > 0.05) seasonal fluctuation. The parasitic load of ectoparasites was negatively correlated with temperature, free carbon dioxide, biochemical oxygen demand, and WAWQI but positively correlated with electrical conductivity and CCMEWQI. Fish health was found to be adversely affected by degrading water qualities and parasitic infection. A 'vicious cycle' develops as a result of the interplay among deteriorating water quality, withering fish immunological defence, and amplifying parasitic infection. Since parasitic load was strongly conditioned by the combined influence of a suite of water quality parameters the fish parasites can be used as a powerful indicator of deteriorating water quality.

Incidence of Watershed Land Use on the Consumption of Meso and Microplastics by Fish Communities in Uruguayan Lowland Streams

Physical-chemical and biologicaldiversity of streams are influenced by the land use in their watersheds. Plastics currently make up the most important waste asset, representing an important part of the transported and accumulated material in water courses. This work analyzes the consumption of plastics debris by the fish communities in streams with two contrasting types of land use. We worked with threestreams impacted by urbanization and threeby extensive ranching. The stomach and intestinal contents of 309 individuals of 29 species were analyzed, by a modified alkaline digestion, and observed under a stereo microscope with polarized light. A total of 373 plastic itemswere found, of which the majority corresponded to fibers (318). A significant difference was found between the percentage of individuals that consumed plastic debrisbetween both systems (51.6% in ranchers and 76.6% in urban, p = 0.014 Mood’s Median), but no difference was found in the average ingested per individual. This study establishes the first baseline on plastic debris consumption by fish in Uruguayan streams, showing the extent of the plastic and microplastic pollution problem. Although there are differences between the analyzed sites, we also observed significant contamination in streams far from urbanization.