Pollution impacts on water bugs (Nepomorpha, Gerromorpha): state of the art and their biomonitoring potential

Aquatic insects for monitoring the health status of riverine potholes: A case study in Chalakudy river basin, Kerala, India

Potholes are microhabitats in riverine ecosystems that substantially contribute to the unique regional faunal diversity and community composition. Investigations on the ecological status of potholes in riverine habitats are very scanty. The present work is of utmost importance, particularly as a pioneering study to evaluate the health status of riverine potholes using aquatic insects as potential biological indicators. Samples of water and aquatic insects were collected and analyzed during the pre-monsoon season from February 2022 to May 2022 in the potholes at Athirappilly and the Ezhattumugham regions of the Chalakudy river basin. The present study identified 208 individuals represented by 15 families in the potholes at Athirappilly, whereas 94 individuals belong to 10 families at Ezhattumugham. The computation of water quality parameters and benthic metrics revealed a significant variation between the stations. Spearman correlation analysis revealed that the water temperature, electrical conductivity, dissolved oxygen concentration, and biochemical oxygen demand were influencing the distribution of aquatic insects in the potholes. Families such as Perlidae, Ephemeridae, Baetidae, Stenopsychidae, and Hydropsychidae (sensitive families) reported from the well-oxygenated potholes at Athirappilly, where the water temperature and biochemical oxygen demand were minimum. The significantly high percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and a low family biotic index value indicate good health condition of the potholes at Athirappilly. In contrast, the low percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and high family biotic index values, with the abundance of tolerant families (Micronectidae, Caenidae, and Chironomidae), reflect the impact of organic pollution at Ezhattumugham.

Using Sentinel-2 data to estimate the concentration of heavy metals caused by industrial activities in Ust-Kamenogorsk, Northeastern Kazakhstan

This study aims to investigate the change in heavy metal concentration and evaluate pollution intensity using Sentinel-2 data. Sixty samples collected from the surface soil in the area were used to determine the concentration of lead, copper, and zinc using atomic absorption spectroscopy. Then, the step-by-step regression method was used in ArcGIS software to determine the relationship between the concentration of heavy metals and the ranking of the influential spectral bands of Sentinel-2 to monitor heavy metals in the relevant sampling points. According to the results, lead monitoring was effective through the blue channel, the ratio of green to near infrared-IV channels, and the ratio of short-wave infrared-III to near infrared-II channels. At the same time, copper was monitored through reflectance values in the red channel, the ratios of green to near infrared-IV channels, and the ratio of short-wave infrared-III to near infrared-II channels. The blue channel and the ratio of green to near infrared-IV channels the ratio of near infrared-II to near infrared-IV channels were efficient for zinc monitoring. Pollution Load Indices (PLI) and Geographical Accumulation Index (Igeo) were calculated to classify the contaminated soils of the region. The efficiency of each relationship obtained was evaluated using the root mean square error (RMSE) and Pearson's correlation coefficient (R). In summary, the copper, lead, and zinc equations had RMSE values of 1.8, 2.5, and 1.60 mg/kg, respectively. The Pearson correlation coefficients (R) for copper, lead, and zinc were 0.80, 0.76, and 0.72, respectively, which indicated good agreement between measured and estimated values.

Effects of Different Types of Agricultural Land Use on the Occurrence of Common Aquatic Bugs (Nepomorpha, Heteroptera) in Habitats with Slow Flowing Water in Bulgaria, Southeast Europe

Agricultural activities can have a significant impact on aquatic organisms, including aquatic insects. Most of the aquatic Heteroptera are known as moderately tolerant to low oxygen and high nutrient concentrations. Nevertheless, the complex effects of agriculture (source of both pesticides and nutrient loads) on this group are still unclear. Therefore, the relationship between six agricultural land use classes and the occurrence of common aquatic bugs in Bulgaria was studied. In order to avoid detection bias, presence-only models were applied; Maxent algorithm was used. According to the results, land use practices connected to arable land (annual crops) have stronger influence on the occurrence of the selected aquatic Heteroptera species than those connected to perennial crops (vineyards and fruit trees). Higher sensitivity to the effects of agriculture was indicated for species preferring microhabitats without macrophyte vegetation, Aphelocheirus aestivalis (Fabricius, 1794) and Micronecta griseola Horváth, 1899, compared to species preferring macrophyte dominated sites, Nepa cinerea Linnaeus, 1758, Ilyocoris cimicoides (Linnaeus, 1758) and Sigara striata (Linnaeus, 1758).

Effects of Pesticides on the Survival of Shredder Nectopsyche sp. (Trichoptera) and Leaf Decomposition Rates in Tropical Andes: A Microcosm Approach

Andean streams are becoming increasingly impacted by agricultural activities. However, the potential effects of pesticides on their aquatic biodiversity remain unassessed. In order to address this knowledge gap, we conducted an experiment over 37 days in microcosms to assess the effect of two pesticides commonly used in Ecuador (Engeo and Chlorpyrifos) on the aquatic insect Nectopsyche sp. (Trichoptera: Leptoceridae) at 0, 0.10, 5 and 10 μg L^-1 concentrations. The highest concentration corresponds to the maximum concentration allowed by the Equatorian legislation. We assessed insect mortality every 24 h, with leaf litter decomposition rates of organic matter determined by deploying Andean alder (Alnus acuminata) dry leaf packs in the microcosms. We found significant mortality of Nectopsyche sp. at high concentrations of Chlorpyrifos, whereas leaf litter was not significantly affected by any of the treatments. We conclude that the environmental legislation of Ecuador might not be fully protecting aquatic biodiversity from pesticide pollution. Further studies are needed, especially when considering that the maximum permitted concentration is very likely exceeded in many areas of the country. We also suggest that the maximum permissible values should be reviewed, considering each pesticide individually.