Ecological and human health risk from exposure to metal contaminated sediments in a subtropical river affected by anthropogenic activities: A case study from river Yamuna.

Heavy metal enrichment in river sediments poses a significant risk to human and aquatic health. The Yamuna River faces severe challenges due to untreated industrial and domestic wastewater discharge. The study evaluates sediment metal content, ecological and human health risks, and potential sources. Results showed Cd and Pb exhibited moderate to severe contamination and displayed ecological risk based on contamination factor, enrichment factor, and potential ecological risk. According to synergistic indices (pollution load index, PINemerow, toxic risk index, contamination security index, mean probable effects level quotients, and probability of toxicity), the sediment in the Yamuna River doesn't seem to have a risk or enrichment from combined metals. Cd and Pb mainly originate from anthropogenic sources. Hazard index (< 1) and carcinogenic risk (2.2 × 10-7 to 4.7 × 10-5) assessments suggest metal didn't pose any risk to humans exposed to sediment. The present study aids in developing pollution control strategies for the Yamuna River.

Fishery, growth, mortality, and stock assessment of endangered Tor putitora from Tehri dam reservoir, Uttarakhand, Himalayan foothills of India in relation to environmental variables.

The current study determined Tor putitora (Hamilton, 1822) fishery, growth, mortality, and population characteristics using length-frequency data assembled monthly from the Tehri dam reservoir in Uttarakhand from January to December 2022. The estimation data was separated into 40-mm class intervals, and population parameters were investigated and computed using the FiSAT-II software tool. W = 0.0101 L2.996, where a = 0.0101 and b = 2.99, were determined as the length-weight relationships, and the growth performance index (ϕ) was computed to be 5.40. Tor putitora commercial catches in the Tehri dam reservoir were dominated by length groups of 360-399 and 320-359 mm. Different growth parameters were estimated using length-frequency data as L∞ = 987.00 mm, K = 0.26 yr-1, and t0 = -0.0003 years. Z, M, and F mortality coefficients were estimated to be 1.01, 0.27, and 0.73, respectively. At the end of the first, second, third, fourth, fifth, sixth, and seventh years, the fish measured 226, 400, 535, 638, 718, and 780, and 827, respectively. The estimated value of the exploitation rate (E) was 0.73 using the length-converted catch curve approach, which was determined to be somewhat higher than the optimum value (0.50). Tor putitora recruitment patterns from the Tehri dam reservoir reveal that the species only has one recruitment pattern every year, and that solely occurs from June to September. The current exploitation level (0.73) has already exceeded the maximum fishing pressure (Emax = 0.508), indicating that there is a decline in the catch at the current fishing pressure, and a further increase in fishing efforts may lead to a decline in the stock, which may be detrimental to the sustainable fishery of Tor putitora in the Tehri dam reservoir, Uttarakhand, India.

Influence of barrages on hydrological parameters and functional groups of phytoplankton of a subtropical river Ganga, India.

The current study used phytoplankton functional groups (FGs) to assess the impact of barrages on the ecological function of subtropical river Ganga. A total of 101 phytoplankton species were identified, including 20 phytoplankton FGs with MP and D having the highest prevalence rates of more than 50%. Other FGs with higher occurrence rates, such as N, A, and J, displayed seasonal and spatial advantages on occasion, indicating the randomness of exogenous influx from catchment areas. Based on phytoplankton FGs similarities, a non-metric multidimensional scaling analysis (NMDS) revealed geographical and seasonal discrepancies. The higher concentration of chemical components in Kanpur was linked to decreased water discharged from preceding reservoirs, resulting in a highly polluted stretch in terms of spatial variation, according to our findings. During the monsoon season, however, the diluting process caused by precipitation and surface runoff significantly improved water quality. As a result, we hypothesized that a sequence of barrages alters the hydrological characteristics of cascading reservoirs, which was related to spatial and seasonal fluctuation in FG diversity and phytoplankton FGs could be useful bioindicators of water quality. In conclusion, the phytoplankton FGs approach is useful for identifying the geographical and seasonal aspects of aquatic ecosystems that are heavily influenced by human activities, but its sensitivity to changes in spatial and seasonal water quality warrants more exploration.

Impact of barrages on assemblage pattern of phytoplankton in tropical river Ganga, India.

The occurrence, abundance, and distribution of phytoplankton have been investigated upstream and downstream of three barrages on the river Ganga at Bijnor, Narora, and Kanpur in Uttar Pradesh, India. A total of 104 phytoplankton species belonging to eight phyla (Bacillariophyta, Charophyta, Chlorophyta, Cryptophyta, Cyanophyta, Euglenophyta, Miozoa, and Ochrophyta) were identified during the sampling period. During the summer, monsoon, and post-monsoon seasons, the density of phytoplankton (Ind. L-1) ranged from 9.6 × 104 to 2.03 × 107, 9.6 × 104 to 4.5 × 105, and 2.2 × 105 to 2.17 × 106, respectively. The species abundance and the relative abundance showed an increasing trend from the first (Bijnor) to the third (Kanpur) barrage, suggesting a gradual decrease in river flow and an increase in residence time. Phytoplankton cell density in Kanpur, however, was unexpectedly higher and showed eutrophic conditions attributable to elevated organic load and surplus nutrients from the land runoff. One-way ANOVA (post-hoc Tukey test) showed statistically significant (p < 0.05) seasonal variation in temperature, transparency, free CO2, PO43-, and dissolved organic matter. Analysis of Pearson's correlation coefficient suggested a statistically significant correlation (p < 0.05) of mostly phytoplanktonic groups with free CO2, CO32-, HCO3-, Cl-, specific conductivity, total dissolved solids, total hardness, Mg2+, PO43-, and SiO44-. The minimum species diversity was recorded during the monsoon season, while the maximum diversity was reported during the post-monsoon season which might be due to high nutrient load and a high concentration of PO43- post-monsoon. We concluded that aquatic biodiversity and ecological structure could be adversely influenced by a series of obstructed barrages and dams, which influenced the assemblage pattern of phytoplankton communities.

Genetic diversity and demographic history of the giant river catfish Sperata seenghala inferred from mitochondrial DNA markers.

The giant river catfish Sperata seenghala has huge demand in South Asian countries due to its low number of intramuscular bones and nutritive value. However, the culture practises for this fish have not been standardized and the current demand for this fish is being met by capture fisheries only. Unregulated and indiscriminate fishing would lead overexploitation of fish stocks subsequently stock depletion. Genetic diversity between populations would give insight about population structure and demography. In the present study, S. seenghala stocks from three rivers, namely Ganga, Brahmaputra and Mahanadi were characterized using cytochrome b gene and D-loop region. Moderate to high haplotype diversity and low nucleotide diversity values were observed in all populations. Analysis of molecular variance and pairwise FST values showed significant genetic differentiation among populations. Patterns of diversity, haplotype networks and mismatch distribution strongly suggest a historical influence on the genetic structure of S. seenghala populations. S. seenghala stocks from these three rivers are genetically distinct units and management measures should be formulated separately for each population.

A GFP-based bacterial biosensor with chromosomally integrated sensing cassette for quantitative detection of Hg(II) in environment.

A mercury biosensor was constructed by integrating biosensor genetic elements into E. coli JM109 chromosome in a single copy number, using the attP/attB recombination mechanism of lambda phage. The genetic elements used include a regulatory protein gene (merR) along with operator/promoter (O/P) derived from the mercury resistance operon from pDU1358 plasmid of Serratia marcescens. The expression of reporter gene gfp is also controlled by merR/O/P. Integration of the construct into the chromosome was done to increase the stability and precision of the biosensor. This biosensor could detect Hg(II) ions in the concentration range of 100-1700 nmol/L, and manifest the result as the expression of GFP. The GFP expression was significantly different (P < or = 0.05) for each concentration of inducing Hg(II) ions in the detection range, which reduces the chances of misinterpretation of results. A model using regression method was also derived for the quantification of the concentration of Hg(II) in water samples.