Anthropogenic risk assessment of riverine habitat using geospatial modelling tools for conservation and restoration planning: a case study from a tropical river Pranhita, India.

The riverine ecosystem provides multiple benefits to human community and contributes to the sustainable development of the ecoregion. The growing dependency on these ecosystems has largely contributed to aggravating the ecological risks, habitat degradation, and loss of ecosystem services. The present study evaluates the ecological risk emanating from nine anthropogenic stressors including river use, hydro-morphology, catchment pollution, and biological stressor on river Pranhita in Godavari Basin of Peninsular India using InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) Habitat Risk Assessment model. The primary field survey, remote sensing, and secondary data-assisted spatial modelling results revealed low ecological risk (R = 0.65 of 3) in river Pranhita due to anthropogenic activities. Sediment loading, the inflow of nitrogen, and habitat fragmentation were the major stressors with relatively higher risk score (> 1); influence on a sizeable portion of riverine habitat (29-75% of the total area under high-risk zone) indicates the mounting threat from catchment activities. The low-risk value observed in protected river reaches as compared to unprotected areas is likely to be influenced by the abundant presence of intact riparian vegetation which mitigate the catchment stressors and minimal anthropogenic activity within protected areas. This study demonstrates the application of InVEST HRA model for ecological risk assessment of riverine ecosystems and fish assemblages along with their input data generation framework. This has the potential for prioritization of sensitive habitats based on computed ecological risk and stressor identification based on their exposure and consequences for developing appropriate mitigation measures. This model is spatially explicit and accommodates user-defined criteria for ecosystem-level assessment at a regional and national scale to facilitate the resource managers and policymakers for conservation and restoration planning and implementation of targeted management measures for sustainable development.

Applications of Sentinel-2 satellite data for spatio-temporal mapping of deep pools for monitoring the riverine connectivity and assessment of ecological dynamics: a case from Godavari, a tropical river in India (2016-2021).

Rivers are dynamic ecosystems with diverse habitats that require ample connectivity to ensure the flow of ecosystem services, thus empowering the sustainable development of an entire basin. Geo-spatial tools offer powerful prospects for monitoring of aquatic ecosystems. The usefulness of Sentinel-2 datasets to assess river connectivity has been explored for an un-gauged seasonal river system. The present study was undertaken in five ecologically unique river reaches viz. Wainganga, Wardha, Pranhita, Godavari-mid and Manair in Godavari Basin in the Indian Deccan Plateau to map water spread dynamics at various time scales, i.e., fortnightly, monthly, seasonal, annual and demi-decadal during 2016-2021. The maximum value of perennial water spread per square kilometre of total floodplain area (2016-2021), determined using Sentinel-2 imageries, was observed in river Wardha (0.18) followed by Pranhita (0.12) and Wainganga (0.11). The water spread showed a decreasing trend, while the number of patches in the river corridor increased over time from post-monsoon to pre-monsoon season. The copious perennial habitat with relatively larger patches, incessant flow in river Pranhita and obstructed flow, large-sized patches reported in river Wardha during summer months, hold importance in terms of providing refuge to aquatic biota. This study provides evidence for the impact of water projects on spatio-temporal water spread dynamics in Godavari Basin. The demonstrated utility of Sentinel-2 imagery coupled with gauge station measurements for river continuity assessment and deep pool mapping would aid in enhancing our understanding on environmental flow at a spatial scale, which in turn would aid in effective river management to achieve the Sustainable Development Goals. The implications of this study for sustainable environmental management and limitations are also discussed.

Biomarkers-based assessment of triclosan toxicity in aquatic environment: A mechanistic review.

Triclosan (TCS), an emergent pollutant, is raising a global concern due to its toxic effects on organisms and aquatic ecosystems. The non-availability of proven treatment technologies for TCS remediation is the central issue stressing thorough research on understanding the underlying mechanisms of toxicity and assessing vital biomarkers in the aquatic organism for practical monitoring purposes. Given the unprecedented circumstances during COVID 19 pandemic, a several-fold higher discharge of TCS in the aquatic ecosystems cannot be considered a remote possibility. Therefore, identifying potential biomarkers for assessing chronic effects of TCS are prerequisites for addressing the issues related to its ecological impact and its monitoring in the future. It is the first holistic review on highlighting the biomarkers of TCS toxicity based on a comprehensive review of available literature about the biomarkers related to cytotoxicity, genotoxicity, hematological, alterations of gene expression, and metabolic profiling. This review establishes that biomarkers at the subcellular level such as oxidative stress, lipid peroxidation, neurotoxicity, and metabolic enzymes can be used to evaluate the cytotoxic effect of TCS in future investigations. Micronuclei frequency and % DNA damage proved to be reliable biomarkers for genotoxic effects of TCS in fishes and other aquatic organisms. Alteration of gene expression and metabolic profiling in different organs provides a better insight into mechanisms underlying the biocide's toxicity. In the concluding part of the review, the present status of knowledge about mechanisms of antimicrobial resistance of TCS and its relevance in understanding the toxicity is also discussed referring to the relevant reports on microorganisms.

Assessment of mutagenic, hematological and oxidative stress biomarkers in liver of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in response to sublethal verapamil exposure.

The influx of pharmaceutical drugs and their metabolites have been reported to cause negative impact on aquatic biota. In this study, effects of long-term exposure of verapamil on mutagenic, hematological parameters and activities of the oxidative enzymes of Nile tilapia, Oreochromis niloticus were investigated for 60 days exposure at the concentrations of 0.29, 0.58 and 1.15 mg L-1 in the fish liver. The exposure resulted in significantly high (p < 0.05) micronuclei induction of peripheral blood cells at the peak on day 30 at 1.15 mg L-1. Compared with the control, there was significant increase (p < 0.05) in white blood cell counts and red blood cell distribution width (RDW), with a reduction in hemoglobin (Hb), red blood cell counts (RBCs), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) level as the concentration of the drug increased. The indices of oxidative stress biomarkers (lipid peroxidation and carbonyl protein) showed elevated level, depicting a positive correlation with both time and concentration. More so, the activity of energy-related parameter (Na+ -K+- ATPase) in the tissue was significantly inhibited (p < 0.05) at the end of 60 days exposure period. Further, the activity of catalase (CAT) was inhibited while reduced glutathione (GSH) level was decreased in the liver tissue. There was increase in the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) after 30 days at 0.29 mg L-1. The study demonstrated that prolonged exposure to verapamil at sublethal concentration can result in mutagenic effects and oxidative dysfunctions in O. niloticus.

Assessment of mangroves from Goa, west coast India using DNA barcode.

Mangroves are salt-tolerant forest ecosystems of tropical and subtropical intertidal regions. They are among most productive, diverse, biologically important ecosystem and inclined toward threatened system. Identification of mangrove species is of critical importance in conserving and utilizing biodiversity, which apparently hindered by a lack of taxonomic expertise. In recent years, DNA barcoding using plastid markers rbcL and matK has been suggested as an effective method to enrich traditional taxonomic expertise for rapid species identification and biodiversity inventories. In the present study, we performed assessment of available 14 mangrove species of Goa, west coast India based on core DNA barcode markers, rbcL and matK. PCR amplification success rate, intra- and inter-specific genetic distance variation and the correct identification percentage were taken into account to assess candidate barcode regions. PCR and sequence success rate were high in rbcL (97.7 %) and matK (95.5 %) region. The two candidate chloroplast barcoding regions (rbcL, matK) yielded barcode gaps. Our results clearly demonstrated that matK locus assigned highest correct identification rates (72.09 %) based on TaxonDNA Best Match criteria. The concatenated rbcL + matK loci were able to adequately discriminate all mangrove genera and species to some extent except those in Rhizophora, Sonneratia and Avicennia. Our study provides the first endorsement of the species resolution among mangroves using plastid genes with few exceptions. Our future work will be focused on evaluation of other barcode markers to delineate complete resolution of mangrove species and identification of putative hybrids.

Assessment of DNA damage and molecular responses in Labeo rohita (Hamilton, 1822) following short-term exposure to silver nanoparticles.

The increasing application of silver nanoparticles (Ag-NPs) both in industries and in agricultural fields has led to its accumulation in the aquatic ecosystem through water run-off. In the present study, the effects of Ag-NPs in the liver of Labeo rohita, were investigated at genomic and cellular level for seven days at the concentrations of 100, 200, 400 and 800 µg l(-1) by using 18 and 29 nm sizes of Ag-NPs. The Ag-NPs sizes of 18 and 29 nm were synthesized by a chemical method using atomic force microscopy with the zeta potential of -55 mV and-31.4 mV respectively. They were found to be spherical with smooth surfaces. Assessment of genotoxic effects of the particles in the fish using single-cell gel electrophoresis showed DNA damage on exposure to concentrations of 400 and 800 µg l(-1). Histopathological examination of the liver revealed vacuolar degeneration, hepatocytes have undergone total degeneration and high accumulation of Ag-NPs that depicted both time and dose-dependent relationships. Furthermore, the expression study of stress-related genes showed down-regulation, due to the production of free radicals and reactive oxygen species. Ag-NPs can cause both DNA damage and affect the cellular responses of L. rohita.