The effects of prevailing weather on short-term dynamics of certain water quality variables in low-flow conditions were studied in the Ganga river stretch at Allahabad, India. Mean temperature and light intensity showed general diel pattern with significant (p < 0.001) higher values in the afternoon, while significant high rate of change (p < 0.001) was observed in evening wind speed. Total dissolved solids (TDS), total suspended solids (TSS) and turbidity were quite high and displayed a general variable pattern significantly (p < 0.05) associated by evening winds. Wind speed exhibited a significant negative correlation with Chl-a and positive correlation with TSS (r2 = 0.48 and 0.74, p < 0.05, respectively). Afternoon temperatures affected the rate of change of water temperature which was also significantly correlated with dissolved organic carbon (DOC) (r2 = 0.79, p < 0.001). DOC was significantly correlated with the TDS levels (r2 = 0.80, p < 0.001). No correlation existed between average flow (9.50 ± 0.51 m3 s−1) and the tested water quality parameters, while it exhibited strong correlation with the water temperature (r2 = 0.89, p < 0.05). The results indicate that the low-flow conditions during summer may make the river water a complex turbid system where afternoon temperature and evening winds have significant influences on the short-term dynamics and may partially mask the general diurnal patterns of certain water quality variables. The study indicates complex interactions among weather and water quality parameters in low-flow conditions which warrant more elaborative studies. Constant monitoring is recommended to find out an optimum flow to reduce the chances of weather influenced pollution aggravation in this important river stretch.

The river Ganges, the National Heritage, and the lifeline of millions of Indians, unfortunately, ranked the second most polluted rivers of the world in 2017. This review reveals the current trends of the water quality of the Ganges assessed around 36 stretches during 2012–2016, to indicate an improvement around 6 (16.7%), deterioration around 14 (38.9%), and non-significant changes around 16 (44.4%) stretches. An increase in dissolved oxygen and a decrease in biochemical oxygen demand were observed at six stretches (Devprayag [S5], Rishikesh upstream [S7], Varanasi upstream [S19], Mokama upstream [S25], Mokama downstream [S26], and Munger [S27]). The total and fecal coliform contamination decreased at seven stretches (Rudraprayag [S2 and S3], Devprayag [S5 and S6], Rishikesh [S7], Varanasi upstream [S19], and Munger [S27]) due to improved hygienic conditions, but it increased subsequently at eight stretches (Haridwar [S8], Kanpur [S15], Raibareili [S16], Prayagraj [S17 and S18], Patna [S24], Berhampore [S30], and Serampore [S31]) due to improper defecation and mass bathing during 2007–2016. Dissolved oxygen level declined significantly, and biochemical oxygen demand increased (> 3 ppm), alarmingly at places receiving heavy untreated sewage water. The water quality of the Ganges was good up to Rishikesh, because of an undisrupted flow of the uncontaminated water from the higher altitudes (≥ 372 m) with higher forest cover, lower temperatures (< 21 °C), and higher dissolved oxygen (≥ 8.5 ppm) and due to the dissolution of antipathogenic chemical constituents of the medicinal herbs, pollutant degrading alkaline phosphatase, and bacteriophages. The present review is a systematic collection of data on river pollution, its scientific analyses, and its relationship with 6Ps (namely population, poverty, pollution, precipitation, plantation, and periodicity). Not only that, but the river water restoration measures have also suggested through the novel interlinked water working groups for implementing integrated water management strategies.

The Ganga River, which is one of the largest river systems of India with great ecological and social values, is under strong influence of multiple anthropogenic perturbations. Although a large number of monitoring and assessment programs has been initiated by the Government of India and other agencies, there is still a lack of studies explicitly considering ecosystem responses towards human-induced alterations in rivers. The present study was targeted to measure ecosystem responses towards metal pollution in the Ganga River. This study was conducted during summer low flow of the year 2019 at four study sites along 518 km middle segment of the Ganga River. The study shows that fluorescein diacetate hydrolytic activity (FDAase) in the bed sediment can be used as an ecosystem ‘response’ to carbon, nutrients and metal pollution in humanimpacted rivers. The FDAase activity showed dependence on substrates (carbon and nutrients) when the heavy metal concentrations were below the toxic threshold. We found a decrease in FDAase activity at Wpdr Site despite the presence of sufficient amount of carbon. This site is characterized by high concentration of total heavy metal (THM) and total bioavailable fraction (TBF) exceeding 360 μg g-1 and 174 μg g-1 respectively and able to induce negative response. The results of this study will help understanding the ecosystem responses towards human perturbations and planning management strategies for the Ganga River rejuvenation.

Almost all civilizations of the world are inextricably linked with rivers where all civilizations originated and developed [1]. Rivers in any means are enormously cherished and valued by all human communities due to their significant services on which human civilization’s survival is dependent [2]. However, nowadays due to many natural and anthropogenic pollution problems, the riverine ecosystems of the world are under great pressure which are affecting the deliverables of the river systems all over the world [3,4] (Table 1). Unplanned urbanization, changing land use patterns, intensified agricultural processes, huge hydroelectric power projects, heavy industrial use of waters, polluted effluent discharge, and contaminated runoffs are major contributing factors of pollution to these fresh water sources [5,6]. With these concerns, the climate change is another colossal crisis which is aggravating the problems of riverine ecosystem by increasing temperatures, altering rainfall-runoff patterns, and disrupting biological communities of river bodies which impart an imbalance to these ecosystems [7-9]. Numerous other indirectly related climate change stressors also increase the extent and magnitude of pollution problems and thus impacts become much wider along different dimensions of a river regime [10,11]. In consequence, many riverine ecosystems may totally collapse under these complex and unidentified impacts of climate change [4,12,13]. In its fifth assessment report, IPCC has projected 1.5-4.5°C increase in average global temperature (IPCC, 2013). The present assessment projects that, the globally averaged combined land and ocean temperature shows a warming of 0.89°C (0.69 to 1.08°C) over the period 1901-2012; with the rate of warming at 0.05°C (–0.05 to +0.15°C) per decade over the past 15 years (1998-2012). This report indicates the freshwater-related risks of climate change has also increased significantly where each degree of warming is projected to decrease renewable water resources by at least 20%. These trends and changes may intensify the problems of raw water quality by increasing water temperature; more loading of sediment, nutrient and pollutant due to abrupt and heavy rainfall; reduced dilution of pollutants during droughts, and unmanageable treatment facilities during floods [14-16].

The present study was undertaken to evaluate the effects of silver nitrate (AgNO3) and biosynthesized silver nanoparticle (AgNps) on Cucumis sativus L seedlings. Results indicated that both the forms of silver significantly reduced the growth which may be accompanied due to increased accumulation of silver in plants (4708.2 ± 108.75 mg/kg). Both the treatments showed steep reduction (> in AgNO3 treatments) in photosynthetic performance, total chlorophyll, carotenoids and total protein content and significantly (P < 0.05) increased oxidative stress (MDA, H2O2, SOR; i.e. > in AgNO3 treatment). The histochemical observations (NBT & DAB) of oxidative stress markers (H2O2 and O2−) were also in accordance with their total estimation of H2O2 and O2− in both the treatments. Chlorophyll florescence parameters were also significantly (P < 0.05) influenced by AgNO3 and AgNps treatments and showed remarkable modifications.Though, both the treatments (AgNO3 and AgNps) showed anatomical impacts on the root cortical cells, however, degeneration of cortical cells and disintegration of endodermis in AgNO3 treatments were more prominent. Taking impacts of the both forms of silver together, present study suggests that the AgNO3 is more toxic than AgNPs while potential risks of both forms is critical on the growth and development of Cucumis seedlings. We suggest further studies to explore the underlying mechanisms and to understand the effective levels of both forms of silver to be used in sustaining agricultural productions.

The present study investigates the impact of different Cr(VI) (50-200 mu M) treatments on Cucumis sativus L. seedlings which is worldwide grown in river catchments. Chromium (VI) treatments showed significant (P < .05) reduction in growth, photosynthetic pigments, total protein content and PSII performance, which was in concurrence with a significant (P < .05) increase in the accumulation of Cr(VI) (up to 587 +/- 18.19 mu g Cr g(-1) in roots), lipid peroxidation (MDA: up to 483%), H2O2 (up to 453%) and O-2(-) (up to 551%) compared to the control seedlings. Chlorophyll fluorescence parameters, such as F-m, F-v, F-v/F-m, F-m/F-0 and F-v/F-0, were declined while F-0 showed enhancements (P < .05). Energy flux parameters, such as Phi_E-0, Psi_0, PIABS, declined; however, ABC/RC, ET0/RC, DI0/RC and TR0/RC increased significantly (P < .05) under Cr(VI) treatments as compared to control. In addition, the levels of qP were reduced while NPQ was appreciably enhanced under different Cr(VI) treatments. The histochemical observations of H2O2 and O-2(-) were in accordance with their total estimation. Furthermore, Cr(VI) also severely injured the anatomical structure of roots. This study suggests that a higher accumulation of Cr(VI) in cucumber seedlings warrants serious attention in the studied catchments of the Ganges river to avoid any food contamination and biomagnifications to higher trophic levels.

Due to the adverse impacts of climate change on earth systems the research in this field has been profoundly taken a part in all scientific arenas since last few decades. The deleterious impacts of climate change on agricultural production are challenging the food security of the world in terms of quantity and quality both. Wheat, rice, maize, vegetables, fruits and fish-food provide food security for more than half of the world and are under immense pressure of changing climate. This review is an overview of the significant impacts associated with climate change on these food sources. In present synthesis, various phenological, physiological, biochemical and reproductive responses in major food crops have been summarized emphasizing the vulnerable growth and development stages. Winter and summer sensitivity responses, and morpho-biochemical acclimation patterns have also been summarized. Sustenance in wheat and rice production is evident but impacts of increasing temperatures are negating this on bio-physiological level impacts. Maize crops are experiencing more impacts on yield as compared to wheat and rice. Fruits and vegetable production is highly vulnerable to climate change at their reproductive stages and also due to more disease prevalence. Fisheries as a critical animal food source; is in extreme danger as apparent changes in their habitat and unmanageable environmental conditions are producing extreme losses. This review also provides an account of stress responses and useful adaptive measures. This synthesis may be helpful in understanding manifold dimensions and interactions of climate change impacts on selected major food sources of the world. (C) 2015 Elsevier B.V. All rights reserved.

Wetlands are very unique ecosystem with high productivity and several ecosystem services. The high altitude wetlands play very unique and important role in the glaciated river basins. They serve as storage during rainy period and release water during throughout the dry season. The wetlands in the high altitudes are under stress due to changes in basic natural feeding systems which are glaciers and precipitation. The increase in temperature in recent decades has exaggerated the problem. The present paper reviews the importance and status of high altitude wetlands and assesses the issues to be addressed.