Sub-lethal effects of deltamethrin and permethrin resulted in ultrastructural alterations in scales and oxygen uptake changes of Anabas testudineus (Bloch, 1792).

The present study used scanning electron microscopy (SEM) to assess the toxicity of sub-lethal concentrations of deltamethrin (0.035, 0.007 and 0.0007 mg L-1) and permethrin (0.93, 0.093 and 0.0093 mg L-1) on the ultrastructure of the scales of Anabas testudineus (Bloch, 1792) during a 21 day exposure. The oxygen uptake of the fish during deltamethrin (0.007 and 0.0007 mg L-1) and permethrin (0.093 and 0.0093 mg L-1) exposure was also investigated. The SEM studies revealed abnormal morphological alterations and modifications of fish scales, which were concentration-dependent. Deltamethrin-exposed fish showed severe deformation and fusion of two circuli in different rows, thereby disrupting the normal radii pattern. This fusion was probably caused by the cyanide moiety of the pesticide. On the other hand, permethrin characteristically produced a thick mucus layer over the scale surface. The different concentrations of both the pesticides affected circuli pattern with severe breakage of circuli and loss of lepidonts present over their ridges. Erythrocyte extrusions were also seen at several places over the scale surface. There was significant reduction of oxygen uptake in fish exposed to permethrin at both the concentrations, but in deltamethrin treatments significant reduction occurred only at the higher concentration of 0.007 mg L-1, though this was less than the lower permethrin concentration of 0.0093 mg L-1, and moreover effects of both the pyrethroids on oxygen consumption increased at higher concentrations.

Short-term insecticide exposure amid co-occurring stressors reduces diversity and densities in north-east Indian experimental aquatic invertebrate communities.

Globally, river pesticide concentrations are associated with regional and local stream invertebrate diversity declines. Pesticides often co-occur with elevated nutrients (e.g. nitrogen and phosphorus) and sediments related to agriculture, making their individual effects difficult to disentangle. These effects are also less well studied in Asia, than in other geographic regions. Within Asia, India is one of the largest producers and users of pesticides and has approximately 60% of total land mass used for agriculture. Here we examine the responses of Indian river invertebrate communities subjected to malathion, nutrients, and sediment additions in a semi-orthogonal design, in three sequential (through time) short-term (120 h) mesocosm experiments. Additionally, a series of single-species toxicity tests were run that used 24 h exposure and 72 h recovery to examine the sensitivity of 13 local invertebrate taxa to malathion, and 9 taxa to cypermethrin, comparing these results to those from other biogeographic regions. Mesocosm results indicate that malathion exposure had a major effect compared to other stressors on communities, with a lesser effect of nutrients and/or sediments. In mesocosms, taxa richness, total abundance and the abundance of sensitive species all declined associated with malathion concentrations. Comparisons of organism sensitivities from other geographic locations and those in the current paper suggest taxa in India are relatively tolerant to malathion and cypermethrin. Our results further reinforce that the high observed aquatic pesticide concentrations known to occur in Asian freshwater ecosystems are likely to be negatively affecting biodiversity, homogenising biota towards those most stress tolerant.

Cu and Pb accumulation and removal from aqueous medium by Enydra fluctuans Lour. (Asteraceae) - a medicinal plant with potential for phytoremediation.

Enydra fluctuans Lour. (Asteraceae) is an edible semi-aquatic floating or trailing herbaceous plant widely distributed in tropical Africa, South and South East Asia, and Australia. Its leaves, which are consumed as a vegetable, are also used in traditional medicine to treat several diseases. The efficacy of this plant in removal of copper and lead from aqueous medium was tested in the present study. The plants were exposed to graded measured concentrations of 0.55-10.2 mg Cu L-1 and 11.5-50.2 mg Pb L-1 in hydroponic systems. Controls without added Cu and Pb were maintained under identical conditions. Cu and Pb were estimated by atomic absorption spectrometry, and the bioconcentration factor (BCF) and the translocation factor (TF) were calculated for each element at the different concentrations. Accumulation of both Cu and Pb was significantly higher in root than that in leaf and stem. Though all the bioconcentration factor (BCF) values were greater than unity, none of the translocation factor (TF) values was greater than unity, indicating that this plant could not be considered a hyperaccumulator of these metals. Nevertheless, E. fluctuans could remove Cu from aqueous medium at rates ranging from 98.8 to 99.7%, with a mean reduction of 99.2% after 96-h exposure at various concentrations. The removal of Pb ranged from 97.1 to 99.1%, with a mean reduction of 98.2%. Thus, E. fluctuans showed high potential for removal of Cu and Pb from aqueous medium and has the prospect of being used in phytoremediation of these metals.

Acute toxicity of lead in fresh water bivalves Lamellidens jenkinsianus obesa and Parreysia (Parreysia) corrugata with evaluation of sublethal effects on acetylcholinesterase and catalase activity, lipid peroxidation, and behavior.

The median lethal concentrations (LC50) of Pb at 96 h were 8.84, 192.14, and 3.22 mg L-1 for pre-reproductive and reproductive individuals of Lamellidens jenkinsianus obesa and reproductive individuals of Parreysia (Parreysia) corrugata, respectively. Thus, young L. j. obesa were much more sensitive to Pb than its adults, while P. (P.) corrugata was the most sensitive. However, all the three values were much higher than the Pb levels commonly found in natural waters, and indicative of the tolerance of these mollusks to acute, short-term Pb exposure. In contrary to these findings, acetylcholinesterase (AChE) and catalase (CAT) activities were affected and lipid peroxidation (LPO) elevated in young L. j. obesa and P. (P.) corrugata in 21-day sublethal toxicity tests at 26-68 ppb Pb concentrations, which might be considered environmentally realistic. Some behavioral patterns such as number of movement (Mov) and durations of foot mobilization together with siphon extensions (FSE) were reduced, and the durations of valves remaining completely closed without any extension of foot and siphons (VC) increased significantly at 25-69 ppb Pb as well. Thus, the study revealed significant interspecific differences as well as that between life stages of the same species, suggesting that apparently hardy species could be impacted by low Pb concentrations in their young stages. Further, a multi-biomarker approach involving biological effects, anti-oxidative enzyme activity and easy-to-measure behavioral elements could comprise a valuable tool in assessment of Pb-induced stress in freshwater bivalves.

Arsenic-Iron Relationships in Aquifers of North East India: Implications for Public Health and the Environment.

Arsenic (As) contamination of groundwater in the Ganga-Brahmaputra-Meghna basin of India and Bangladesh poses severe risk to human health and the environment. Arsenic in the groundwater of this area is largely geogenic, derived from the microbial reductive dissolution of iron (Fe) oxyhydroxide and subsequent release of the sorbed As. The present study examined the correlation between As and Fe in groundwater sources in four districts of Manipur state, and in Cachar, Hailakandi, and Karimganj districts in the Barak Valley region of south Assam. Both the study areas are located in the northeastern region of India. The results reveal that As-Fe correlations in Manipur were more significant and positive, when compared to those in Barak Valley. The significance of these findings in the mobilization and transport of arsenic in the fluvial environment of these two areas of North East India, and in the prediction of arsenic-safe aquifers, are discussed and compared with existing literature. These findings, therefore, have implications in the sustainable management of groundwater resources in the study areas.

Acute toxicity of cadmium in Anisops sardeus (Heteroptera:Notonectidae): Effects on adult and nymphal survival and swimming behavior.

Adult female and male, and final instar nymph of Anisops sardeus (Heteroptera: Notonectidae) were exposed to graded concentrations of cadmium in 96h static-with-renewal acute toxicity tests, which were conducted in dry (March) and wet (May-June) seasons. The 96h LC50 values for instar V nymph, adult female and male were found to be 0.9, 0.59 and 0.51mgL-1 Cd, respectively, in wet season, while these were 26.7 and 20.2mgL-1 Cd for adult female and male, respectively, in dry season. Adult males were most sensitive to Cd, followed by females in both seasons, while highest tolerance in wet season was observed in instar V nymph. There was a steep decline in LC50 values from 24 to 96h in wet season. Besides mortality at higher concentrations of Cd, sublethal effects in terms of reduced 'velocity magnitude' (swimming speed) and mostly increased 'rotation angle' (turning angle) could be discerned at concentrations as low as 0.03mgL-1. The swimming pattern of Cd-exposed nymph and adults were also affected. Based on the bioaccumulation factor (BAF) values, A. sardeus could be designated as a macroconcentrator of Cd (BAF > 2), with highest Cd accumulation in instar V nymph, followed by that in female, and with lowest Cd accumulation in male.

Phytoremediation of lead using Ipomoea aquatica Forsk. in hydroponic solution.

Ipomoea aquatica Forsk., an aquatic macrophyte, was assessed for its ability to accumulate lead (Pb) by exposing it to graded concentrations of this metal. Accumulation of Pb was the highest in root followed by that in stem and leaf with translocation factor (TF) values of less than unity. On the other hand, all bioconcentration factor (BCF) values in root, stem and leaf were greater than unity. Furthermore, exposure to Pb concentrations over about 20 mg L(-1) induced colour changes in the basal portion of stem which had significantly higher Pb accumulation than that in the unaffected apical part. This resulted in sequestration of excess metal in affected stem tissue, which could take up Pb by the process of caulofiltration or shoot filtration, and served as a secondary reservoir of Pb in addition to the root. The apical parts contained less lead and could regrow roots from nodes and survive when kept in Pb-free medium. The ability of the plant to store Pb in its root and lower part of stem coupled with its ability to propagate by fragmentation through production of adventitious roots and lateral branches from nodes raises the possibility of utilizing Ipomoea aquatica for Pb phytoremediation from liquid effluent.

Sublethal toxicity of commercial formulations of deltamethrin and permethrin on selected biochemical constituents and enzyme activities in liver and muscle tissues of Anabas testudineus.

The freshwater fish Anabas testudineus was exposed for 21 days to two commercial formulations of synthetic pyrethroids deltamethrin and permethrin at sublethal concentrations of 0.007 and 0.0007 mg L(-1), and 0.093 and 0.0093 mg L(-1), that represented 10% and 1%, respectively, of the 96 h LC50 of these two pesticides for this fish. The glycogen, protein and lactic acid contents, along with succinate dehydrogenase (SDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) enzyme activities in liver and muscle tissues of control and pesticide-exposed fish were estimated. When compared with those of control fish, significant depletion of glycogen content was observed in liver, and that of protein in muscle tissue of fish treated with both the pesticides at their higher as well as lower concentrations. Lactic acid reduction was significant only in fish muscle treated with deltamethrin. SDH level was reduced significantly in both liver and muscle tissues except in fish exposed to 0.0093 mg L(-1) permethrin. AST level was reduced significantly in liver and muscle tissues and ALT in muscle tissue of deltamethrin treated fish only. It is concluded that deltamethrin, a type-II pyrethroid, is more toxic to fish than the type-I pyrethroid permethrin and is capable of rendering toxicity at a dose as low as 1% of its LC50 value.

Biomarkers of type II synthetic pyrethroid pesticides in freshwater fish.

Type II synthetic pyrethroids contain an alpha-cyano group which renders them more neurotoxic than their noncyano type I counterparts. A wide array of biomarkers have been employed to delineate the toxic responses of freshwater fish to various type II synthetic pyrethroids. These include hematological, enzymatic, cytological, genetic, omic and other types of biomarkers. This review puts together the applications of different biomarkers in freshwater fish species in response to the toxicity of the major type II pyrethroid pesticides and assesses their present status, while speculating on the possible future directions.

Toxicity of endosulfan to tadpoles of Fejervarya spp. (Anura: Dicroglossidae): mortality and morphological deformities.

The acute toxicity of endosulfan to the tadpoles of three coexisting species of the anuran genus Fejervarya revealed 96 h LC50 values of 46.715, 6.596, and 3.015 µg l(-1) for Fejervarya sp.1, F. teraiensis and Fejervarya sp.2, respectively. Toxicity of endosulfan was also tested at the sublethal concentrations of 5 and 0.5, and 0.3 and 0.03 µg l(-1) (c 10 and 1% of their respective 96 h LC50 values) in Fejervarya sp.1 and Fejervarya sp.2, and 0.35 and 0.18 µg l(-1) (c 5 and 2.5% of 96 h LC50) in F. teraiensis. Endosulfan was observed to cause mortality at concentrations as low as c 1, 2.5 and 10% of their respective 96 h LC50 values in Fejervarya sp.2, F. teraiensis, and Fejervarya sp.1. Such vulnerabilities are likely to have implications for the survival of natural populations of these co-existing species as well as other anurans present in the study area where pesticide use is relatively high in the tea plantations. Morphological deformities caused by endosulfan comprised failure to develop one or both forelimb in Fejervarya sp.1 and F. teraiensis, stunted hindlimb growth in Fejervarya sp.1, and axial malformation in Fejervarya sp.1 and Fejervarya sp.2. Fore- and hind-limb deformities were likely to have occurred due to the impairment of thyroid metabolism by endosulfan. These effects illustrate the threat that continued endosulfan use poses to natural populations of anuran amphibians.

Groundwater quality in Imphal West district, Manipur, India, with multivariate statistical analysis of data.

The aim of this paper was to analyze the groundwater quality of Imphal West district, Manipur, India, and assess its suitability for drinking, domestic, and agricultural use. Eighteen physico-chemical variables were analyzed in groundwater from 30 different hand-operated tube wells in urban, suburban, and rural areas in two seasons. The data were subjected to uni-, bi-, and multivariate statistical analysis, the latter comprising cluster analysis (CA), principal component analysis (PCA), and factor analysis (FA). Arsenic concentrations exceed the Indian standard in 23.3% and the WHO limit in 73.3% of the groundwater sources with only 26.7% in the acceptable range. Several variables like iron, chloride, sodium, sulfate, total dissolved solids, and turbidity are also beyond their desirable limits for drinking water in a number of sites. Sodium concentrations and sodium absorption ratio (SAR) are both high to render the water from the majority of the sources unsuitable for agricultural use. Multivariate statistical techniques, especially varimax rotation of PCA data helped to bring to focus the hidden yet important variables and understand their roles in influencing groundwater quality. Widespread arsenic contamination and high sodium concentration of groundwater pose formidable constraints towards its exploitation for drinking and other domestic and agricultural use in the study area, although urban anthropogenic impacts are not yet pronounced.

Effects of cadmium chloride on oxygen consumption and gill morphology of Indian flying barb, Esomus danricus.

Effects of three sub lethal concentrations of cadmium chloride (0.636, 0.063 and 0.006 mg l(-1)) on oxygen consumption and gill morphology in Indian flying barb, Esomus danricus (Hamilton-Buchanan), a teleost fish, were studied. When compared to control, 0.636 mg l(-1) of cadmium chloride after 7,14, 21 and 28 day exposure showed a significant decline in rates of oxygen consumption at 32.98, 28.40, 23.88 and 21.69 ml hr(1) 100 g(-1) of tissue, respectively; while, 0.063 mg l(-1) of cadmium chloride for the same exposure durations showed a significant decline in rates of oxygen consumption at 34.28, 29.30, 28.05 and 26.47 ml hr(1)100 g(-1) of tissue, respectively. However, significant decline in the rate of oxygen consumption at 0.006 mg l(-1) of cadmium chloride could be observed from 21st day of exposure. Gill tissue showed various histopathological changes including epithelial lifting, hyperplasia, mucous secretion, marked leucocyte infiltration in the epithelium after 28 days of cadmium chloride exposure.

Euglenoid blooms in the floodplain wetlands of Barak Valley, Assam, North eastern India.

Red blooms of Euglena sp. in the floodplain wetland ecosystems of Barak Valley, Assam, India, were found to be induced by high concentrations of NH3-N, NO3, Fe, Mg and to some extent, PO4, Cu and Zn in their water. The trace elements were rapidly accumulated by the bloom organisms to high levels, whereby their concentrations in the water declined, leading to a collapse of the bloom, which tended to reappear as decomposition again led to the release of the nutrients. The bloom also harboured fairly high density of certain other algae and zooplankton, thereby acting as a sub-system within the wetland ecosystem. The bloom is non-toxic and is exploited as a fish food by the fish-farmers who artificially induce a bloom for augmenting the growth of surface-feeding species of fishes.