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The study first investigated the spatial distribution, diversity, and biomass of the planktonic choreotrich ciliate tintinnids inhabiting the biosphere reserve, the core region of Indian Sundarban mangrove wetland. A total of 21 species (eight genera and six families) were recorded including agglomerated and non-agglomerated or hyaline forms from these intricate estuarine network systems. Maximum mean abundance (2747 ± 111 individuals L−1) and species diversity ( H′ = 2.32) of tintinnid ciliate were recorded at the sampling site located towards the Bay of Bengal whereas lower abundance (666 ± 56 individuals L−1) and diversity ( H′ = 1.55) were encountered towards inner part of the estuary. Tintinnopsis represented the most dominant agglutinated genus comprising of Tintinnopsis beroidea, Tintinnopsis fimbriata, Tintinnopsis cylindrica, Tintinnopsis tocantinensis, and Tintinnopsis radix, accounting ∼52% of total tintinnid community. The agglomerated forms Amphorellopsis tetragona, Eutintinnus apertus, Codonellopsis lusitanica, and T. fimbriata were recorded for the first time in this region. The biomass value exhibited wide range of variations (0.03 ± 0.09 to 12.4 ± 1.1 μg C L−1), accounting maximum value towards seaward region. The small-sized tintinnid (lorica length <40 μm) contributed the most dominant group (sharing ∼85% of total species abundance) in this core region and their presence was mainly governed by factors, namely, chlorophyll α, salinity, and nutrients (nitrate and silicate). The results of combining multivariate methods (RELATE and BIOENV analyses) reveal that chl a and nitrate were the potential significant factors for tintinnid abundance and distribution. [ABSTRACT FROM AUTHOR]

A multispecies bloom caused by the centric diatoms, viz. Coscinodiscus radiatus, Chaetoceros lorenzianus and the pennate diatom Thalassiothrix frauenfeldii was investigated in the context of its impact on phytoplankton and microzooplankton (the loricate ciliate tintinnids) in the coastal regions of Sagar Island, the western part of Sundarban mangrove wetland, India. Both number (15-18 species) and cell densities (12.3×103cellsl−1 to 11.4×105cellsl−1) of phytoplankton species increased during peak bloom phase, exhibiting moderately high species diversity (H′=2.86), richness (R′=6.38) and evenness (E′=0.80). The diatom bloom, which existed for a week, had a negative impact on the tintinnid community in terms of drastic changes in species diversity index (1.09-0.004) and population density (582.5×103 to 50×103indm−3). The bloom is suggested to have been driven by the aquaculture activities and river effluents resulting high nutrient concentrations in this region. An attempt has been made to correlate the satellite remote sensing-derived information to the bloom conditions. MODIS-Aqua derived chlorophyll maps have been interpreted. [ABSTRACT FROM AUTHOR]

The present work is the first attempt to compare the data of a comprehensive study of the origin and distribution of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in surface sediments (<63 μm) from 18 sampling stations, 9 from Sundarban of Bangladesh and 9 from Indian counterpart. Σ19PAHs concentration in sediments showed wide variations from 208.3 to 12,993.1 ng g dry weight in Indian Sundarban, whereas 208.4 to 4,687.9 ng g in the case of Bangladesh. Fluoranthene, pyrene, benzo(b)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were predominant species for both the countries. The PAH diagnostic ratios indicated that the PAHs in sediments from both the countries were of mixed source of hydrocarbons of both petrogenic and pyrolytic origin. According to the numerical effect-based sediment quality guidelines, the levels of PAHs in the Sundarban wetland of Bangladesh and India should not exert adverse biological effects. The TEQ values calculated for samples from the Bangladesh and Indian Sundarban varied from 13.68 to 1,014.75 and 1.31 to 2,451 ng g d.w. with an average of 221.02 and 358.63 ng g, respectively. The overall contamination status of PAH was higher in India than Bangladesh. [ABSTRACT FROM AUTHOR]

The distribution and potential sources of 16 polycyclic aromatic hydrocarbons (PAHs) in sediment cores (<63 μm particle size) of the Sundarban mangrove wetland, northeastern coast of Bay of Bengal (India), were investigated by gas chromatography coupled to mass spectrometry. The total concentrations of 16 PAHs (∑16PAHs) ranged from 132 to 2938 ng/g, with a mean of 634 ng/g, and the sum of 10 out of 16 priority PAHs (∑10PAH) varied from 123 to 2441 ng/g, with a mean of 555 ng/g, and the 5 carcinogenic PAHs (benzo[ b]fluoranthene, benzo[ k]fluoranthene, benzo[ a]pyrene, indeno[1,2,3- cd]pyrene, and dibenz[ a,h]anthracene) accounted for 68–73% of the priority PAHs. Maximum concentrations of the sediment core were obtained at subsoil depth of 12–16 cm. The prevalence of four to six aromatic ring PAHs and cross-plots of specific isomer ratios such as phenanthrene/anthracene, fluoranthene/pyrene, and methylphenanthrenes/phenanthrene suggested the predominance of wood and coal combustion sources, the atmospheric deposition, and surface runoff to be the major transport pathways. A good correlation existed between the benzo[ a]pyrene level and the total PAH concentrations, making this compound a potential molecular marker for PAH pollution. Total TEQ values calculated for samples varied from 6.95 ng/g TEQ to 119 ng/g TEQ, with an average of 59 ng/g dry weight TEQ. The baseline data can be used for regular monitoring, considering the industrial and agricultural growth around this coastal environment. [ABSTRACT FROM AUTHOR]

The paper presents the first comprehensive account of congener profiles of polycyclic aromatic hydrocarbons (PAHs) in intertidal bivalve mollusks [ Meretrix meretrix, Macoma birmanica, and Sanguilonaria (Soletellina) acuminata] of Sunderban mangrove wetland (India). The main aim of this work was to use the bivalves as bioindicators of the contamination of the 16 USEPA PAH. The PAH profile in bivalves is largely dominated by a petrogenic fingerprint, with over-imposition of pyrolytic PAH sources, as evidenced by diagnostic molecular ratios. Bioaccumulation factors (BAF) of individual compounds from the sediments were calculated, and it reveals overall higher values in the visceral mass of the bivalves. S acuminata showed significantly higher levels of PAHs, especially the high molecular weight (HMW) PAHs, compared to the other two species as a sensitive indicator of trace organic stress in future monitoring programs. [ABSTRACT FROM AUTHOR]

The paper presents the first comprehensive survey of congener profiles of polychlorinated biphenyls (PCBs) in core sediment samples (<63 μm particle size) covering seven sites in Sunderban mangrove Wetland, north-eastern part of the Bay of Bengal. Results pointed out a non-homogenous contamination of the wetland with Σ23PCB values ranging from 0.5 to 26.9 ng g-1 dry weight, reflecting very low to moderate contamination closely in conformity to other Asian coastal environment. The general decreasing order of the dominant congeners to the total load was: CB138 > 153 > 149 > 101, indicating the predominance of hexa-chlorinated congeners. The spatial distribution revealed significant differences in concentration related to local urbanization with industrial and land-based sources. No uniform temporal trend on PCB levels was recorded probably due to particular hydrological characteristics of the wetland and/or non-homogenous inputs from point sources. Strong positive correlations between the seven dominant congeners suggest their common sources and similar environmental behaviors. These results were also used for a risk assessment evaluation in the Sunderban wetland, showing that the present PCB levels were exceeding in few cases the lower limit of sediment quality guidelines of Environmental Protection Agency and Canadian Council of Ministers of the Environment. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive account regarding concentration, distribution and possible sources of trace elements (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in 20–30 cm sediment cores (<63 μm particle size) collected at the confluence of the Ganges River and Bay of Bengal (Sunderban wetland, India). This work aims to evaluate the fluvio-marine and geochemical processes influencing the metal distribution. The most interesting features are the downward increase of concentrations of majority of the elements reaching overall maximum values at a depth of 10–15 cm observed in station Lot No.8 located along the main stream of the Ganges estuary as well as an overall elevated concentration of all the elements in the lower littoral zone. The interelemental relationship revealed the identical behaviour of elements during its transport in the estuarine environment. The overall variation in concentration can be attributed to differential discharge of effluents originating from industrial and agricultural as well as from domestic sewage. Arsenic exceeded effects range – low (ER – L) concentrations, implying occasional or frequent adverse biological effects. For Cu, Ni and Cr a smaller proportion of samples had exceeded the ER – L values indicating that the dataset would be suitable for future use in evaluating predictive abilities of SQGs. [ABSTRACT FROM AUTHOR]

This paper presents the first comprehensive report of the organochlorine pesticide residues (OCs) such as hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane and its six metabolites (DDTs), and hexachlorobenzene (HCB) in core sediments (<63-μm particle size) from the Indian Sunderban wetland. The pooled mean values of the mass fraction of ΣHCHs, HCB, and ΣDDTs in the sediments were 0.05–12, 0.05–1.4, and 0.05–11.5 ng g−1 dry weight, respectively. The vertical distribution of pesticides reveals an erratic pattern. The concentration of four isomers of HCHs reveals a heterogenic distribution where γ-HCH (lindane) and β-HCH shared the dominant part. The mass fraction of HCB did not show any sharp spatial variation. The prevailing sequence of DDT metabolites indicates an active degradation of the parent compound in the sediments and/or inputs of already degraded pp’DDT to the region. Peak concentrations of HCH isomers and DDT metabolites have the potential to induce ecotoxicological impact as per the sediment quality guidelines. [ABSTRACT FROM AUTHOR]

The aim of this paper was to obtain the first screening ecotoxicological risk evaluation in the Sunderban wetlands, the largest prograding delta in the estuarine phase of the River Ganges. The characterization of exposure was conducted by means of an extensive survey of several persistent organic pollutants (PAHs, PCBs, DDTs, PBDEs, HCHs, HCB) measured in seven core sediments from the Sunderban wetlands, obtaining a dataset with more than 2200 analyses. The pollutant effects were assessed by the use of three different sediment quality guidelines (SQGs) previously developed in the literature to evaluate toxicity induced in sediment-dwelling organisms. The three different approaches chosen for risk assessment of the Sunderban were the consensus SQGs obtained by TEC (threshold effect concentration), PEC (probable effect concentration) and EEC (extreme effect concentration), the threshold/probable effect level (TEL/PEL) approach and, finally, the ERL-ERM guidelines, including the m-ERM-Q (mean ERM quotient). The evaluation of the toxicity induced by a mixture of the target pollutants indicated the importance of γ-HCH contamination in the Sunderban sediments despite the very low concentrations measured in core sediments. A different sensitivity for toxicity assessment due to quality guidelines was obtained, as the consensus SQGs based on TEC were less conservative and protective than the TEL and ERL approaches, while the use of m-ERM-Q seems to be the most powerful tool to predict the toxicity related to a contaminant mixture. [Copyright &y& Elsevier]