Distribution and sources of organic contaminants in surface sediments of Hooghly river estuary and Sundarban mangrove, eastern coast of India.

This study investigated polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds such as polychlorinated biphenyls (PCBs) and DDT-related pesticides in surface sediments of Hooghly estuary and the Sundarban mangrove wetlands. Concentrations of ∑17PAH, ∑182PCB and ∑6DDT ranged from 15.4 to 1731, not detected (nd) to 13.5 and nd to 8.97 ng g-1 dry weight, respectively. Low levels of PCBs and low to moderate concentrations of DDTs and PAHs reflected recent development in West Bengal, which was dominated by agriculture and multifarious industries in the past. Diagnostic ratios suggested that major sources of PAHs are combustion processes, DDTs are input by agriculture, antifouling paints and public health campaigns, and organochlorines are predominantly from industrial origin. Heavier PCB congeners suggest local sources and short-range transport of such chemicals. Decision makers may use these findings for managing the Hooghly River watershed in order to promote a sustainable development on the eastern coast of India.

Monitoring of genotoxicity in marine zooplankton induced by toxic metals in Ennore estuary, Southeast coast of India.

The present study provides preliminary in-situ data on genetic integrity of marine zooplankton. Paracalanus parvus, Oithona rigida and Euterpina acutifrons were collected during four different seasons (summer, pre-monsoon, monsoon and post-monsoon) from 2011 to 2012 in Ennore and Kovalum estuaries. DNA damage levels in different zooplankton were analyzed by comet assay and were correlated with different environmental stressors. Spatial and temporal variations in DNA damage was observed in all the species. Zooplankton from Ennore estuary showed significantly lower genetic integrity. Particulate, sediment, and zooplankton fractions of Pb, Ni, Cu, Cr and Co were associated with high DNA damage during the period of lowest pH, salinity and dissolved oxygen. Zn and Cd showed lower genotoxic impact than the other metals. Feeding modes strongly influenced the genetic integrity in the zooplankton species studied. These results support the use of comet assay as a tool in effectively monitoring genotoxicity in marine plankton communities.

An integrated use of multiple biomarkers to investigate the individual and combined effect of copper and cadmium on the marine green mussel (Perna viridis).

The present study documents individual and combined sub-lethal effect of one redox active (copper) and one non-redox active (cadmium) metal on green mussel (Perna viridis). The mussels were exposed to 60 µg L(-1) of Cu and 150 µg L(-1) of Cd (individually and in combination) for 21 days. Histopathological and ultrastructural studies revealed significant metal induced alterations such as vacuolization, fusion of gill lamellae, enhance mucous deposition, hyperplasia and necrosis in gills. Antioxidant enzyme assays revealed significant increase in superoxide dismutase (SOD), glutathione S-transferase (GST) and glutathione peroxidase (GPx) activity. Similarly, single exposure to Cd and Cu caused significant induction in Malate dehydrogenase (MDH) activity. However, combined Cu+Cd exposure modulated suppression in MDH activity. Unlike MDH, Cu and Cd individual exposure resulted in a decrease in esterase (EST) activity, but their combined exposure caused an induction. Non-enzymatic biomarkers such as lipid peroxidation (LPO) and metallothionein (MT) levels showed no significant change in response to Cu exposure, whereas, individual Cd exposure or Cd exposure in combination with Cu caused significant changes in their levels. Comet assay revealed a significant increase in DNA damage upon metal exposure. These results indicate that Cu (redox active) and Cd (non-redox active) can induce measurable physiological, biochemical as well as genotoxic perturbations in mussels even at sub-lethal concentrations. A monitoring programme based on the biomarkers discussed here would be useful to study the effect of metal pollutants reaching the coastal waters.

Seasonal variations in species composition, abundance, biomass and production rate of tintinnids (Ciliata: Protozoa) along the Hooghly (Ganges) River Estuary, India: a multivariate approach.

The study is the first documentation of seasonal variations in species composition, abundance and diversity of tintinnid (Ciliata: Protozoa), in relation to water quality parameters along the stretch of the Hooghly (Ganges) River Estuary (HRE), eastern coastal part of India. A total of 26 species (22 agglomerated and 4 non-agglomerated) belonging to 8 genera has been identified from 8 study sites where Tintinnopsis (17 species) represented the most dominant genera, contributing up to 65 % of total tintinnid community followed by Tintinnidium (2 species), Leprotintinnus (2 species) and Dadayiella, Favella, Metacylis, Eutintinnus and Helicostomella (each with solitary species). The maximum (1,666 ind. l(-1)) and minimum (62 ind. l(-1)) abundance of tintinnids was recorded during post-monsoon and monsoon, respectively. A distinct seasonal dynamics in terms of biomass (0.005-2.465 µg C l(-1)) and daily production rate (0.04-3.13 µg C l(-1) day(-1)) was also noticed, accounting highest value during pre-monsoon. Chlorophyll a and nitrate were found to be potential causative factors for the seasonal variations of tintinnids as revealed by a stepwise multiple regression model. The result of ANOVA showed a significant variation between species abundance and months (F = 2.36, P ≤ 0.05). k-dominance curves were plotted to determine the comparison of tintinnid dominance between the investigated stations. Based on a principal component analysis (PCA), three main groups were delineated with tintinnid ciliates and environmental parameters. The changes in lorica morphology in terms of temperature and salinity, recorded for three dominant species, provided information on the ecological characteristics of the species assemblage in this estuarine system.

Perfluorinated compounds in surficial sediments of the Ganges River and adjacent Sundarban mangrove wetland, India.

This study reports the first evidence of the quantification of two dominant perfluorinated compounds (PFCs), namely perfluorooctanesulfate (PFOS) and perfluorooctannoate (PFOA), in surface sediment samples (0-5 cm; n=13) from the Ganges (Hugli) River including Sundarban wetland, India using HPLC-MS/MS. The concentrations of PFOA exhibited a wide range of concentrations from <0.5 to 14.09 ng/g dry wt, whereas the concentration of PFOS was always below the detection limit of <0.5 ng/g dry wt. A consistent enrichment of PFOA was recorded in all the five sites of Sundarban (mean value 11.61±1.86) whereas it was of moderate concentration or below the detection level in the seven sites along with the lower stretch of the Ganges (Hugli) River estuary (mean value 5.96 ng/g dry wt±5.36). Wastewater and untreated effluents are likely the major causes of accumulation of PFCs in sediments. The present paper could be used as baseline study to assess future monitoring programs of the ecosystem.

Biogeochemistry of mercury and methylmercury in sediment cores from Sundarban mangrove wetland, India--a UNESCO World Heritage Site.

This study was performed to elucidate the distribution, concentration trend and possible sources of total mercury (Hg(T)) and methylmercury (MeHg) in sediment cores (<63 µm particle size; n = 75) of Sundarban mangrove wetland, northeastern part of the Bay of Bengal, India. Total mercury was determined by atomic absorption spectrometry (AAS) in a Leco AMA 254 instrument and MeHg by gas chromatography-atomic fluorescence spectrometry (GC-AFS). A wide range of variation in Hg(T) (0.032-0.196 µg g(-1) dry wt.) as well as MeHg (0.04-0.13 ng g(-1) dry wt.) concentrations revealed a slight local contamination. The prevalent low Hg(T) levels in sediments could be explained by sediment transport by the tidal Hugli (Ganges) River that would dilute the Hg(T) values via sediment mixing processes. A broader variation of MeHg proportions (%) were also observed in samples suggesting that other environmental variables such as organic carbon and microbial activity may play a major role in the methylation process. An overall elevated concentration of Hg(T) in surface layers (0-4 cm) of the core is due to remobilization of mercury from deeper sediments. Based on the index of geoaccumulation (I (geo)) and low effects-range (ER-L) values, it is considered that the sediment is less polluted by Hg(T) and there is less ecotoxicological risk. The paper provides the first information of MeHg in sediments from this wetland environment and the authors strongly recommend further examination of Hg(T) fluxes for the development of a detailed coastal MeHg model. This could provide more refine estimates of a total flux into the water column.