SEGH Articles

The Indian Sundarban Mangrove wetland: an ecological perspective

01 February 2012
Dr Sarkar has carried out research on the changes in the ecological and pollution status of the Indian Sundarban mangrove wetlands, as a result of intense anthropological pressures affecting the biotic and abiotic compartments of this fragile ecosystem.

 

Dr Santosh Sarkar is a professor at the Department of Marine Science, University of Calcutta in India. Over the past 30 years he has carried out research on the changes in the ecological and pollution status of the Sundarban mangrove wetland, as a result of intense anthropological pressures affecting the biotic and abiotic compartments of this fragile ecosystem. 

The Indian Sundarban is located in North East India, in close proximity to Kolkatta. It is the largest delta in the estuarine phase of the river Ganges, and is situated in the low-lying, meso-macrotidal, humid and tropical belt at the estuarine phase of the Ganges River and Bay of Bengal. The Sundarban hosts the world's largest mangrove forest together with associated flora and fauna.

There have been remarkable ecological changes due to multiple human activities. such as; excavation of sand from the sand dunes, dredging and intensive boating, deforestation, collection of prawn seed, immersion of idols in the river etc., thus affecting sediment and water quality as well as biodiversity.

Dr Sarkar has quantified the adverse impacts due to collection of tiger prawn seeds for aquacultural farms and molluscan shells for poultry feed and edible lime. Indiscriminate exploitation of these resources leads to a heavy reduction of the species concerned and other associated marine communities. The impacts of biodiversity loss and their after-effects on the ecobalance of the coastal system have become a matter of great concern to ecologists to maintain security and sustainability.

Collection of  tiger prawn seed (Penaeus monodon) from Sundarban coastal regions

Dr Sarkar first worked on the occurrence, distribution and sources of several persistent organic pollutants (POPs) (PAHs, PCBs, DDTs, PBDEs, HCHs, HCB) measured in  sediments from the Sundarban wetlands, obtaining a dataset with more than 2000 analyses. The POPs belong to a group of pollutants that are semivolatile, toxic and  bioaccumulative in nature and resist photolytic, chemical and biological degradation. The concentration of four isomers of  HCH exhibit a heterogenic distribution. Among the isomers and metabolites of HCH, DDT and PCB, alpha-HCH, pp ′-DDT and PCB 101, PCB 118,  PCB 153 and PCB 138  were found to be dominant. High ratios of metabolites of DDT to ∑ DDTs reveal recent use of DDT in this coastal environment. PBDE, an important group of brominated flame retardants (BFR), showed moderate to low contamination closely in uniformity to other Asian aquatic environments. The PAH diagnostic ratios indicated that the PAHs in sediment were of pyrolytic origin, contaminated by local vehicle combustion, biomass burning and domestic an industrial coal combustion.

Dr Sarkar performed the first screening ecotoxicological risk evaluation of the persistent organic pollutants (POPs) in the Sundarban wetland. 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 Sundarban were: (1) the consensus SQGs obtained by TEC (threshold effect concentration); (2) PEC (probable effect concentration; and (3) 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 gama-HCH contamination in the Sundarban sediments despite the very low concentrations measured in 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.

Collaborative research work with Michael Watts of the British Geological Survey, provided initial findings for arsenic speciation in four soft-bottom benthic polychaetes (Perenereis cultifera, Ganganereis sootai, Lumbrinereis notocirrata and Dendronereis arborifera) along with host sediments from the Sundarban mangrove wetland.  Arsenic concentrations in polychaete body tissues varied greatly, suggesting species-specific characteristics and inherent peculiarities in arsenic metabolism. Arsenic was generally present in polychaetes as arsenate (AsV) or arsenite (AsIII) (30 to 53 % as inorganic As) and dimethylarsinic acid (DMAV; <1 to 25 %). Arsenobetaine (AB; <16%), and PO4-arsenoriboside (8 to 48%) were also detected as minor constituents, whilst monomethylarsonic acid (MAV) was not detected in any of the polychaetes. The highest total As (14.7 mg kg-1 dry wt) was observed in the polychaete D. arborifera collected from the vicinity of a sewage outfall in which the majority of As was present as an uncharacterized compound (10.3 mg kg-1 dry wt) eluted prior to AB. Host sediments ranged from 2.5 to 10.4 mg kg-1 total As. This work supports the importance of speciation analysis of As, because of the ubiquitous occurrence of this metalloid in the environment, and its variable toxicity depending on chemical form. Follow up work is being carried out on further samples collected with the support of Royal Society funding.  This will enable consideration of a range of polychaete species in terms of diverse habitat and food preferences to assess the arsenic uptake pathways and to determine the influence of ecological factors on total As concentrations and species proportion in this wetland ecosystem.

Gradually a full picture of the growing impact of human activity on the pristine environment of the Sundarban mangrove wetlands is being developed.  This is gradually being achieved through multiple international collaborations and will provide vital information for the planning and use of land and waterways in the wetlands.

Professor Santosh Sarkar, Department of Marine Science, University of Kolkatta, Indiasarkar.santosh@gmail.com

References

Biogeochemistry of mercury and methylmercury in sediment cores from Sundarban mangrove wetland, India - a UNESCO World Heritage Site - Mousumi Chatterjee, João Canário, Santosh Kumar Sarkar, Vasco Branco, Nallamuthu Godhantaraman, Bhaskar Deb Bhattacharya, Asokkumar Bhattacharya  - Environmental Monitoring and Assessment, Springer. DOI:10.1007/s10661-011-2336-8 2011. http://www.springerlink.com/content/v16047jhk2027416/

Quantification and source identification of polycyclic aromatic hydrocarbons in core sediments from Sundarban Mangrove Wetland, India  - C. Domínguez; S. K. Sarkar, A Bhattacharya, M Chatterjee, B D Bhattacharya, E Jover,  J Albaigés, J M Bayona, Md. A Alam and K K Satpathy. Archives of Environmental Contamination and Toxicology, Springer Publishers, 59(1): 49 - 61, 2010.           http://www.springerlink.com/content/l32803q28210256t/

Metal concentrations in water and sediments from tourist beaches of   Acapulco, Mexico  - M.P. Jonathan, P.D. Roy, N. Thangadurai, S. Srinivasalu, P.F. Rodríguez Espinosa, S.K.Sarkar, C. Lakshumanan, M. Navarrete-López and N.P. Muñoz-Sevilla - Marine Pollution Bulletin, Springer, 62, 845-850, 2011. http://www.sciencedirect.com/science/article/pii/S0025326X11001135

Baseline of organotin contamination in sediments of Sunderban mangrove wetland and adjacent coastal regions, India - P . Anderson, S K Sarkar, B D Bhattacharya, M Chatterjee, K K Satpathy, T Peshkur and B Antizar-Ladislao. - Ecotoxicology,Springer, 20 (8), 1975-1983, 2011. DOI 10.1007/s10646-011-0739-5. http://www.springerlink.com/content/52j87u2658171821/

 

Keep up to date

SEGH Events

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Genotoxic effects of PM 10 and PM 2.5 bound metals: metal bioaccessibility, free radical generation, and role of iron 2018-10-09

    Abstract

    The present study was undertaken to examine the possible genotoxicity of ambient particulate matter (PM10 and PM2.5) in Pune city. In both size fractions of PM, Fe was found to be the dominant metal by concentration, contributing 22% and 30% to the total mass of metals in PM10 and PM2.5, respectively. The speciation of soluble Fe in PM10 and PM2.5 was investigated. The average fraction of Fe3+ and Fe2+ concentrations in PM2.5 was 80.6% and 19.3%, respectively, while in PM2.5 this fraction was 71.1% and 29.9%, respectively. The dominance of Fe(III) state in both PM fractions facilitates the generation of hydroxyl radicals (·OH), which can damage deoxyribose nucleic acid (DNA), as was evident from the gel electrophoresis study. The DNA damage by ·OH was supported through the in silico density functional theory (DFT) method. DFT results showed that C8 site of guanine (G)/adenine (A) and C6 site of thymine (T)/cytosine (C) would be energetically more favorable for the attack of hydroxyl radicals, when compared with the C4 and C5 sites. The non-standard Watson–Crick base pairing models of oxidative products of G, A, T and C yield lower-energy conformations than canonical dA:dT and dG:dC base pairing. This study may pave the way to understand the structural consequences of base-mediated oxidative lesions in DNA and its role in human diseases.

  • A systematic review on global pollution status of particulate matter-associated potential toxic elements and health perspectives in urban environment 2018-10-08

    Abstract

    Airborne particulate matter (PM) that is a heterogeneous mixture of particles with a variety of chemical components and physical features acts as a potential risk to human health. The ability to pose health risk depends upon the size, concentration and chemical composition of the suspended particles. Potential toxic elements (PTEs) associated with PM have multiple sources of origin, and each source has the ability to generate multiple particulate PTEs. In urban areas, automobile, industrial emissions, construction and demolition activities are the major anthropogenic sources of pollution. Fine particles associated with PTEs have the ability to penetrate deep into respiratory system resulting in an increasing range of adverse health effects, at ever-lower concentrations. In-depth investigation of PTEs content and mode of occurrence in PM is important from both environmental and pathological point of view. Considering this air pollution risk, several studies had addressed the issues related to these pollutants in road and street dust, indicating high pollution level than the air quality guidelines. Observed from the literature, particulate PTEs pollution can lead to respiratory symptoms, cardiovascular problems, lungs cancer, reduced lungs function, asthma and severe case mortality. Due to the important role of PM and associated PTEs, detailed knowledge of their impacts on human health is of key importance.

  • Interactions between polycyclic aromatic hydrocarbons and epoxide hydrolase 1 play roles in asthma 2018-10-06

    Abstract

    Asthma, as one of the most common chronic diseases in children and adults, is a consequence of complex gene–environment interactions. Polycyclic aromatic hydrocarbons (PAHs), as a group of widespread environmental organic pollutants, are involved in the development, triggering and pathologic changes of asthma. Various previous studies reported the critical roles of PAHs in immune changes, oxidative stress and environment–gene interactions of asthma. EPHX1 (the gene of epoxide hydrolase 1, an enzyme mediating human PAH metabolism) had a possible association with asthma by influencing PAH metabolism. This review summarized that (1) the roles of PAHs in asthma—work as risk factors; (2) the possible mechanisms involved in PAH-related asthma—through immunologic and oxidative stress changes; (3) the interactions between PAHs and EPHX1 involved in asthma—enzymatic activity of epoxide hydrolase 1, which affected by EPHX1 genotypes/SNPs/diplotypes, could influence human PAH metabolism and people’s vulnerability to PAH exposure. This review provided a better understanding of the above interactions and underlying mechanisms for asthma which help to raise public’s concern on PAH control and develop strategies for individual asthma primary prevention.