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

  • Status, source identification, and health risks of potentially toxic element concentrations in road dust in a medium-sized city in a developing country 2017-09-19

    Abstract

    This study aims to determine the status of potentially toxic element concentrations of road dust in a medium-sized city (Rawang, Malaysia). This study adopts source identification via enrichment factor, Pearson correlation analysis, and Fourier spectral analysis to identify sources of potentially toxic element concentrations in road dust in Rawang City, Malaysia. Health risk assessment was conducted to determine potential health risks (carcinogenic and non-carcinogenic risks) among adults and children via multiple pathways (i.e., ingestion, dermal contact, and inhalation). Mean of potentially toxic element concentrations were found in the order of Pb > Zn > Cr(IV) > Cu > Ni > Cd > As > Co. Source identification revealed that Cu, Cd, Pb, Zn, Ni, and Cr(IV) are associated with anthropogenic sources in industrial and highly populated areas in northern and southern Rawang, cement factories in southern Rawang, as well as the rapid development and population growth in northwestern Rawang, which have resulted in high traffic congestion. Cobalt, Fe, and As are related to geological background and lithologies in Rawang. Pathway orders for both carcinogenic and non-carcinogenic risks are ingestion, dermal contact, and inhalation, involving adults and children. Non-carcinogenic health risks in adults were attributed to Cr(IV), Pb, and Cd, whereas Cu, Cd, Cr(IV), Pb, and Zn were found to have non-carcinogenic health risks for children. Cd, Cr(IV), Pb, and As may induce carcinogenic risks in adults and children, and the total lifetime cancer risk values exceeded incremental lifetime.

  • Erratum to: Preliminary assessment of surface soil lead concentrations in Melbourne, Australia 2017-09-11
  • In vivo uptake of iodine from a Fucus serratus Linnaeus seaweed bath: does volatile iodine contribute? 2017-09-02

    Abstract

    Seaweed baths containing Fucus serratus Linnaeus are a rich source of iodine which has the potential to increase the urinary iodide concentration (UIC) of the bather. In this study, the range of total iodine concentration in seawater (22–105 µg L−1) and seaweed baths (808–13,734 µg L−1) was measured over 1 year. The seasonal trend shows minimum levels in summer (May–July) and maximum in winter (November–January). The bathwater pH was found to be acidic, average pH 5.9 ± 0.3. An in vivo study with 30 volunteers was undertaken to measure the UIC of 15 bathers immersed in the bath and 15 non-bathers sitting adjacent to the bath. Their UIC was analysed pre- and post-seaweed bath and corrected for creatinine concentration. The corrected UIC of the population shows an increase following the seaweed bath from a pre-treatment median of 76 µg L−1 to a post-treatment median of 95 µg L−1. The pre-treatment UIC for both groups did not indicate significant difference (p = 0.479); however, the post-treatment UIC for both did (p = 0.015) where the median bather test UIC was 86 µg L−1 and the non-bather UIC test was 105 µg L−1. Results indicate the bath has the potential to increase the UIC by a significant amount and that inhalation of volatile iodine is a more significant contributor to UIC than previously documented.