SEGH Articles

Depositional and ecological environments of the Bay of Bengal coast of northeast India

01 May 2012
Dr. Asok Kumar Bhattacharya summarises his work at the University of Calcutta on the Sundarban wetlands in India, including work on coastal sedimentology, impact of anthropogenic pollution and coastal zone management.

 

Dr. Asok Kumar Bhattacharya is a professor in the department of Marine Science,Calcutta University, India. Over the past 43 years he has been actively researching in the fields of fluviatile and coastal sedimentology, bioturbation processes and products, geomorphic and ecological changes of coastal zone by natural and anthropogenic forcing, impact of heavy metal contamination and persistent organic pollutants (POPs) in the biotic and abiotic components of Indian Sundarban wetland, and coastal zone management. The study areas belong to the siliciclastic, tropical, meso-macrotidal, low-lying coastal plains of northeast India having moderate wave climate excepting periods of tropical cyclonic surges with a wave height of about 7m.  

While working on beach processes and sedimentation, Dr. Bhattacharya discovered a ‘new record of current crescents lacking preservation of obstacles’ formed by some semi permanent globose marine algae Valonia sp. stranded on beach surface. He is also the first to name and describe the ‘backwash-and-swash- oriented current crescents’ from the beach surface useful as good indicators of beach slope (1:50 to 1:90), current direction and depositional environment.

Dr. Bhattacharya studied a large variety of surficial- and internal bioturbation structures produced primarily by polychaetes, bivalves and crabs, and indicated their importance in differentiating shore-parallel biozonation of intertidal flats.  He is the first to identify the sandy megarippled substrate preference for the carnivorous polychaete Diopatra cuprea which was well known for its preference for muddy substratum. His research has also determined  that some soft-bottom polychaetes can thrive better in most polluted substrates of Sundarban wetland and hence, well suited for undertaking biomonitoring programme towards its sustainable management.

Drs.Bhattacharya and Sarkar (see previous article Feb 2012 for Sundarban) published their research about the threat of ecological imbalance of this fragile coastal zone due to rapid depletion  of living resources like tiger prawn seeds (Panaeus monodon),and bulk of mollusks due to indiscriminate overexploitation for aquaculture farms and other areas of commercial benefits.

His research further highlighted the adverse impacts of constructions of embankments on the ecological balance of mangrove ecosystem of Sundarban wetland. It is revealed that such constructions abruptly truncate the mangrove forests occurring behind the intertidal flats to be replaced later by marsh vegetation.

Figure 1: Mining and transportation of sand from Digha beach for construction purposes

Dr. Bhattacharya’s research has addressed several issues relating to coastal inundation
and hazards faced by the poor coastal communities. Mining and transportation of beach sands (Fig.1), destruction of dune vegetation by trampling and grazing, leveling of dune tops  for constructions and open sea vistas (Fig.2) have been identified to be the major anthropogenic stresses responsible for degradation of this coast The effects of tourism and fishing by trawlers  often enhance the process of coastal degradation. Natural forcing from high waves generated by periodic cyclones often breaches the dune trains for several meters and pushes the shoreline further inland (Fig.3).

 

Figure 2: Levelling of dune tops for construction of fisherfolks’s makeshifts and avenue to open sea approach. Inundation of inland areas takes place through such avenues during high water stage causing lot of coastal pollution.

Figure 3:  Landward invasion of beach at Dadanpatrabar. The well exposed roots of coconut tree and other plant reveal a good amount of beach lowering.

 

His collaborative research with scientists of India and abroad on persistent organic pollutants (POPs) in sediment and biota of Sundarban wetland evaluated for the first time the ecotoxicological risks of this fragile ecosystem. The coastal environments of Sudarban are badly affected by multiple sources of contaminants, of which municipal sewage; effluents from agriculture, aquaculture, upland industries, deforestation, dredging and shipping traffics are the most important. POPs are hazardous because of their semivolatile nature, toxicity, persistence, long–range transport and bioaccumulation potential. Contaminations from the residues of five classes of POPs such as DDTS, HCHs , PAHs , PCBs and PBDEs in sediments and in selective biota were found to be of variable range in both vertical and lateral extensions of this wetland. The pollutant effects were assessed by use of different sediment quality guidelines. Sediment dispersal patterns, wave–tide climate, biotubational churning of sediments, atmospheric precipitation and distances from sources to sinks of pollutants were identified as the primary causes of such variability. In addition to researches on POPs, the distribution and possible source of several trace elements in sediment cores and their ecotoxicological effects have also been determined tracing their routes from sources to sinks.

 

Professor Asok Kumar Bhattacharya, Department of Marine Science, University of Calcutta. bhattacharyaasok747@gmail.com 

 

References

Overexploitation of shellfishes in northeast coast of India-A.Bhattacharya and S.K.Sarkar. AMBIO, published by Springer on behalf of Royal Swedish Academy of Sciences,  32,(1), 70-75,2003

Breaching of coastal dunes : An issue  of management  of the  coast  to safeguard  the coastal communities  of West Bengal ,India- A. Bhattacharya, A. Bhattacharya  and S.K.Sarkar. Asian Journal of Environment and Disaster Management, Singapore, 1(2),23-35,2009. DOI:10.3850/S1793924009000182

Quantification and source identification of polycyclic aromatic hydrocarbons in core sediments from Sundarban mangrove wetland, India –C.Dominguez, S.K.Sarkar,A.Bhattacharya,M.Chatterjee,B.D.Bhattacharya,E.Jover,j.Albaiges,J.MBayona,Md.A.Alam and K. K. Satpathy. Archives of Environmental Contamination andToxicology, Springer, 59(1):49-61, 2010 http//www.springerlink.com/content/132803q28210256t/

Fluvial  geomorphology of the Kupa River  drainage basin, Croatia: A perspective of its application in river management and pollution studies- Stanislav Franciscovic-Bilinski,Asok kumar Bhattacharya, Halka Bilinski, Bhaskar Dev Bhattacharya, Avijit Mitra and Sansosh Kumar Sarkar. Zeitschrift fur Geomorphologie, E.Schweizerbart’sche Verlagbuchhandlung Publishers, 55(2), DOI:10.1127/0372-8854/2011/0056

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

  • Biochar-based constructed wetlands to treat reverse osmosis rejected concentrates in chronic kidney disease endemic areas in Sri Lanka 2017-12-01

    Abstract

    The objectives were to investigate the potential remedial measures for reverse osmosis (RO) rejected water through constructed wetlands (CWs) with low-cost materials in the media established in chronic kidney disease of unknown etiology (CKDu) prevalent area in Sri Lanka. A pilot-scale surface and subsurface water CWs were established at the Medawachchiya community-based RO water supply unit. Locally available soil, calicut tile and biochar were used in proportions of 81, 16.5 and 2.5% (w/w), respectively, as filter materials in the subsurface. Vetiver grass and Scirpus grossus were selected for subsurface wetland while water lettuce and water hyacinth were chosen for free water surface CWs. Results showed that the CKDu sensitive parameters; total dissolved solids, hardness, total alkalinity and fluoride were reduced considerably (20–85%) and most met desirable levels of stipulated ambient standards. Biochar seemed to play a major role in removing fluoride from the system which may be due to the existing and adsorbed K+, Ca+2, Mg+2, etc. on the biochar surface via chemisorption. The least reduction was observed for alkalinity. This study indicated potential purification of aforesaid ions in water which are considerably present in RO rejection. Therefore, the invented bio-geo constructed wetland can be considered as a sustainable, economical and effective option for reducing high concentrations of CKDu sensitive parameters in RO rejected water before discharging into the inland waters.

  • Medical geology of endemic goiter in Kalutara, Sri Lanka; distribution and possible causes 2017-12-01

    Abstract

    This study assesses the distribution of goiter in the Kalutara District, Sri Lanka in order to find causative factors for the occurrence of goiter even after the salt iodization. A questionnaire survey was conducted at the household level and at the same time iodine and selenium levels of the water sources were analyzed. Questionnaire survey results indicated the highest numbers of goiter patients in the northern part where the lowest were found in the southern sector which may be due to the presence of acid sulfate soils. Females were more susceptible and it even showed a transmittance between generations. Average iodine concentrations in subsurface water of goiter endemic regions are 28.25 ± 15.47 μg/L whereas non-goiter regions show identical values at 24.74 ± 18.29 μg/L. Surface water exhibited relatively high values at 30.87 ± 16.13 μg/L. Endemic goiter was reported in some isolated patches where iodine and selenium concentrations low, latter was <10 μg/L. The formation of acid sulfate soils in the marshy lands in Kalutara district may lead to transformation of biological available iodine oxidation into volatile iodine by humic substances, at the same time organic matter rich peaty soil may have strong held of iodine and selenium which again induced by low pH and high temperature were suggested as the instrumental factors in the endemic goiter in Kalutara district. Hence, geochemical features such as soil pH, organic matter and thick lateritic cap in the Kalutara goiter endemic area play a role in controlling the available selenium and iodine for food chain through plant uptake and in water.

  • Nickel accumulation in paddy rice on serpentine soils containing high geogenic nickel contents in Taiwan 2017-12-01

    Abstract

    We investigated the extractability of nickel (Ni) in serpentine soils collected from rice paddy fields in eastern Taiwan to evaluate the bioavailability of Ni in the soils as well as for demonstrating the health risks of Ni in rice. Total Ni concentrations in the soils ranged were 70.2–2730 mg/kg (mean, 472 mg/kg), greatly exceeding the natural background content and soil control standard in Taiwan. Available Ni concentration only accounts for <10% of total soil Ni content; 0.1 N HCl-extractable Ni was the more suitable index for Ni bioavailability in the soil to rice than was diethylenetriaminepentaacetic acid (DTPA)-extractable Ni. The accumulation ability of rice roots was much higher than that of its shoots; however, compared with those reported previously, our brown and polished rice samples contained much higher Ni concentrations, within the ranges of 1.50–4.53 and 2.45–5.54 mg/kg, respectively. On the basis of the provisional tolerable Ni intake for adults recommended by the World Health Organization (WHO), daily consumption of this rice can result in an excessive Ni intake.