| Coastal and coral reef ecosystems are very important providers of habitats for many organisms and environmental goods and facilities for humans.Though many natural drivers are responsible for ecological risks,various anthropogenic activities also contribute to aggravation of prevailing natural ecosystems pressures and disturbances.At present more than 25 sectors with many stakeholders are engaged in economic activities exploiting and using the resources of the coastal and marine areas(EEZ)of Bangladesh.Every day thousands of gallons of effluents are being dumped into the river from the industries located on the riverbank,without any treatment which poses severe threats to all the aquatic organisms.The present study is,the first of its kind in Bangladesh,to measure the concentrations of trace elements in water,surficial sediments,fish and shell fishes of all the major rivers,estuaries and to assess the environmental risk in the East coast mainland and an economic and ecosystem service valuation for the St.Martin’s Island since the pollution risks are less on this Island because it is far from the mainland industrial growth belt.However,a large number of tourists visit St.Martin’s Island and there is huge risk of ecological and environmental destruction of the only coral island of Bangladesh.An appreciation of the economic and ecosystem service value,would put the policy makers in a better position to develop an appropriate plan for the entire coast.The Contingent Valuation(CV)method was used to estimate the economic benefits of conserving and effectively manage human activities on St.Martin’s Island,one of the ecologically critical areas(ECAs)of Bangladesh.The use-values associated with the direct utilization of ecosystem services are estimated in this study.The coral reef and associated ecosystem contribute more than 27 million USD annually to the local economy from fishing,tourism,shoreline protection,seaweed culture and gleaning(gathering of intertidal shellfish).The two major economic sectors i.e.,tourism and fisheries generate 8.2 million USD/year and 19.4 million USD/year respectively,based on the direct use values of resources.The indirect use value of shoreline protection is estimated to be about 180,000 USD/year.The anticipated value of benefits from the oceanic resources on Saint Martin’s Island for the next 25 years,with a 6.5%discount rate,total up to 17.5 million USD.In many developing countries,including Bangladesh,the government budget is insufficient to meet the costs of the conservation and management of protected marine areas,so conservation finance is needed from other sources.The present study revealed how much tourists are willing to pay(WTP)to visit the Island to determine the value of the collected funds that could be used for the conservation and management of St.Martin’s Island.Results suggested that a significant percentage,viz.75.5%of respondents,were willing to pay an average of BDT 200(USD 2.50)as a conservation fee for a single visit to the Island In contrast 24.5%of respondents said that they would not be in favour of payments which was viewed as a protest bid.Regression analyses showed that several variables had a statistically significant impact on the amount visitors would pay as an entrance fee.An entry fee system has been proposed that will enhance the government’s meager conservation budget and its investment in social benefits and will engage the local community in promoting sustainable tourism and the conservation of the Island.Prospective risk assessment was carried out for the East coast starting from Chittagong to St.Martin’s Island to determine the current and future environmental conditions which could have adverse effects on the ecosystem due to the massive infrastructure and recent development programme planned by the government of Bangladesh.Water samples were collected from rivers,estuaries,the coast,and the open ocean for analysis of physicochemical parameters,viz.temperature,dissolved oxygen(DO),biological oxygen demand(BOD),total suspended solids(TSS),pH,and nutrients including nitrate,nitrite,phosphate,ammonia and silica.Risk quotient(RQ)values were higher than one for almost all the environmental parameters in the rivers and coastal areas of the entire East coast.Contaminations of heavy metals in surface sediments of Karnaphuli,Sangu,Bakkhali and Naf River,Kutubdia and Moheshkhali Channel,and St.Martin’s Island were analyzed and the consequent ecological risks also assessed.The mean concentrations of Cr,Pb,Cu,Zn,As and Cd in sediments of all the sampling stations were found to be 33.41,32.34,42.03,72.67,23.75 and 1.53 mg/kg dw,respectively.Indices used in this study show that the contaminated sediments have negative effects on the aquatic ecosystems.The Pollution Load Index(PLI)value ranged between 0.45 and 1.67,which indicates the severity of trace-element contamination.The mean geoaccumulation index(Igeo)values showed that the sediment fell within the range from uncontaminated to heavily contaminated class.The Enrichment Factor(EF)values suggest that the sediments were contaminated by anthropogenic sources,and Potential Ecological Risk(PER)values demonstrate the risk in the following order,from greatest to least:Bakkhali River,Moheshkhali Channel,Karnaphuli River,Sangu River,Kutubdia Channel,Naf River,and St.Martin Island.Analyses of heavy metals in water,fish and crabs and human health risk assessment were carried out for the East coast starting from Chittagong to St.Martin’s Island.The concentrations of trace elements in water samples were much higher than the guideline values for the maintenance of aquatic life.Indices like estimated daily intake(EDI),non-carcinogenic risks such as Target Hazard Quotient(THQ),Hazard Index(HI),carcinogenic risks such as target cancer risks(TR)reveal that concentrations of heavy metals in some rivers and coastal areas pose great risks for riverine and coastal aquatic ecosystems as well as human health.However,in the open ocean,pollution levels were lower because of mixing and dilution effects.The present study revealed that lack of adherence to accepted water quality standards for the coastal,estuarine,and marine water has effectively exacerbated the effects of discharging of untreated wastewater into the rivers,estuaries and coastal areas of the entire East coast of Bangladesh.Environmental,ecological and human health risk assessment reveals that the rivers,estuaries and coastal areas need immediate measures to address the grave environmental degradation situation so that coastal areas of the East coast could be restored,conserved and managed efficiently.A coupled socio-ecologicalpolitical-restoration and management framework has been developed for St.Martin’s Island.As a first step towards the environmental restoration of the eastern regions of Bangladesh the relevant government departments should come forward and use the newly developed framework to conserve,manage and restore the degraded ecosystem of St.Martin’s Island. |
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