Environmental impacts of impoundments on mangrove ecosystem, at Cangio, Hochiminh City, South Viet Nam

The study was conducted to assess the environmental impacts the impoundness, a method of shrimp culture, on mangrove ecosystem and recommend the appropriate management scheme that is environmentally, socially, and economically acceptable. It considered three general subsystems of mangrove ecosystem, namely, the biological, physico-chemical, and socio-economic. Significant differences between IN and OUT the impoundments of the various bio-physical and the socio-economic component were tested. On the physical-chemical component, the study showed that there were significant differences between inside and outside the impoundments, the former being higher from the latter in terms of water transparency, total suspended solids, salinity, PO4, SiO2, Ca2+, Mg2+. The study also showed that there were no significant differences between inside and outside the impoundments in terms of water temperature, DO, BOD5, NH4+, NO3-, and NO2-, and soil properties. On the biological component, the study results showed that there were significant differences in terms of mean quantities of Phytoplankton, Gross Primary Productivity, Zooplankton, and Benthos between inside and outside the impoundments. The lower quantities were collected inside the impoundments. There were no correlationships among Gross Primary Productivity, zooplankton, benthos. Impoundment implementation caused the death of some parts of Sonneratia and Avicenia inside the impoundments. On the socio-economic component, the study showed that there were many positive changes in the improvement of living conditions due to the high income derived from impoundments, in the pattern of natural resource use, and in the environmental awareness of the participants. The high level of satisfaction of the respondents reflected the positive results of impoundment application this demonstrated that there are the positive impacts on the community as reflected in the social and economic acceptability of the impoundments integration on the mangrove forest ecosystem at Cangio, Hochiminh City, South Vietnam. Results show that the new policy on Land Allocation and Forest Care Taking Contract has accomplished both targets: (1) the demand on land use of local community to develop shrimp farming, and (2) the efficient conservation of mangrove forest ecosystem, has been initially successful