Ngo Xuan Quang

Conservation of the Mekong Delta wetlands through hydrological management

The Vietnamese Mekong Delta (VMD) comprises extensive river and canal networks, both natural and man-made, and has a history of extensive land use change and development. The delta’s wetlands are under considerable ecological stress because of hydrological changes, agricultural and aquaculture development, urban and industrial pollution, climate change, and upstream water resource development. In this paper, we review the current threats and challenges to the conservation and management of the wetlands in the VMD. We recommend that the current water management practices of the Ramsar-listed Lang Sen Wetland Reserve are changed so that the natural flood regimes are reinstated and the risks to the community from forest fires are managed. Ongoing investment is needed to support further research, set up long-term monitoring, and to develop hydrodynamic models for the Lang Sen Wetland Reserve so that management and conservation efforts can achieve the specific objectives for the wetland. This approach may be useful for managing other wetlands across the VMD.

Rapidly diminishing mangrove forests in Myanmar (Burma): a review

Mangroves are a very productive ecosystem found in tropical and subtropical latitudes. Southern and south western coastlines of Myanmar host a large number of mangrove species, many under threat of extirpation. This review analyzes recent changes and the current status of mangrove vegetation along the coastline of Myanmar and key factors causing rapid reduction of mangrove coverage. Remote sensing techniques can be used to improve mangrove mapping and monitoring in Myanmar in the future. Community-based mangrove reforestation has helped restore green coastal areas to some extent, even though there are limitations due to the lack of specific biodiversity in reforested areas. Mangrove ecosystem research, conservation and restoration in Myanmar have gained new momentum after the 2010 political reform. Some urgent measures are still needed for the conservation of rapidly diminishing mangrove forests, as well as improving community-based mangrove reforestation, enhancing biodiversity, implementing sustainable aquaculture, and reinforcing environmental protection laws.

BIODIVERSITY AND DISTRIBUTION PATTERNS OF FREE-LIVING NEMATODES COMMUNITIES IN BALAI RIVER, BENTRE PROVINCE

Nematode communities in Ba Lai river, Ben Tre provi nce were investigated in September of 2015 (eight stations from estuary to u pstream). The results showed that the nematode communities have characterized by high den sity and biodiversity, providing useful information of nematode assemblages in freshwater h abitas, in particular inland river. Also the results indicated that the distribution of nematode communities in Ba Lai river was strongly discriminated between in and outside of dam with tw o groups. The Ba Lai dam may be reasons for cause the nematodes distribution discontinuity. Present study is a pioneering attempt to record the impact of the dam on benthic invertebr ate in Viet Nam.

A A COMPARISON OF THE APPLICABILITY OF THE SHANNON-WIENER, AMBI AND M-AMBI INDEX FOR ASSESSING ECOLOGICAL QUALITY STATUS OF SEDIMENT IN AN ORGANIC SHRIMP FARMING PONDS, NAM CAN DISTRICT, CA MAU PROVINCE

The Shannon-Wiener Index (H′), AZTI’s Marine Biotic Index (AMBI) and multivariate AMBI (M-AMBI) of macrofauna communities were applied for comparing their applicability in assessing the status of sediment ecological quality (EcoQ) in eight organic shrimp farming ponds (OSFP) in Ca Mau province. There were obvious differences between the evaluation results of the three indices in the eight OSFP. The EcoQ given by the AMBI and M-AMBI was higher than that given by the H’ index. This indicates that H’ index may also be more sensitive to environmental disturbances than the AMBI and M-AMBI. Furthermore, the EcoQ given by the M-AMBI was a neutralization between those given by the H’ and AMBI indices. As there were no environmental data available in this study, that the H′ index was more sensitive to environmental disturbances than the AMBI and M-AMBI has yet to be further elucidated. Further investigation of these three indices with environmental data is also needed to get a comprehensive answer to this matter. Keywords AMBI, benthic indices, H′, indicator, M-AMBI, macrofauna communities, organic shrimp farming ponds References [1] S. Bustos-Baez, C. Frid, Using indicator species to assess the state of macrobenthic communities, Advances in Polychaete Research, Springer, 2003.[2] C. J. Dauvin, T. Ruellet, N. Desroy, L. A. Janson, The ecological quality status of the Bay of Seine and the Seine estuary: use of biotic indices, Marine Pollution Bulletin 55 (2007) 241.[3] H. Teixeira, S. B. Weisberg, A. Borja, J . A.Ranasinghe, D. B. Cadien, R. G. Velarde, ... & J.K. Ritter, Calibration and validation of the AZTIsMarine Biotic Index (AMBI) for southern California marine bays, Ecological Indicators 12(2005) 84.[4] I. Muxika, A. Borja, W. 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Environmental changes near the Mekong Delta in Vietnam using remote sensing

This study is an attempt to use satellite imagery for the assessment of environmental changes near the Ba Lai River, Mekong Delta, in Vietnam. Landsat imagery was used to calculate water quality variables as well as land cover changes near Ba Lai River, both before and after the construction of an irrigation dam in 2002. A lot of changes in land use and land cover were observed in this area since the construction of the Ba Lai dam, particularly in the agricultural practice such as rotational plantation of rice and other crops. The present study stated that water quality has decreased and became polluted with organic materials between 1988 and 2006. Water quality variables such as chlorophyll (algae), nitrogen, and phosphorus were highly increased, whereas turbidity levels have slightly increased since the dam construction, possibly due to alluvial silty deposition.

Nematode communities in the Sai Gon River harbors in relation to tributyltin concentrations

The impact of toxic tributyltin (TBT) compounds was investigated on free-living nematode communities in the Sai Gon River. Samples were collected from 11 harbor stations downstream of the Sai Gon river plus one upstream station during the dry and rainy seasons. The results showed that all butyltin compound (mono-, di-, and tri) concentrations were relatively low compared to historical data from the same or adjacent estuaries, supporting the effectiveness of the 2009 ban on these products as antifouling. Nematode communities were typical for oligohaline regions showing a high spatial and temporal variability in abundance and diversity. Nematode community composition clearly differed between the two seasons, with the nematode communities being less variable in the rainy season compared to the dry season, while nematode communities differed significantly between stations. TBT values were still significantly negative correlated with nematode densities and selective deposit feeders during the dry season, partly confirming earlier experimental results on the response of nematodes to TBT. The historical presence of TBT contamination can possibly have caused a long-term impact on nematode communities in the Sai Gon river sediment, reflected in depressed densities during the dry season.

NEW DISCOVERING ON INTERNAL CORRELATION OF NEMATODE COMMUNITIES’ CHARACTERISTICS IN THE CO CHIEN ESTUARY, BEN TRE PROVINCE

Insight on internal correlation of nematode communities’ characteristicswas first investigated along the Co Chien estuary in order to understand a linkamong their densities, composition, diversity, morphometric and biomass. Researchresults showed high value in the nematode densities and diversities in thisestuary. Nematodes had medium size, individual biomass is rather small buttotal biomass in the communities is quite high due to their densities. Thenematode size, shape and biomass have significant relationship with densitiesand feeding type structure in their communities along the Co Chien estuary.

One new and two unknown species of free - living marine nematodes from Can Gio mangrove forest, Ho Chi Minh city, Vietnam

One new and two unknown species of free living marine nematodes belonging to family Oxystominidae are described from Cangio mangrove forest, Hochiminh city of Vietnam. The Oxystomina paraclavicaudata sp. nov. is characterized by the long conico-cylindrical tail with claviform tip, the double parallel spicules and the pre-and postvulval papillae. The species Litinium sp1. can be recognized by labial setae and cephalic setae follow the structure 6 + 6 + 4; amphid pear-shaped with slit-like aperture; spicules have a kink at the middle; gubernaculum short, plate-like; two papilliform supplements with short seta; tail rounded with the pore of caudal glands at the end. And Litinium sp2. is characterized by labial setae small or absent, two subcephalic setae at the posterior edge of the amphid; amphid elongate pocket-like with a fringe around the aperture; only one short somatic setae at the base of pharynx. Reproductive system diorchic with short testes; two supplement setae; only two caudal gland cells observed within the tail, the opening is shifted ventrally.