This study surveyed and analyzed samples of aquatic insects at 10 pondst Binh Hung Hoa biological system on March and August in 2015. The results recorded 31 species belonging to 24 families, 6 orders, include Coleoptera, Diptera, Odonata, Hemiptera, Ephemeroptera and Trichoptera. In particular, the larvae of theory derdiptera had the best diversity of composition, wise distribution and high density. However, the larvae of t h e order ephemeroptera and order trichoptera had the least diversity and low level of density and distribution at maturation ponds. Among ponds, the diversity and density of aerobic pond and sedimentation pond were high while the maturation ponds were low. The composition of aquatic insects had high similarity in the same function ponds and low similarity in the different function ponds. The species composition diversity and abundance of aquatic insects were the highest in the sedimentation pond and lowest in the other ponds. In the rainy season, the species composition diversity of aquatic insects were higher than those in the dry season.

These zooplankton samples and water samples were taken at 4 sites in the fish pond area (2 outside points in the river and 2 inside point in the fish pond). The results were recorded 76 zooplankton taxa which were belong to 28 genuses and 3 phylums (Protozoa, Rotifera and Arthropoda: Cladocera, Copepoda, Ostracoda). The Rotatoria phylum was dominated over 70% of species composition and 45% of individual density. The zooplankton communities in the outside were more diverse than those in the fish ponds. Besides, there was a significant difference between the individual density of the inside and outside ponds. The Shannon-Wiener diversity index showed that the water qualities were from lightly to moderately polluted at all points. Water of inside pond was polluted by organic materials, with the dominated by Brachionus genus. The Bray – Curtis similarity showed that the difference between zooplankton communities of inside and outside ponds was about 40%. Therefore, the fish pond water could affect natural water sources.

Natural enviroment of the destroyed zone in Can Gio mangrove by Durian typhoon had been serious bioturbation. The researches about the environment of this area and role of organisms are very important for the mangrove regeneration. There are 19 species of Brachyuran crabs belonged to 13 genus, 7 families such as Sesarmidae, Ocypodidae, Varunidae, Oziidae, Grapsidae, Leucosiidae and Camptadriidae. Perisesarma eumolpe is the dominated species and effects mangrove leaf litter decomposition in there. They consumed all of 3 Rhizophora apiculata leaf types and the brown leaf is the most consumed by them. The consumed leaf rate is 5.2% - 24.44% / wet weight leaf on 24 hours. Perisesarma eumolpe is the important link of the nutritional chain in this ecosystem. They help to return the nutrition for sediment, reduce the leaf litter mass which is lost by tide.

The study was conducted to determine the presence of cellulose-degrading microorganisms which were living in the stomach of Perisesarma eumolpe crabs. P. eumolpe were collected in the gap of Can Gio mangrove caused by Durian typhoon in 2006. The study identified 520 microorganism samples from 30 stomach samples Cellulose degrading microbacteria were isolated on three types of nutrient media: meat extract – peptone, Gause and Czapek – Dok with CMC. These 520 microbial samples included of 496 aerobic bacteria, 7 actinomycetes and 0 mold samples. The number of cellulose degrading microorganisms was also accounted for 46% of total (240 samples). Among these, there were 24 bacteria strains and 5 actinomycetes strains which degradated cellulose based on the difference in the colony and the cell shape. The average microbial density per crab gut was approximately 0.66 ×105 to 6.6 ×105 cell/mL. In addition, the results showed that cellulose degrading microorganism groups have importantly contributed to the food sources for P. eumolpe during their living in the mangrove forest.

Species composition and characteristic of zooplankton communities in treated leachate of Dong Thanh landfills and in Rach Tra river (receiving the wastewater of Dong Thanh landfills) were surveyed monthly from 11/2012 to 04/2013. The results from those two areas were compared to find out the difference of the zooplankton communities. 122 species of 36 genus, 10 classes, 3 phylums and 6 types of larva were identified, of which Rotatoria acounted for 52 %. The result of Cluster analysis showed that there was a distinct difference between the zooplankton community intreated inside the landfills and Rach Tra river. The zooplankton community inside the landfills characterized by low quantity of species but high individual density. The main species composition was Rotatoria and Protozoa with good adaptation of organic and microbiological pollution of water. On the other hand, the zooplankton community in Rach Tra river characterized by communities in natural aquatic habitat with the relative balance of zooplankton groups, diversity index and dominance index were average levels.