Salt‐tolerant plant growth‐promoting rhizobacteria (ST‐PGPR) are known as potential tools to improve rice salinity tolerance. In this study, we aimed to investigate the plant growth‐promoting rhizobacteria community richness of the paddy rice fields in Soc Trang and Ben Tre Provinces where were seriously affected by sea level rise. The salinity in the sampling sites ranged from 0.14‰ to 2.17‰ in November 2018, the rainy season. The microbial abundance of samples was evaluated by spreading the samples in tryptic soy agar (TSA) medium supplemented with various concentrations of NaCl. With the increase of salt concentration up to 10% NaCl, a total number of bacteria decreased for all the samples, ranging from 106 to 104 CFU/g, and bacterial colonies were not observed at 30% NaCl. Among a total of 48 salt-resisting bacteria isolated from the rice paddy field mud surrounding the rice root, 22 isolates were able to produce indole-3-acetic acid (IAA: phytohormone for the plant growth). Seventeen out of 48 isolates were able to grow in the medium without nitrogen or phosphor sources. Six isolates having high IAA producing activity, nitrogen fixation and phosphate solubilization were belonged to Bacillus (DT6, LT16, and LHT8), Halobacillus (DT8), Aeromonas (LHT1), and Klebsiella (LHT7) genera. All the sequences of the strains DT6, DT8, LT16, LHT1, LHT7, and LHT8 were registered in the GeneBank with the accession numbers MK335670, MK335671, MK335672, MK335673, MK335674, and MK335675, respectively.

No abstract

The bloom forming cyanobacterium Microcystis aeruginosa is known to produce cyclic heptatoxins (microcystins, MC) which can be toxic to human and animal health. In this paper, we present the results of the determination of microcystin concentrations in the water environment of the Hoan Kiem lake that is the famous location in the center of Hanoi city. The High Performance Liquid Chromatography (HPLC) was used to determine the MC concentrations in water and water bloom samples of the Hoan Kiem lake. The phytoplankton community in the lake composed, mostly of genus Microcystis forming dense mats on the water surface. Two toxin types were extracted and preliminarily identified as microcystins-LR and RR. The HPLC analytical results showed that the total microcystin content varied between 2.08 and 46.00 µg MC/L. The microcystin contents were higher in dry season (from December/2008 to March/2009) than in rainy season. The occurrence of the toxic cyanobacteria that produce hepatotoxic microcystins as well as microcystin concentrations in the Hoan Kiem lake provide an important information to public health officials. These findings show that it is necessary to monitor the occurrence of toxic cyanobacteria and their toxins in surface water in Vietnam.

Environment quality, especially aquatic environment is increasingly being interested. This paper presents the initial results of dissolved heavy metal of the monthly observations for the period from January to October 2012 at Yen Bai, Ha Noi, Hoa Binh and Vu Quang stations in the Red River system. The monitoring results showed that the heavy metal concentrations in the Red River water varied in a high range: Cu: 10-80 µg/l; Zn: 2-88 µg/l; Cr: 0.2-5.1 µg/l; Pb: 2-107 µg/l; Cd: : 2-12 µg/l; Mn: 2-35 µg/l; Fe: 160-950 µg/l. Most of the mean values of heavy metal contents at the four monitoring sites were lower than the ones of the Vietnamese standard limits for surface water quality, QCVN 08:2008/BTNMT. However, at several time during the observation period, the contents of some heavy metals such as Fe, Cd and Pb exceeded the Vietnamese standard limits. The results showed that the water quality of the Red River needs more be frequently and systhematically observed.

No abstract