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The spatiotemporal variation of phytoplankton and their relationship with environmental variables were analyzed in the Saigon River—a tropical river in Southern Vietnam. Two longitudinal profiles were conducted during dry and rainy season at 18 sampling sites covering more than 60 km long in the river. Besides, a bi-weekly monitoring conducted in the upstream, urban area (Ho Chi Minh City—HCMC), and downstream of Saigon River was organized from December 2016 to November 2017. The major phytoplankton were diatoms (e.g., Cyclotella cf. meneghiniana, Leptocylindrus danicus, Aulacoseira granulata), cyanobacteria (Microcystis spp., Raphidiopsis raciborskii, Pseudanabaena sp.), and euglenoids (Trachelomonas volvocina). Commonly freshwater phytoplankton species and sometimes brackish water species were dominant during the monitoring. Phytoplankton abundances in dry season were much higher than in rainy season (>100 times) which was explained by a shorter riverine water residence time and higher flushing capacity during the dry season. There was a clear separation of phytoplankton abundance between the urban area and the remaining area of Saigon River because of polluted urban emissions of HCMC. Redundancy analysis shows that the environmental variables (TOC, nitrogen, pH, salinity, Mo, Mn) were the driving factors related to the dominance of L. danicus and Cyclotella cf. meneghiniana in the upstream river and urban section of Saigon River. The dominance of cyanobacterium Microcystis spp. in the downstream of Saigon River was related to higher salinity, Mg, Cu concentrations, and lower concentrations of nutrients, Mn, Co, and Mo. The dominance of potentially toxic cyanobacteria in Saigon River possesses health risk to local residents especially upon the increasing temperature context and nutrient loading into the river in the next decades. [ABSTRACT FROM AUTHOR]

Hermetia illucens, the so-called black soldier fly (BSF), has been reported as an important insect in treating domestic and agricultural manure wastes. With the ability to live well in the environment of decomposition or waste containing a variety of substances, many types of microorganisms can be related to the intestinal microflora, helping the larvae digest, grow and develop well, even creating protection against parasites and pathogens. The present study aimed to identify the microbial community associated with larvae and determine the dominant species in their intestine. To understand the role of intestinal microflora of BSF larvae for partly explaining the excellent treatment and the ability to live well in the waste environment, denaturing gradient gel electrophoresis (DGGE) and DNA sequencing methods were conducted in three parts of BSF larval intestine. The results indicated that the appearance of 11 dominant bands of larval intestinal microflora. Moreover, by using sequence alignment and phylogenetic analysis, our research has clearly classified seven specific strains of bacteria found in BSF larval intestine including Clostridium amazonese, Clostridium sporogenes, Clostridium tertium, Clostridium saccharolyticum, Actinomycetaceae, Dialister sp. and Dygonomonas. In particular, Clostridium is the most dominant genus compared to other groups and present in all three parts of larval intestine. The results obtained in this study provided insight into the bacterial community composition of black soldier fly larvae that can be used in the environmental, agricultural, and biomedical industries. [ABSTRACT FROM AUTHOR]