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The blue-green microalgae Arthrospira was firstly introduced in Vietnam in the 1970s. Until now, the production of Arthrospira is still far from meeting the growing demand for dietary supplements, feeds, and biofertilizers. It was a paradox that most Arthrospira production plants located in the Northern provinces were characterized by cold winter with a temperature of about 10–15°C while only a few production plants in the South where the climate was favourable for large-scale production year around. Therefore, it is necessary to have better strategies and suitable techniques to increase productivity and yield. Based on the data obtained from the investigation, the production areas of Arthrospira should be set up in the South rather than in the Northern regions to take advantage of the natural condition for better yield. This paper outlines the history, current situation, and prospects of Arthrospira production in Vietnam.

This study characterized the carbon and phosphorus composition of buffalo manure, its compost and vermicompost and investigated if presence of bamboo biochar has an effect on their chemical and biological reactivity. The four substrates were characterized for chemical and biochemical composition and P forms. The biological stability of the four substrates and their mixtures were determined during an incubation experiment. Their chemical reactivity was analyzed after acid dichromate oxidation. Biological reactivity of these substrates was related to their soluble organic matter content, which decreased in the order buffalo manure > compost > vermicompost. Phosphorus was labile in all organic substrates and composting transformed organic P into plant available P. The presence of biochar led to a protection of organic matter against chemical oxidation and changed their susceptibility to biological degradation, suggesting that biochar could increase the carbon sequestration potential of compost, vermicompost and manure, when applied in mixture.

Periphytic diatom communities’ colonization patterns were studied at three sampling stations of the Red–Nhue–Tolich hydrosystem presenting different urban pollution levels by using artificial substrates for 6 weeks in dry season 2005. Structural characteristics of periphytic diatoms developed on glass substrates at each sampling site were followed and compared. This experiment showed, through various general criteria (total diatom density, dry weight biomass) and specific criteria (relative diatom abundances, indices) that the structure of benthic diatoms developed on these substrates was strongly affected by pollution as early as the second week of colonization. Communities exposed to heavily and moderately polluted sites contained species which are known to be saprophilous or tolerant to organic pollution such as Nitzschia umbonata , Nitzschia palea , Cyclotella meneghiniana , Eolimna minima . Growth inhibition of diatom communities at the heavily polluted site was mostly related to a strong increase of organic load rather than to low metallic input, though metallic (Cd and Zn) burdens have been successfully quantified in the biofilms developed at the three studied sites. Nevertheless, no significant difference in species richness and diversity index between colonization duration times was observed. Based on values of diatom indices Indice de Polluosensibilite (IPS) and diatom assemblage index to organic water pollution (DAIPo), water quality could be classified as medium quality at Red site, polluted at NT 2 and heavily polluted at TL. Thus, the use of diatoms as a tool for water assessment appears suitable for monitoring rivers in Vietnam, as it is in several other countries.