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This study aims to evaluate the diversity of rotifers in various freshwater habitats in Da Nang City, Vietnam, and to investigate the relationship between community structure and environmental conditions. A total of 75 rotifer species belonging to 25 genera and 17 families were recorded, out of which seven species are new to Vietnam. Species from the families Brachionidae and Lecanidae are abundant (containing about 50% and 69.44%, respectively) in the total rotifer species in both lacustrine and riverine habitats. The number of rotifers recorded in the lakes (64 taxa) was much higher than those in rivers (36 taxa), and this is possibly due to the conditions in lakes being more favorable for the development of small zooplanktons. The significant influences of environmental factors (temperature, pH, turbidity, and trophic state) on the rotifer community were well-reflected in the distribution of commonly found species in lakes (p-value < 0.05). Our study results enrich the data on the diversity and the ecology of rotifers in Vietnam.

This study investigated the presence of microplastics in two common edible bivalves in Vietnam, the hard clam (Meretrix lyrata) and the undulate venus clam (Paratapes undulatus), from two estuaries in Da Nang city. Microplastics were detected in both species with relatively high concentrations—from 2.17 ± 0.43 to 2.38 ± 1.28 items g−1 in the undulate venus clams and from 4.71 ± 2.15 to 5.36 ± 2.69 items g−1 in the hard clams. Fibers were the most dominant form of microplastic in both clams, and a high proportion were fibers with sizes from 300 μm to 1500 μm. An estimation of microplastic intake in Vietnamese consumers’ bodies from clam consumption was made, which showed an average ingestion of 2489 items person−1 year−1. Our study is also the first global record of microplastic distribution characteristics in the undulate venus clam Paratapes undulatus.

The marine microalgae Dunaliella salina holds significant economic value due to its rich content of β-carotene, a natural pigment with high antioxidant capacity, immune-stimulating properties, and a crucial role in antioxidant reactions with vitamins C and E. This study evaluated the effects of light factors on the growth and biosynthesis of β-carotene in the Dunaliella salina strain isolated from coastal waters in Central Vietnam. The microalgae strain was cultured in the static f/2 medium at 25°C, under different light spectra (blue, red, and white) and light intensities (13.5, 27.0, and 40.5 µmol photon/m2/s), with a similar light/dark cycle of 16/8. The results indicated that the microalgae strain showed the highest growth rate and production yield of β-carotene under the red LED light, whereas the highest β-carotene accumulation in each microalgal cell was obtained under the blue LED light. Regarding light intensity, the best growth and β-carotene production yield was observed under the highest experimental light intensity of 40.5 µmol photon/m2/s, but the highest β-carotene content per algal cell was reached under the lowest intensity (13.5 µmol photon/m2/s). These findings provide important scientific data for further research to identify the optimal conditions for increasing biomass and stimulating the accumulation of valuable secondary compounds of the microalgae Dunaliella salina in Vietnam.