In this study, a field survey of fecal contamination indicators and Clostridium perfringens cpe(+) in river environments was conducted to verify the effectiveness of C. perfringens cpe(+) as a microbial source tracking indicator in public water bodies. In the Saijo River, which serves as a model of point source contamination from human sewage effluents, the concentrations of Escherichia coli, enterococci and C. perfringens increased after the inflow of sewage effluents, with the cpe-positive prevalence rate of C. perfringens isolates increasing from 13.3 to 21.5%. In the Nagaike River, contaminated with household sewage effluents from non-point sources, high concentrations of E. coli, enterococci, and C. perfringens cpe(+) were detected, with high cpe-positive prevalence rates of 27.6 and 26.4%. Contrarily, in the Koayu River, which is contaminated with treated wastewater from a large swine farm, an increase in the concentration of fecal contamination indicators and C. perfringens was observed; however, the cpe-positive prevalence rate of C. perfringens isolates remained unchanged, ranging as low as 3.6 and 3.9%. Altogether, our results revealed that the concentration and pollution load of C. perfringens cpe(+) is an effective microbial source tracking indicator of human fecal contamination in freshwater environments.

The extensive global use of bisphenols (bisphenol A (BPA) and its analogs) is of serious concern to human health and aquatic ecosystems. Aquatic plants and rhizosphere microorganisms can largely affect the environmental fate of bisphenols. In this study, the association between common reed, which is distributed widely in the aquatic environment, and microorganisms existing in the surrounding area of its roots was studied to illustrate its capabilities and possible mechanisms for the removal of five different bisphenols (BPA, bisphenol F, bisphenol P, bisphenol S, and 4,4ʹ-thiodiphenol). Different experimental systems were prepared in the presence and absence of sterile common reeds and aquatic microorganisms. The effects of common reed and microorganisms on the removal of bisphenols differed across compounds. However, the removal of all the bisphenols tested was clearly accelerated in the co-presence of common reed and microorganisms, which indicated the importance of aquatic plant-microorganism association in enhancing bisphenol removal. The results of this study further revealed the major contribution of the distinct mechanism of removal of each bisphenol by the association between common reed and microorganisms.

Thraustochytrids such as Aurantiochytrium are heterotrophic and produce valuable fatty acids (FAs) and therefore expected as a tool for removal of organic compounds in wastewater and simultaneous production of FAs. The four strains of Aurantiochytrium sp. were isolated from the mangrove leaf samples, and among these the strain L3W showed the high specific growth rate of 0.27 1/h at 25°C. In addition, this strain grew at the ranges of temperature from 15°C to 35°C, pH from 3 to 9, and salinity from 0.3 to 70 PSU. Under the optimal condition of 25°C, 30 PSU, and pH7, the strain L3W produced 270 mg/g of FAs including 135 mg/g of docosahexaenoic acid, 11 mg/g of pentadecanoic acid and 9.3 mg/g of margaric acid. Furthermore, the strain L3W produced these FAs at pH3 and pH9. The pH and salinity tolerance of the strain L3W might be advantageous in its application for production of valuable FAs under competition with other microorganisms in unsterile wastewater.

The aim of this study was to survey the behavior of water quality and surface sediment during the growth period of submerged macrophytes. Their dynamics were investigated by a microcosm experiment. In midsummer, the nitrogen and phosphorus concentration of the column with vegetation (Column A) was kept low and the inorganic nitrogen loading in the first 15 days was about 3 times lower than that of the column without vegetation (Column B). The vegetated column prevented algal blooms in midsummer and was checked to see zooplankton and zoobenthos during the biological active period. The rate of change of masses of carbon and nutrients in the sediment before and after the column experiment were calculated on the basis of the contents of each and sediment thickness (0 to 5 cm). Masses of organic carbon in Column A and Column B in the sediment after 100 days were estimated to decrease by 14 and 23%, respectively. Masses of nitrogen in Column A and Column B in the sediment after 100 days were estimated to decrease by 11 and 26%, respectively. Thus, the mass reduction rate of the vegetated column was 10 to 16% less than that of the column without vegetation.