[Spatiotemporal Distributions and Ecological Risk Assessments of Typical Antibiotics in Surface Water of Taihu Lake].

Using solid phase extraction-high performance liquid chromatography tandem mass spectrometry, antibiotics belonging to four classes (i.e. sulfonamides, quinolones, tetracycline, and macrolides) in the surface water of Taihu Lake were monitored monthly for a year. Moreover, the potential ecological risks of antibiotics in Taihu Lake were assessed. During the one-year monitoring, all the eighteen target antibiotics were detected to some extent in the surface water. The detection rates of five sulfonamides (sulfamethoxazole, sulfathiazole, sulfadiazine, sulfadimethazine, and trimethoprim) were higher than 50%. The concentrations of quinolones in the surface water were relatively higher. The average and medium concentrations of ciprofloxacin were 13.0 ng·L-1 and 13.5 ng·L-1, respectively. There were significant differences in the antibiotic pollution during the different months, with the average concentrations of the target antibiotics ranging from 7.3 to 33.5 ng·L-1. The concentration levels were lower from June to October, while higher concentrations were observed from February to May and in November. In the surface water of Taihu Lake, the spatial variations of antibiotics among the 20 sampling sites were not significant, with the average concentrations ranging from 13.0 to 14.3 ng·L-1. During the one-year monitoring, the rates of medium and high risks that the antibiotics posed to algae reached 57.5%. The ecological risks of antibiotics were more severe in April and November, and the quinolones may be the dominant risk factor. This issue should be carefully considered by management authorities.

Study on the cyanobacterial toxin metabolism of Microcystis aeruginosa in nitrogen-starved conditions by a stable isotope labelling method.

In this study, the biosynthesis of microcystins (MCs) was investigated after long-term nitrogen-starved conditions in cyanobacterium Microcystis aeruginosa. The results demonstrated that the algal cells were able to survive in a non-growing state with nitrogen starvation for more than one month. The physiological properties of the algal cells were studied to elucidate the mechanisms of viability under nitrogen-deprivation conditions. After the state of nitrogen chlorosis, new toxins could be resynthesized and tracked using 15N-stable isotope-labelled nitrogen. Nitrogen starvation of nutritionally replete cells resulted in a significant increase of microcystin-LY (MC-LY), thereby suggesting that MC-LY may undergo catabolism to provide nitrogen or that MC-LY may be produced to play an important role in the cell in response to nitrogen deprivation. The rank order of different types of nitrogen in algal cells assimilation was N-ammonium > N-urea > N-nitrate > N-alanine. The relationship between the production of toxin variants and various environmental conditions is an interesting issue for future research and may help improve the understanding of the ecological role of cyanobacterial toxins.

[Evaluating eutrophic state of Taihu Lake by in situ hyperspectra].

In situ experiments including water quality analyzing and spectra measuring were conducted on Jun., 2004 and Aug., 2004 in Taihu Lake for 21 samples. Then eutrophic state of Taihu Lake was evaluated by measured hyperspectra data, and the evaluating index was eutrophic state index (TSI). Firstly, the simulation model of water reflectance was built by analytic model using inherent optical properties (IOPs). Then Chlorophyll a content (Chl-a) was inversed by optimizing method by Matlab software; Secondly, TSI was calculated by inversed Chl-a, and the eutrophic state of Taihu Lake was evaluated by using ArcView' s interpolation function. The evaluation figures show that: there are notable differences between Jun., 2004 and Aug., 2004. The proportion of mesotropher state is as high as 61% in June, while the proportion of light eutrophic is as high as 52% in August. In totally, the most serious eutrophic state occurs in north of Taihu Lake. Eutrophlic state wears off from north to south. The lowest eutrophic region is in the east of Taihu Lake.