| As a pigment protein of cyanobacteric, phycocyanin is one of important parameters in water quality and cyanobacterica blooms monitoring. In order to obtain more accurate information on cyanobacteria, taking Microcystic aeruginosa cultured indoor as reference, the paper first analyzed influences of experimental condition and method on the extraction of phycocyanin, and then identified the extraction method and process of phycocyanin in water samples of Meiliang Bay, Taihu Lake. Meanwhile, based on four field data sets collected in spring and summer,2011, paper analyzed the absorption property and concentration variation of phycocyanin, and its relationship with chlorophyll-a concentration. Besides, paper analyzed apparent optical properties of water body, and then developed a model for phycocyanin concentration using regression analysis. The research can provide a basic support for monitoring cyanobacteria blooms and the water-color remote sensing of inland lake.The conclusions are listed as below:(1) The extraction of phycocyanin in water sampleTaking cyanobacterica bloom water samples collected on August 20,2011, the phycocyanin extraction method including freeze thawing cycle, ultrasonic wave extracting, cell-melting and acetone were compared based on absorption spectrum and phycocyanin concentration. The results showed that the freeze thawing cycle method had a better extraction efficiency and is recommended as a basic method for phycocyanin extraction from cyanobacterica blooms water samples in Taihu Lake.Beisdes, the order of the PBS addition, freezing temperature and freezing times were different between algal samples indoor and natural water samples. Extraction efficiency of natural water samples was higher when PBS added before freezing, freezing temperature was-50℃, and freezing times was between 9 and 11.(2) The absorption property of phycocyanin in different seasonsSeasonal variations were observed in absorption property of phycocyanin at the same sample site. In spring, absorption property was mainly influenced by non-algae particles and the peak at 620 nm was not observered, its absorption property was similar with non-pigmented particles. While in summer, siganificant absorption peak of phycocyanin appeared in 620nm. The maximum absorption peaks positon of water sampls shifted between 604nm and 628nm. Affected by chlorophyll protein complexes, phycocyanin specturm of some water samples collected on August 20 appeared the second peak near the 670 nm. Besides, the absorbance decreased exponentially with the increase of wavelength from 350nm to 500nm in phycocyanin absorption spectrum, and its decreased rate was different.(3) The variation of phycocyanin concentration and relationship between the phycocyanin and chlorophyll-a in different seasonThe spatial distribution and variation of phycocyanin concentration showed the seasonal change in each sample site. In spring, phycocyanin concentration and its variation were low, and there was no obvious difference in spatial distribution. The phycocyanin concentration in summer was higher than that in spring. The total concentration of phycocyanin extraction from water samples collected on July 30 and August 20, varied from 0.03 to 2.55mg/L and 0.03 to 61.96mg/L respectively. The highest value of phycocyanin concentration was recorded near to Zhihu Port on August 20. In addition, the phycocyanin concentrations in southwestern of Meiliang Bay were all lower than 0.1 mg/L.In general, chlorophyll-a concentration increased with the phycocyanin concentration, but the increase rate in different site changed. Correlation between phycocyanin concentration and chlorophyll-a concentration was not significant in spring samples. Contrarily, there were significant linear correlation relationship in summer samples, and the correlation coefficient in August 20 was higher than that in July 30. This shows that the phycocyanin concentration can indicate well on cyanobacterial blooms.(4) The apparent optical properties of the water and model for phycocyanin concentrationMeiliang Bay, Taihu Lake, has typical optical properties of inland water. Seasonal variations were observed in Lake Taihu, e.g. in spring, it was mainly influenced by non-algae particles, while in summer, and it was mainly influenced by phytoplankton. According to the relationship between RrsN (normalized Rrs by its integral calculated over 400nm-700nm) and phycocyanin concentration,460nm,620nm,709nm and 670nm were selected as sensitive bands for phycocyanin concentration of Meiliang Bay in summer, and the difference of R624 with spectrum baseline has a better correlation with phycocyanin concentration in the water. |
PDF Full Text Request