Variations In The Toxic Effects Of Petroleum Hydrocarbons To Two Marine Microalgae Species Under Different Environmental Factors

The current economic globalization has accelerated the marine oil pollution and made it one of the key problems to be addressed. Petroleum hydrocarbons exert toxic effects on marine lives, varying in different environment factors. The toxicity may vary in solubility and structure in water under different temperatures, salinities, pH values and illumination intensities.Isochrysis galbana and Platymonas helgolandica var. tsinglaoensis are selected to serve as the target organisms in this study. The main objective of this work is to compare the toxic effects of water-accommodated fraction to two species of marine microalgae under different environments in the controlled laboratory conditions, to explain how the toxic effects of WAF to two species of microalgae in mono-culture and co-culture variation with the change of environment factors. The purpose of the present study is to provide scientific basis to investigate effects of water-accommodated fraction on aquatic ecosystems, and supply theoretical evidence to study the community succession of marine microalgae and marine environmental monitoring.The results are as follows:A. Changes of WAF toxicity to two marine microalgae species in different temperatures(1) The 96hEC50 of WAF acute toxicity to two marine microalgae increase as the temperature increases from 15℃ to 25癈.(2) Study on the different population growth of two marine microalgae species in mono-culture exposed to WAF at different temperatures. The results show the different carrying capabilities (K), intrinsic growth rates (r) and the timings into stationary phases at different temperatures. To Isochrysis galbana, the intrinsic growth rates are increased and the timings into stationary phases are brought forward with the temperature increasing. To Platymonas helgolandica var tsingtaoensis, it shows the highest intrinsic growth rate and the minimum time into stationary phase at 20℃(3) Study on the different population growth of two marine microalgae species in co-culture exposed to WAF at different temperatures. The results show the different effects of the microalgal population growth at different temperatures. It shows less effect on Isochrysis galbana with the variation of temperature because of the low density of cells, about 7.5% of which in mono-culture. But it shows more effect on Platymonas helgolandica var tsingtaoensis with the variation of temperature.B.Variations in WAF toxicity to two marine microalgae species in different pH(1) Under different salinities, the toxic effects of WAF on Isochrysis galbana and Platymonas helgolandica var Jsingtaoensis were different. The WAF showed a smaller toxic effect on Platymonas helgolandica var tsingtaoensis than Isochrysis galbana in the salinity of 15-25. But the trend was opposite when the salinity was from 25 to 35.(2) Study on the different population growth of two marine microalgae species in mono-culture exposed to WAF at different Salinities. The results show the different carrying capabilities (K), intrinsic growth rates (r) and the timings into stationary phases at different salinities. Both of the two microalgae species show the maximum K and r, and the shortest time into stationary phases in the natural salinity of sea water. Both of the lower and the higher salinity make the opposite results.(3) It shows the same trend of result in mono-culture and mono-culture with the variation of salinity. But it shows more effect on Platymonas helgolandica var. tsingtaoensis than Isochrysis galbana with the variation of salinity.C. Variations in WAF toxicity to two marine microalgae species in different salinities.(1) The 96h WAF acute toxicity to two marine microalgae decreases and then increases as the pH increases from 6.5 to 8.5.(2) Study on the different population growth of two marine microalgae species in mono-culture exposed to WAF in different pH. The results show the different carrying capabilities (K), intrinsic growth rates (r) and the timings into stationary phases in different pH. Both of the two microalgae species show the maximum K and r, and the shortest time into stationary phases in the natural salinity of sea water. It shows the minimum K in the low pH of 6.5. There is no significant between pH7.5 and pH 8.5.(3)It shows the same trend of result in mono-culture and mono-culture with the variation of pH. But it shows more effect on Platymonas helgolandica var tsingtaoensis than Isochrysis galbana with the variation of pH.D. The preliminary study of the interactive effects of UV-B radiation and WAF on marine microalgae(1) The growth of the studied marine microalgae increases with either the low dose of UV-B radiation or the low dose of the WAF exposure.(2) The growth of microalgae decrease exposed at the joint impact of low dose of UV-B radiation and low density of WAF on microalgae.(3) The toxicity of WAF on microalgae enhances with the dose of UV-B radiation strengthen.