| The ocean is an important material basis for the survival and development of human beings, and the pollution of oil spill is the main problem affecting the marineenviron ment safety, oil spill pollution has a very serious impact on the marine ecosystem. Marine microalgaes are low-level producers in the marine ecosystem, it is the main supply of primary productivity in the ocean, also plays a key role in material cycle and energy flow in ecosystem. As an main plankton in the marine environment, the state of health of marine microalgae is closely related to the marine ecological environment. At present the study on the impact of oil on marine microalgae growth has been more widely, its basically around the oil Water-Accommodated Fraction(WAF) study the concentration changes of petroleum hydrocarbons, that "lowgrowth promoting high suppression" phenomenon [15] of planktonic microalgae, which promoted the growth of low concentration, inhibited the growth of high concentration. In the East China Sea, each big oil field exploitation are light crude oil, due to its extremely volatile characteristics, the study and previou results may have slight differences. So, this paper use the light crude oil Water-Accommodated Fraction and light crude oil experiment, the experimental study of growth rate and chlorophyll of Prorocentrum donghaiense, Heterosigma akashiwo and Skeletonema costatum under different temperature and illumination of a content, the initial understanding of light crude oil stress mechanisms of toxicity of microalgae, which will in the oil pollution on marine microalgae growth effect, fill the blank of light crude oil field, providing important technology for marine oil pollution emergency disposal, damages and integrated management.1 Effect of light crude oil WAF on the growth and chlorophyll of three marine microalgae(1)Light crude oil WAF had significant inhibitory effect on the growth of microalgae, low concentration(0.73 mg dm-3) of light crude oil WAF has a relatively small effect on microalgae growth, no significant influence compared with the control group, while the light crude oil with high WAF concentration was significantly inhibited on the growth of three species of microalgae, the same time, the higher concentration of light crude oil WAF, the stronger the inhibition.(2) On the basis of the 96-h EC50 of the light crude oil stress to three species of marine microalgae, it showed that the order of toxicity sensitivity from light crude oil WAF to three species of marine microalgae: Prorocentrum donghaiense>Skeletonema costatum>Heterosigma akashiwo.(3)The light crude oil WAF had an varying degree inhibition on chlorophyll a content of the three kinds of microalgae. The sensitivity of Heterosigma akashiwo is slightly higher than that of Prorocentrum donghaiense and Skeletonema costatum.(4) The temperature was the key factor of influencing the growth of algae and light oil WAF toxicity effect. The temperature increased, the cell density and chlorophyll content of three microalgae increased, but the difference between different light crude oil WAF concentration was also more obvious.(5) The light intensity had significant effects on the growth and chlorophyll content of microalgae. In the suitable range, the stronger the light, the faster the microalgae growth, and the higher the chlorophyll a content, but more obvious the petroleum hydrocarbon toxicity corresponding stress.2 Effect of light crude oil on the growth and chlorophyll of three marine microalgae(1) Light crude oil has the characteristics of high volatile. This experiment compared with the light crude oil WAF experiments, the initial concentration of microalgae to light crude tolerance increased 10 times as much.(2) Light crude oil has certain inhibitory effect on the growth of microalgae. Because of the high volatile of light crude oil, light oil stress inhibitory effect on microalgae growth is not obvious, each basic can resume normal growth.(3) On the basis of the 96-h EC50 of the light crude oil stress to three species of marine microalgae, it showed that the order of toxicity sensitivity from light crude oil to three species of marine microalgae: Prorocentrum donghaiense>Skeletonema costatum>Heterosigma akashiwo.(4) Through the variation of chlorophyll a content of three species of microalgae under the control of different light crude oil concentration obtained, Heterosigma akashiwo was more sensitive,.With the increase of concentration of light crude oil, the chlorophyll a content of three species of marine algae were obviously decreased, but the difference between the treatment group and the control group was significantly enhanced.(5) The temperature was the key factor of influencing the growth of algae and light oil WAF toxicity effect. The temperature increased, the cell density and chlorophyll content of three microalgae increased, but the difference between different light crude oil concentration was also more obvious.(6) The light intensity had significant effects on the growth and chlorophyll content of microalgae. In the suitable range, the stronger the light, the faster the microalgae growth, and the higher the chlorophyll a content, but more obvious the petroleum hydrocarbon toxicity corresponding stress.3 Effects of dynamic gas on the growth and chlorophyll of three species of marine microalgae(1) The experiment is different from the fourth chapter lies in continuous gas(respectively 6h, 12 h and 24 h interval), after the light crude oil volatilization, continue refueling operation directly cause light crude oil continued and increased stress effect, there is a certain effect of continuous oil spill simulation.(2) The experimental results showed that, the low concentration(10 mg dm-3) of the light crude oil inhibitory effect on microalgae growth is relatively small, compared with the control group, the effect is not significant, while the higher light crude oil concentrations on the three species of microalgae growth showed significant inhibitory effect, the same time the higher light crude oil concentration inhibit the more notable effect. An important factor in refueling frequency is also affecting the light crude oil inhibitory effect, the higher the frequency of inhibitory effect more obvious.(3) On the basis of the 96-h EC50 of the light crude oil stress to three species of marine microalgae, it showed that the order of toxicity sensitivity from light crude oil to three species of marine microalgae: Prorocentrum donghaiense>Skeletonema costatum>Heterosigma akashiwo, refueling frequency on microalgae inhibition size order: 6h>12h>24h.(4) Light crude oil stress decreased the chlorophyll content of microalgae, the frequency of gas and the more effect. With the increase of the light crude oil concentration, the chlorophyll a content of three species of marine algae were obviously decreased, the difference between the treatment group and the control group was significantly enhanced.(5) The temperature was the key factor of influencing the growth of algae and light oil WAF toxicity effect. The temperature increased, the cell density and chlorophyll content of three microalgae increased, but the difference between different light crude oil concentration was also more obvious.(6) The light intensity had significant effects on the growth and chlorophyll content of microalgae. In the suitable range, the stronger the light, the faster the microalgae growth, and the higher the chlorophyll a content, but more obvious the petroleum hydrocarbon toxicity corresponding stress. |
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