Effect Of Environmental Factors On Microcysis And Its Toxin Production

Nowadays,the frequency and grade of blue-green algae that cause water bloom are increasing rapidly. Microcysis is not only the dominant algae in eutrophic water, but also a toxin-producing algae that can produce Microcystins.Effect of water environment and nutrient substances on the growth and toxin production of Microcysis has been attacking high research attentions in algae field. However, no agreement on the influence of environment on toxin production mechanism has been reached yet. This paper explored the effect of nitrogen, phosphorus, temperature and illumination on growth and toxin production of Microcysis,( 1) The environmental factor such as temperature, light, nitrogen and phosphorus were studies to determine their effects on the growth and microcystin production of Microcysis aeraginosa by using single factor analysis. Each factor for 23 days test, determination of every other day by calculating algae cell and the chlorophyll a,while microcystin-LR was analyzed by high-performance liquid chromatography.The result indicated that the most favorable conditions for the growth was the temperature of 30℃ and the light intensity of 1000 Lux,but it produced the most toxin under 25℃、500 Lux.In addition, M. aeraginosa amount and MC-LR content increased with the increase of nitrogen. Phosphorus is a probable limitation nutrient factor, and a low concentration will satisfy the growth and toxin production of M. aeraginosa. The N:P atomic ratio at 100:1 was determined as the optimum for growth and toxin production.(2)The relationship of different combinations of temperature, light, nitrogen and phosphorus with the growth and toxin production of Microcysis was explored through orthogonal test. Verdigris microcystin algae for 29 days test, determination of the algal cell density and every other day algae liquid absorbance to reflect its biomass change, every three days to determine its production of algal toxins- LR.Results showed that light intensity influences growth of Microcysis mostly, followed by temperature, total nitrogen(TN) and total phosphorus(TP) successively. Light intensity affects the toxin production of Microcysis most significantly, followed by TP, TN and temperature successively. 200 Lux light intensity, 22 ℃temperature, 20 mg·L-1 TN and 0.6 mg·L-1 are the optimum toxin production conditions of Microcysis.