Stable Isotopic Composition Of Red Tides Algae In The Process Of Red Tide

In order to explore the occurrence mechanism and the new ideas of monitoring and prevention of red tide, under the laboratory condition, this study selected the typical red tide algae,Alexandrium tamareme, Gymnodinium aerucyinosum Stein, Skeletonema costatum and Nitzschia closterium as experiment material, under the cultured in Conway medium, simulated a complete algal bloom process and examined the important monitoring index (biomass, nutrient concentration) of the four kinds of red tide algae (belong to diatoms and dinoflagellates) to find out the rule of the correlation with stable isotope characteristic value in different growth stages. Cultivation process is divided into single and two kinds of different combination of mixed culture, on this basis,we analyze the similarities and differences of the rule of biomass, nutrient concentration and carbon and nitrogen stable isotope composition in the process between the single and the mixed cultivation.Theoretical basis is the process of red tide with nutritional status changes,such as carbon source and nitrogen source changes, the selective absorption of red tide algae to elements source will lead to the dynamics of carbon and nitrogen stable isotope fractionation, namely when nutrient elements is sufficient, red tide algae can absorb priority level lower 12C and 14N, nutritional deficiencies when is forced to absorb the heavier 13C and 15N.The experimental results show that the algae growth process can be obviously divided into four stages:the adaptation phase, the logarithmic phase,the stable phase and the decline phase; Nitrogen and phosphorus nutrient concentration have a downward trend with training time and well correlation with the biomass,nitrogen source absorption depends on the kinds of micro algae,whether the relative concentrations of different nitrogen source in the external environment to achieve the optimal concentration for micro algae to absorb, compared with the nitrogen source, the demand for phosphorus source of micro algae is relatively small, four experiment algae all have the ability on phosphate storage capacity; Little silicate consumption of Dinoflagellates in the process of proliferation,but it is the essential element to diatom; In the process of a complete red tide occurrence, stable isotopic composition of carbon (δ13C) shows a decreasing trend or basic stability with time, and nitrogen stable isotope composition (δ15N) showed increasing trend; Compared with single cultivation, the trend of 815N has not changed under mixed cultivation,it shows the higher and wider value scope and good correlation with biomass and the change of nitrogen source, the change trend of δ13C showed no obvious fractionation phenomenon during the process of carbon absorption, but has the higher value.Therefore, the stable isotope composition can both provide new indexes and possible new methods for the red tide monitoring and provide certain data base to preliminary explore the mechanism of red tide.