Effect Of Nitrogen And Phosphorus Nutrients On Growth And Azaspiracid Production Of Azadinium Poporum

In recent years, the harmful algal blooms (HABs) frequently occur in coastal waters worldwide, lots of harmful marine algaes gathered in some sea areas will not only exacerbate seawater eutrophication but also release a variety of marine algal toxins, polluting offshore aquaculture environment and threating to consumers’health. As we know, Azaspiracids (AZA) is a newly discovered marine algae toxin. Recently azaspiracids contaminated seafood poisoning (AZP) outbreaks frequently worldwide, which causes widespread concerns. Now more than 30 kinds of AZA toxins and their derivatives have been found and identified, some marine algae species producing AZA toxins also have been found, which mainly include Azadinium spinosum、A. poporum and A. obesum. Although AZP has not been reported in China now, related studies find that A. poporum distributes widespread in China coastal waters. In general, people know and study AZA toxins later in China, and there are less reports about the effects of environmental factors on growth and AZA toxins production of Azadinium genus. Therefore, this thesis selects two strains A. poporum AZDY06 and AZFC22 isolated from the South China Sea for the study, discussing effect of different nitrogen and phosphorus nutrients on their growth and AZA toxins production. The experimental results show that:(1) A. poporum AZDY06 and AZFC22 show positive responses to changes of nitrate and phosphate concentrations. With nitrate and phosphate concentrations increasing, the growth rate and the maximum cell density of algae strains both also increase in a certain range of concentrations. The growth cycle of AZFC22 is shorter than AZDY06 in batch culture. Two A. poporum strains also show some differences for the needs of nitrogen and phosphorous nutrients:compared with AZFC22, AZDY06 is more adapted to high concentration of nitrate and less adapted to high concentration of phosphate.(2) A. poporum can grow normally in inorganic nitrogen (nitrate) medium and organic nitrogen (urea) medium, but they have relative higher specific growth rates and shorter growth cycle in organic nitrogen medium than inorganic nitrogen medium. It shows that the two algaes can utilize both inorganic and organic nitrogen source for cell division and proliferation, while the organic nitrogen urea is more conducive to the rapid growth of dinoflagellates.(3) AZA cell quota of A. poporum AZDY06 and AZFC22 in stable growth phase are higher than exponential phase under different nitrogen and phosphorus concentrations. AZFC22 producing AZA-2 toxin level is higher than AZDY06. In exponential phase, A. poporum mainly utilize nutrients for rapid cell division and proliferation, their toxin anabolic slowly, resulting in lower AZA cell quota. In stable growth phase, algal cells stop proliferation and nitrate concentrations change has no significant effect on AZA cell quota, while phosphate concentrations change significantly affects AZA cell quota and phosphorus restrictions can stimulate and improve toxin production capacity of A. poporum. By comparing AZA content of unit volume of two A. poporum strains’medium under different nitrogen and phosphorus nutrients, we find that it is necessary to consider the growth status and toxin production level of dinoflagellates comprehensively in order to obtain the maximum amount of toxins in algae cultivation process.The study results of the thesis reveal preliminarily the effect of different nitrogen and phosphorus nutrients on growth and azaspiracid production of A. poporum AZDY06 and AZFC22, which has important significance for the further optimization of A. poporum’s in indoor culture conditions and obtaining amount of azaspiracids.