Growth Effect Of Marine Economic Microalgae In Mixed-culture Of Different Species

Phaeodactylum tricornutum belongs to Phaeodactylum,Phaeodactylales,Pennatae, Bacillariophyta;Dunaliella salina belongs to Dunaliella,Volvocales,Chlorophytaceae, Chlorophyta,and Platymonas subcordiformis belongs to Platymonas,Volvocales, Chlorophytaceae,Chlorophyta.They are rich in various high-value bioactive substances such as protein,polysaccharides and unsaturated fatty acid,hence they have been regarded as important marine economic microalgae and used widely in aquaculture.In the present study,three typical marine microalgae,Phaeodactylum tricornutum,Dunaliella salina and Platymonas subcordiformis were used as experimental materials;experiments were carried out by coculturing each two of these microalgal species in f/2 culture medium;besides,cocultures of P. tricornutum and D.salina,D.salina and P.subcordiformis under different proportions were conducted under different nitrogen concentrations(1.4 mg/L,14 mg/L and 140 mg/L) in order to investigate the growth effects of coculture of marine microalgal species with different proportions by measuring some parameters including cell density,the value of OD,the content of chlorophyll-a,biomass and the content of protein.The results showed that:1,coculture of marine economic microalgae could obviously affect the productivity of microalgal colonies. Coculture of P.tricornutum and D.salina,as well as D.salina and P.subcordiformis could obtain better growth as compared with the corresponding monoculture of those microalgal species,while the coculture of P.tricornutum and P.subcordiformis exhibited no growth of superiority when compared with the monoculture of P.tricornutum or P.subcordiformis.2, coculture of P.tricornutum and D.salina with suitable proportion under proper condition could increased total cell density,the value of OD,the content of chlorophyll-a,biomass,and the content of protein.For example,Under high nitrogen and middle nitrogen,when they were cocultured with D7:P3,chlorophyll a content was 96.7%higher than monoculture of D.salina, and 132.8%higher than the monoculture of P.tricornutum;meanwhile protein content was increased by 1.3 or 2.8 as compared to the monoculture of D.salina or P.tricornutum.3, coculture of D.salina and P.subcordiformis with suitable proportion under proper condition could significantly increased total biomass and biochemical composition.Under high nitrogen and middle nitrogen,When they were cocultured with D7:$3,chlorophyll a content was 1.17 higher than the monoculture of D.salina,and 7.77 higher than the monoculture of P. subcordiformis;protein content was increased by 19.1%and 195.3%as compared with the monoculture of D.salina and P.subcordiformis.3,nitrogen level could also influence the growth of cell colonies in the coculture.High nitrogen and middle nitrogen could evidently increase the cell density,biomass and intercellular substances,leading to a superiority of coculture.While limitation of nitrogen could remarkably restrict the growth of cell colonies in the coculture of P.tricornutum and D.salina,as well as D.salina and P.subcordiformis.These findings provide some referenced information for the large-scale cultivation,exploiture and utilization of marine economic microalgae.