The effect of Ditylum brightwellii (Bacillariophyceae) on colony development of bloom forming species Phaeocystis globosa (Prymnesiophyceae) under nutrient-replete condition

To improve our knowledge of the factors regulating Phaeocystis globosa colony formation, the effects of the diatom Ditylum brightwellii on P. globosa colony development were investigated using co-culture and cell-free filtrate approaches. The co-culture experiments showed the moderate abundance of D. brightwellii significantly increased the number and size of colonies, whereas a dramatically decreased effect from high abundance of D. brightwellii. The low abundance of D. brightwellii promoted early formation of P. globosa colony. The cell-free filtrate experiments indicated that culture-filtrates from the exponential phase of D. brightwellii were stimulatory for P. globosa colony formation with more and bigger colonies formed, whereas an inhibitory effect from its senescence phase filtrates. D. brightwellii may influence P. globosa colony formation by regulating the growth of P. globosa solitary cells. Our results suggest that D. brightwellii influences P. globosa colony development, but its effects vary according to its concentrations and growth phases.

Automated summary

The study investigating the effects of diatom Ditylum brightwellii on Phaeocystis globosa colony development found that moderate abundance of the diatom increased the number and size of colonies, while high abundance had a decreased effect. The cell-free filtrate experiments showed that cultures from the exponential phase of D. brightwellii stimulated P. globosa colony formation, while filtrates from the senescence phase had an inhibitory effect. D. brightwellii influences P. globosa colony formation by regulating the growth of P. globosa solitary cells.