Sinking rate response to depletion of nitrate, phosphate and silicate in four marine diatoms

摘要: The effect of nutrient (N, P, and Si) depletion on sinking rates was studied for two small (Skeletonema costatum (Grev.) Cleve Chaetoceros gracile Schutt) large [Ditylum brightwellii (West) Grun Coscinodiscus wailesii (Gran et Angst)] centric diatoms obtained from stock cultures. Each diatom examined under conditions (1) repletion (=log growth phase), (2) (48 h without a given substrate), (3) recovery (24h after addition limiting substrate to nutrient-deplete populations). All nutrient-replete cultures displayed low despite differences in cell size. In populations, rate related the kind depleted varied among species. Silicate elicited by far greatest increase all 4 species, indicating that biochemical aspects silicon metabolism are more important buoyancy regulation than density-related variations amount per cell. Since N- P-depletion caused lower 3 this observation calls re-evaluation axiom necessarily causes increased rates. exception wailesii, which sank faster types limitation. most cases, typical log-phase were not regained within 24 nutrient-depleted populations. Ultimately, length period may be useful identifying metabolic processes responsible actively growing cells.