Dry weight, carbon, c/n ratio, hydrogen, and chlorophyll variation during exponential growth of selected microalgae species used in aquaculture.

Microalgae are commonly used as food source in aquaculture, mainly for shellfish and larvae ofcrustacean and fish. All hatcheries need an excellent inoculum to produce high-quality microalgae when cultured outdoor in extensive systems, and this depends largely on the health of the microalgae cultured under laboratory  conditions as a primary step. Therefore, the aim of this work was to assess variations of dry weight, carbon, C/N ratio, hydrogen and chlorophylls as physiological indicators of nutrients uptake and growth rate during exponential growth of Isochrysis galbana, Chaetoceros calcitrans and Dunaliella tertiolecta, using f/2 as culture medium.Chaetoceros calcitrans and D. tertiolecta had higher carbon content (~30 pg cell-1). The C/N ratio varied widely, gradually decreasing on I. galbana. Chlorophyll a varied among the three microalgae tested, ranging from 0.25 pg cell-1. Growth rate was higher in I. galbana (K’ 0.83) followed by D. tertiolecta and C. calcitrans. Results showed that nutrient incorporation by cell change when cell density increases; this information providesnew insights in the physiology of marine microalgae and confirms that nutrient uptake dynamics is different in each microalga species. Finally, this study indicates that using one culture medium is not equally efficient for all microalgae used in aquaculture since each species has specific nutritional requirements.