Diatoms, one of the most important groups of microalgae, widely used in aquaculture, play an important role in marine trophic networks and carbon sequestration due to their biomass rich in essential nutrients and their high growth rate. This study provides new insights into the physiological performance of Chaetoceros sp., strain CHX1, a coastal diatom isolated from Todos Santos Bay, Baja California, Mexico. Batch cultures of CHX1 were used by triplicate in Erlenmeyer with 800 ml of “f” medium, maintained at 21 °C with continuous irradiance (100 μmol m-2 s-1). Growth rate, dry weight, fatty acids profile, pigment content, and photosynthetic parameters were measured at exponential, stationary, and late stationary growth phases. Dry weight was measured gravimetrically, fatty acids with gas chromatography, pigments spectrophotometrically, and photosynthetic activity with a PAM fluorometer.
The growth rate of CHX1 at exponential growth phase was 1.9 divisions day-1, and the generation time was 0.7 days. During the late stationary growth phase, the cells underwent morphological changes, accompanied by alterations in their fatty acid profile and photosynthetic parameters. In the late stationary phase, a drop in pH was observed due to a decrease in the photosynthetic activity of the diatoms (Fig. 1).
The polyunsaturated fatty acids (PUFAs) and pigments (Chl a, Chl c, carotenoids) content per cell was higher in the stationary growth phase than in the exponential and late stationary phases.
In the exponential phase, higher values of growth rate, α, and Fv/Fm were observed (Table 1). The variations in the photosynthetic parameters of Chaetoceros sp. (strain CHX1) are attributed to the growth phase and the type of cells in the cultures. At the late stationary phase, the cells began a resting or dormant process, which led to a decrease in these physiological parameters. The preliminary results show high growth rate, elevated PUFA content, and high irradiance tolerance (Ek) make Chaetoceros sp. strain CHX1 a species with significant potential for aquaculture applications