Isolation and growth of eight strains of benthic diatoms, cultured under two light conditions

We isolated seven strains of benthic diatoms from three abalone commercial fishery areas in the state of Baja California and in the proximity of several hatcheries and nursery. In all the cases, we isolated several strains of the genus Nitzschia and one strain of Amphiprora paludosa var. hyalina. Monospecific and non-axenic cultures of each strain were maintained on batch cultures under white and blue light at high (150 mu E m super(-2) s super(-1)) photon fluence rates. For all the diatoms we observed that the growth rate ( mu ) in the second or third day of culture had high values of duplicated strains per day. We compared the growth rate of these strains with a control specie Navicula incerta, a strain used as food in several abalone farms in Mexico, and found similar growth rates in some of the cases. For each strain, a covariance analysis was used to compare growth using white versus blue light wavelength. No significant differences in growth were observed between the two light conditions. We obtained high growth rate for Amphiprora paludosa var. hyalina with almost double values of those obtained with of the control species N. incerta and the others strains: N. thermalis var. minor, N. fonticola var. pelagica and N. frustulum var. perminuta. The sub-strains of N. laevis exhibit equal growth rate and nearly 50% less than that of N. incerta. Our results suggest that some strains of benthic diatoms offer a good potential for use in feeding abalone post-larvae, because they can be cultured under high light irradiance apparently without photoinhibition and may exhibit high growth rates and high cell concentrations.