Growth and competition of the marine diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. II. Light limitation

The marine diatoms Phaeodactylum tricornutum (Bohlin) and Thalassiosira pseudonana (Hasle and Heimdal) were grown under both continous illumination and a 14 h light: 10 h dark cycle at light intensities ranging from 1.53×10^-4 to 2.95×10^-1 ly min^-1. Under both photoperiods, T. pseudonana exhibited higher division rates than P. tricornutum at high light intensities, but the reverse was true at all light intensities <3×10^-3 ly min^-1. Comparison of these results with available data on light-limited growth of other planktonic algae suggests that P. tricornutum may be unusually efficient at maintaining its cell division rate at low light intensity. This efficiency may contribute substantially to its success in turbid, nutrient-enriched mass algal culture systems, the only environments in which it is known to attain great numbers.Contribution No. 4086 from the Woods Hole Oceanographic Institution.