Effects of light path lengths and initial culture density on the cultivation of Chaetoceros muelleri (Lemmermann, 1898)

In the cultivation of a marine diatom Chaetoceros muelleri (Lemmermann, 1898), flat plate vertical glass reactors with light path lengths of 1 or 3 cm were used in the laboratory under a constant photon flux density (PFD) of 190 mumol photon m(-2) s(-1). In the first experiment, equal inocula were added in the two bioreactors (1 and 3 cm light path); by the end of the second day, cell concentration was low in the 1-cm light path bioreactor, possibly indicating photoinhibition, since growth of the culture increased in the 3-cm light path bioreactor. As for in the second trial, the areal volumes were equal, that is, the cell concentration was increased three-fold in 1 cm light path to equalize the areal optic densities in both reactors. After the harvest started, average of the volumetric output rates in 1 cm (P-V1 (cm)) and 3 cm light paths (P-V3 (cm)) were calculated to be 0.22 and 0.10 g l(-1) day(-1), and areal output rates in 1 cm (P-A1 (cm)) and 3 cm (P-A3 (cm)) light paths were calculated to be 1.80 and 2.53 g m(-2) day(-1), respectively. The optimal population density was obtained by a daily harvest of 5% of culture volume to be 2.39 g m(-2) day(-1) in 1 cm light path and 3.27 g m(-2) day(-1) in 3 cm light path. Light path length of 3 cm was found optimal in both with low and high initial cell densities. (C) 2003 Elsevier Science B.V. All rights reserved.