Testing the yield of a pilot-scale bubble column photobioreactor for cultivation of the microalga Rhodomonas salina as feed for intensive calanoid copepod cultures

A dual column photobioreactor (PBR) (2 x 47 L) with mixed CO2/air bubbling was tested for cultivation of the microalga Rhodomonas salina as food for live feed copepods. In the continuous growth phase, the cell density was relatively stable at 2.40 +/- 0.13 x 10(6) cells/ml at an average dilution rate of 0.46 +/- 0.02 per day throughout the 30-day experiment. The produced algae had a high content of both total fatty acids (TFA) and free amino acids (FAA). Especially, the harvested algae contained a high proportion of poly-unsaturated fatty acids that made up 80% of the TFA and of essential amino acids (35% of all FAA), implicating desirable components as feed for copepods. The current PBR was sufficient to feed a culture of the calanoid copepod Acartia tonsa at a density of 2,500 adult/L in ca. 500 L culture with a daily yield of approximately 17 x 10(6) eggs. To be able to sustain the integrated copepods production, the suggested volume of the algae cultures should be ca. 20% of the copepod culture volume.