Effect of algal addition on stability of fatty acids in enriched Artemia franciscana

Abstract

In Artemia franciscana, enriched for 24 h with emulsified lipids, thefatty acid DHA (22:6ω3) is unstable. In rotifers the level of DHA canbe stabilised by adding algae rich in DHA to the fish tanks. To test thismethod for A. franciscana, enriched A. franciscana was incubated with thealga Isochrysis galbana, which is rich in lipids and DHA, at sixconcentrations ranging from 1 to 20 mg C l⁻¹ at 13–14°C. After lipid enrichment, A. franciscana contained15% lipids of which 79% (116 mg g DW⁻¹) werefatty acids. Of the fatty acids, 17% was DHA (19.8 mg gDW⁻¹). After 72 hours incubation with I. galbana, the level ofDHA decreased to 1.6–3.2 mg g DW⁻¹, which was areduction by 84–92%. This was independent of the algalconcentration. The amount of total fatty acids decreased to 53–73 mg gDW⁻¹, a reduction by 37–54%, independent of thealgal concentration. The rates of loss of the fatty acids, and especiallyDHA, was greater during the first 24 h at the highest algal concentrations(8, 10 and 20 mg C l⁻¹). Enriched A. franciscana shouldtherefore not be incubated with high algal concentrations (>6 mg Cl⁻¹) during first feeding of marine fish larvae.