Variation of lipid class and fatty acid composition of Chaetoceros muelleri and Isochrysis sp. grown in a semicontinuous system Fabrice Pernet a , Re ´jean Tremblay b, * , Eric Demers c , Marcel Roussy d a GIROQ, Universite ´ Laval, Cite ´ Universitaire, Quebec, Canada G1K 7P4 b Centre Aquacole Marin-Universite ´ du Que ´bec a ` Rimouski, 6 rue du Parc CP 340, Grande-Rivie `re, Quebec, Canada G0C 1V0 c Centre de Technologique des Produits Aquatiques, 96 Monte ´e Sandy Beach, Gaspe, Quebec, Canada G4X 2V6 d Centre Aquacole Marin-MAPAQ, 6 rue du Parc CP 340, Grande-Rivie `re, Quebec, Canada G0C 1V0 Received 29 August 2002; received in revised form 2 January 2003; accepted 3 January 2003 Abstract The lipid class and the fatty acid composition of microalgae are of primary importance in feeding filter-feeding animals properly and variations of those parameters have never been investigated in a cultivation system applied to hatcheries. The objective of this study was to document the lipid class and fatty acid composition of the diatom Chaetoceros muelleri (CHGRA) and the flagellate Isochrysis sp. (Clone TISO) during the entire process of hatchery cultivation in relation to the period of the year (summer vs. winter). At the beginning of the cultivation process of CHGRA, in a small volume of culture, triacylglycerol (TAG), sterol, saturated, monounsaturated, and polyunsaturated fatty acids (particularly 20:5n À 3) were high, sharply dropping when volume was increased. An inverse relationship has been observed for acetone mobile polar lipids (AMPLs; pigment) and phospholipids (PLs), thus leading to no significant effect of the volume of culture on the total lipid (TL) content of CHGRA. The total lipid content of TISO increased with the volume of culture due to AMPL and PL classes and saturated and polyunsaturated fatty acids. The short- and long-term variability of lipid class composition has been observed for both species. Such results highlight the high variability of marine microalgae lipid content during the culture process and season as well. Hatchery implication is discussed. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Lipid class; Fatty acid; Microalgae; Season; Volume; Hatchery 0044-8486/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0044-8486(03)00030-9 * Corresponding author. SODIM, 137-3 rue de la Reine, Gaspe, Quebec, Canada G5X IT5. Tel.: +1-866-368- 4044; fax: +1-418-368-7541. E-mail address: Rejean.Tremblay@SODIM.org (R. Tremblay). www.elsevier.com/locate/aqua-online Aquaculture 221 (2003) 393 – 406