초록
<P>Cell density and fatty acid (FA) content of <I>Pavlova lutheri</I> and <I>Chaetoceros muelleri</I> were analysed in a continuous algal production system (250-L bags) with reduced diameter. The cell density and FA content and composition in the algal production system were determined in replicate bags over a period of 5 weeks. The results showed that the cell density and essential FAs increased during the experiment for both species. After 5 weeks the mean cell numbers had increased to 6.0 ± 0.3 × 10<SUP>6</SUP> cells mL<SUP>−1</SUP> in the <I>P. lutheri</I> bags and 6.0 ± 0.4 × 10<SUP>6</SUP> cells mL<SUP>−1</SUP> in the <I>C. muelleri</I> bags. The content of total FAs increased significantly (<I>p</I> < 0.05) in all of the bags during the experiment. At the end of the experiment the mean total FA content were 2.7 ± 0.3 pg cell<SUP>−1</SUP> in the <I>P. lutheri</I> bags and 1.8 ± 0.1 pg cell<SUP>−1</SUP> in the <I>C. muelleri</I> bags. Maximum total FA content registered was 3.0 pg cell<SUP>−1</SUP> in one of the <I>P. lutheri</I> bags. The content of the essential FAs (ARA, EPA, DHA) increased over time in both of the species. At the end of the experiment the content of EPA (0.6 ± 0.1 pg cell<SUP>−1</SUP>) and DHA (0.3 ± 0.0 pg cell<SUP>−1</SUP>) were highest in the <I>P. lutheri</I> bags, while ARA (0.1 ± 0.0 pg cell<SUP>−1</SUP>) was highest in <I>C. muelleri</I>. EPA and DHA constituted 22% and 11%, respectively, of total FA content in <I>P. lutheri,</I> while ARA constituted 6% of total FA content in <I>C. muelleri</I>. The results from this experiment indicate that flagellates such as <I>P. lutheri</I> perform better in narrow bags with improved light conditions, while diatoms like <I>C. muelleri</I> perform better in wider bags under light limitation. Implications for bivalve hatcheries are discussed.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s10811-011-9655-6) contains supplementary material, which is available to authorized users.</P>