The gross chemical composition and fatty acid composition of 18 species of tropical Australian microalgae for possible use in mariculture

The gross chemical composition and fatty acid composition of 18 species of tropical Australian microalgae (2 cryptomonads, 8 diatoms, 3 prasinophytes, 4 prymnesiophytes and a rhodophyte) grown under standard conditions (pH 8.3±0.2, temperature 25±1°C, photon flux density 80±2 μ mol m −2 s −1 and salinity 25±1‰ and harvested in late log phase of growth), were determined as part of a program to find species for use as feed in tropical aquaculture. Protein was the major component of all species (range 24.2–47.1% dry weight) except diatoms (range 19.4–36.7% dw). Highest lipid contents were found in Cryptomonas sp. CRFI01 and Isochrysis sp. NT14 (22.0 and 23.4% dw, respectively). The highest percentage of soluble carbohydrate was found in Rhodosorus sp. CS249 (20.2% dw), while diatoms had the highest amounts of ash (range 21.2–38.8% dw). Moderate levels of the polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were found in Cryptomonas sp. CRFI01 (12 and 6.6% of total fatty acids, respectively). Moderate levels of EPA were also found in Chaetoceros sp. CS256 and in Skeletonema species GOC27 and GOC36. DHA was most abundant in Isochrysis sp. NT14 (9.9% total fatty acids) and Cryptomonas sp. CRFI01 (6.6% total fatty acids). The highest amount of arachidonic acid (AA) was found in Fragilaria sp. GOC52.