Immobilization of twelve benthic diatom species for long-term storage and as feed for post-larval abalone Haliotis diversicolor

In a survey of diatom species in hatcheries for small abalone Haliotis diversicolor, 33 species of diatom were identified. Among them 12 species of benthic diatom were isolated to form monospecific cultures that were successfully entrapped in alginate beads for long-term storage. The immobilized diatoms remained alive and maintained their capacity to multiply after 1 year of storage in absolute darkness at 4 °C without liquid media. These diatoms were subsequently applied as feed to cultivate post-larvae of H. diversicolor. Growth and survival of the post-larval abalone were examined when they were fed different species of diatoms. Nitzschia grossestriata yielded the best post-larvae harvest (average 112.6 individuals/1000 cm2), in contrast to Cocconeis scutellum, which produced the lowest harvest with an average of 7.7 individuals/1000 cm2 only. Diatoms components analysis showed that Caloneis platycephala had the highest protein content (17.4% dw). Lipid and bound EPS were the highest in Seminavis gracilenta (20.3% dw and 1188.24 pg/100 μm2, respectively). N. grossestriata had the highest soluble EPS at 212.31 pg/100 μm2. Diatom species with a combination of sufficient lipid (7–13.7% dw) and soluble EPS (ca. 50–212 pg/100 μm2) contents produced the best survival (harvest) rate of post-larvae.