A partial substitution of microalgae with single cell detritus produced from seaweed ( P orphyra haitanensis ) for the nursery culture of tropical oyster ( C rassostrea belcheri )

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus ( SCD ) production from seaweed ( P orphyra haitanensis ) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters ( C rassostrea belcheri ) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 10 4 cell mL −1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD , or 100% microalgae ( P  < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed ( P . haitanensis ) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.