Date of Award
Doctor of Philosophy in Biological and Environmental Sciences
Integrative and Evolutionary Biology (IEB)
Fisheries, Animal and Veterinary Science
Michael A. Rice
Indonesia is well known for abundant aquatic resources, both marine and freshwater, including fishes, zooplankton and phytoplanktonic microalgae. However, relatively little information is available about microalgal resources despite their potential to be used as live feed in the hatchery phase of aquaculture of a number of marine species. The use of local microalgae is desirable in local hatcheries because they tend to grow better with high yield under local conditions, thus reducing the risk of culture crash and production cost while preventing disease vectors that may introduced by foreign microalgae strains. In this dissertation, the potential of Indonesian microalgae to be used in shrimp hatcheries is investigated by isolating and growing the microalgae from Kendari Bay and Wanggu River estuary in South East (SE)-Sulawesi, Indonesia, under controlled conditions, assessing the growth of shrimp larvae using the local isolates as food and measuring the nutritional content of these local microalgal isolates.
Four strains of microalgae were successfully isolated using flow cytometry and the micro-pipet isolation technique. Those strains are denoted as Kb1-2 identified as Chaetoceros sp, Kb1-3, Kb1-5 and Kb2-6 identified as Melosira cf moniliformis. Melosira cf moniliformis was excluded from the microalgal growth experiment due to its larger cell size which were >10 μm. The growth for 15 days and cell size of those strains was investigated under four different salinities, 20, 25, 30 and 35 psu and growth rates were compared to the growth of T-ISO (Tisochrysis lutea), Chaetoceros neogracile and Tetraselmis chui. Salinity did not affect the growth of Indonesian microalgae, similar to T. chui, Ti. lutea and C. neogracile, but did affect microalgal final density. Two Indonesian microalgal strains, Kb1-3 and Kb1-5, had the highest yield, among all microalgae tested, whereas, yield of Kb1-2 was similar to Ti. lutea and C. neogracile. Cell sizes of three of the four Indonesian microalgae ranged from 1.2-11.8 μm, considered a suitable size for shrimp larvae which is <20 >μm The Indonesian strains may be potential for mass culture and to be used in shrimp hatcheries based upon the cell sizes, their ability to survive long culture periods and tolerate a wide salinity range.
The subsequent experiment to assess the suitability of the Indonesian microalgae strains as food for hatchery-reared white shrimp (Litopenaeus vannamei) larvae confirmed that Indonesian microalgae may be suitable as food for white shrimp larvae, supporting performance similar to that of well-established strains in terms of weight gain, ingestion rate and food conversion index. However, lower survival was observed in shrimp larvae fed on Indonesian strains compared to T. lutea and C. neogracile. Analyses of the nutritional content of Indonesian microalgae revealed that lipid, protein and carbohydrate contents of these strains in late log and stationary phase of growth and were comparable to T. lutea during the stationary phase of growth. Of Indonesian microalgae, Kb1-2 contained important ω-3, eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA) and ω-6, arachidonic acid (ARA) when cultured at 25 and 35 psu. Kb1-3 strain contained ARA, EPA and DHA only when cultured at 35 psu whereas Kb1-5 only when cultured at 25 psu. Indonesian microalgae, Kb1-3, had a higher ARA concentration compared to other Indonesian strains and T. lutea. DHA in Indonesia microalgae was similar to T. lutea but T. lutea had a higher concentration of EPA. This suggests that the use of Kb1-2 and Kb1-5 strains in white shrimp hatcheries may be best when cultured at 25 psu and Kb1-3 at 35 psu to supply necessary PUFA at optimal cells density. Other options is mixing these strains with other species, such as T. lutea, that contain higher levels of essential EPA.
Iba, Wa, "The Potential of Indonesian Microalgal Strains to Support Eastern White Shrimp (Litopenaeus vannamei) Aquaculture" (2016). Open Access Dissertations. Paper 500.