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Abstract. Indrayani I, Haslianti H, Asmariani A, Muskita WH, Balubi M. 2020. Growth, biomass and lipid productivity of a newly isolated tropical marine diatom, Skeletonema sp. UHO29, under different light intensities. Biodiversitas 21: 1498-1503. Light is one of the important factors affecting growth and biochemical composition of microalgae. The aim of this study was to determine growth, biomass and lipid productivity of a newly isolated marine diatom, Skeletonema sp.UHO29 under different light intensities. The Skeletonema sp. was cultured in 300 mL conical flasks containing 150 mL of f/2 medium under three different light intensities (28, 60 and 110 μmol photons m-2 s-1 ) with three replications. The cultures were incubated under ambient room temperatures, and a cycle of 12 hours light and 12 hours dark, in batch modes for two weeks. The results showed that the highest specific growth rate (0.56 d-1) was achieved at the highest light intensity (110 μmol photons m-2 s-1) and the lowest (0.11 d-1) was obtained at the lowest light intensity (28 μmol photons m-2 s-1). The highest biomass yield (0.62 g L-1) and biomass productivity (0.34 g L-1 d-1) was achieved at the highest light intensity. However, the highest lipid yield (0.175 g L-1), lipid content (28.78% ash-free dry weight) and lipid productivity (0.067 g L-1 d-1) were achieved at medium light intensity. The alga prefers high light intensity for higher growth rate and biomass productivity but it produces more lipids at medium light intensity. This study indicated that the Skeletonema sp.UHO29 is a potential species for outdoor mass cultivation and is a promising microalgal strain for use as a biodiesel feedstock due to its high growth rate, high biomass and lipid productivity.

The attachment of epiphytes on culture equipment and seaweed thalli has proven to be one of the factors preventing Eucheuma denticulatum growth. This research aimed to clarify epiphyte preference for E. denticulatum thallus and culture equipment by using vertical nets. Vertical net is a cultivation technology that protects seaweeds from herbivorous pests (fish and turtles). This research was conducted at Tanjung Tiram Coast, one of seaweed cultivation areas in Southeast Sulawesi Province, Indonesia. This research used vertical nets and E. denticulatum thalli. The study took place at 3 stations, each using 3 tools and 3 replications. The results showed that there were 7 species of epiphyte attaching to the vertical net equipment and 6 species attaching to the thalli of E. denticulatum. The densities of epiphytes attaching to the vertical net equipment and E. denticulatum thalli were 110 ind./cm2 and 250 ind./cm2 on average, respectively. Statistical analysis showed no significant difference in density between the epiphytes attached to the vertical net equipment and those attached to the E. denticulatum thalli. They also showed that the epiphyte density insignificantly influenced the overall seaweed weight. Correlation analysis showed a significant correlation between the abundance of epiphytes attached to the vertical nets and brightness.

Striped eel catfish (Plotosus lineatus) are fish that live in coastal waters but there are also those that live in river mouths. This study aimed to determine the growth and survival rate of striped eel catfish fingerlings at different sizes in controlled media. This study used a completely randomized design (CRD) with three treatments (different sizes) and three replications, so there were nine experimental containers. The treatments used were treatment A: maintenance of fingerlings size (3.5-4.0 cm); treatment B: maintenance of fingerlings size (4.9-5.6 cm); and treatment C: maintenance of fingerlings size (7.0-8.0). During maintenance, absolute length gain, relative growth rate, specific growth rate, and fingerlings survival were determined. The results showed that fingerling size had a significant effect on growth performance and survival. Fingerlings measuring 4.9-5.6 cm had the highest growth performance, while fingerlings measuring 7.0-8.0 cm showed the highest survival rate than other sizes. This indicates that the fingerlings measuring 4.9-5.6 cm and 7.0-8.0 cm are suitable for aquaculture.

Eucheumatoid cultivation continues to expand with a variety of methods that can increase production. This chapter will discuss an innovation in seaweed cultivation of the genus Eucheuma, which is the prime marine commodity in the tropical regions of the world. Research conducted during 2015-2017 and 2019 in Southeast Sulawesi Province, Indonesia, provided an overview of the use of floating cage that showed very significant growth results. The research result showed that the growth rates of Eucheuma denticulatum and Kappaphycus alvarezii in floating cage seemed faster and resulted in better thallus morphology. Daily production of E. denticulatum and K. alvarezii that were cultivated in floating cage was higher than daily production of E. denticulatum and K. alvarezii cultivated on longline. Specific growth rate (SGR) of E. denticulatum and K. alvarezii cultivated by using floating cage method was also higher than E. denticulatum and K. alvarezii cultivated by using longline method. Moreover, the cultivation by using floating cages produces good growth rates with no effect of herbivore attacks.