Nannochloropsis sp. has been identified as sources of live feed and pigment in aquaculture. To increase the production, the optimal environmental conditions for microalgae are required. Light intensity is one of the important factors that significantly affects the biomass and pigment of microalgae. The study aimed to determine the effect of light intensity (1,500; 3,000; and 4,500 lux) on growth, biomass production, chlorophyll-a, and carotenoid content of Nannochloropsis sp. strain BJ17. The results showed that different light intensities significantly affected the growth, biomass, chlorophyll-a and carotenoid contents of Nannochloropsis sp. strain BJ17. Increasing light intensity resulted in the increase of the growth rate, biomass, chlorophyll-a, and carotenoid contents of Nannochloropsis sp. strain BJ17. The cell achieved the highest specific growth rate of 1.729 /day and the cell concentration of 43.333×10 6 cell/mL at a light intensity of 4,500 lux. The highest chlorophyll-a and carotenoid concentrations of algae were obtained at 4,500 lux (8.304 µg/mL and 3.892 µg/mL, respectively). This study suggested that increasing light intensity led to the increase in the growth, biomass, chlorophyll-a, and carotenoid content of Nannochloropsis sp. strain BJ17.Keywords: carotenoid, chlorophyll, biomass, growth rate, light intensity ABSTRAK Nannochloropsis sp. diketahui sebagai sumber pakan alami dan pigmen pada budidaya perikanan. Budidaya pada kondisi lingkungan yang optimal diperlukan untuk meningkatkan produksi mikroalga. Intensitas cahaya merupakan salah satu faktor esensial yang secara signifikan mempengaruhi biomassa dan pigmen mikroalga. Tujuan penelitian ini adalah untuk menentukan pengaruh intensitas cahaya yang berbeda (1.500, 3.000, and 4.500 lux) terhadap pertumbuhan, produksi biomassa, klorofil-a, dan karotenoid Nannochloropsis sp. strain BJ17. Hasil menunjukkan bahwa intensitas cahaya yang berbeda berpengaruh secara signifikan terhadap pertumbuhan, biomassa dan klorofil-a dan karotenoid Nannochloropsis sp. strain BJ17. Semakin tinggi intensitas cahaya maka laju pertumbuhan, biomassa, kandungan klorofil-a dan total karotenoid Nannochloropsis sp. strain BJ17 semakin tinggi. Laju pertumbuhan spesifik tertinggi 1,729 /hari dan konsentrasi sel maksimum tertinggi 43,333×10 6 sel/ mL dihasilkan pada intensitas cahaya 4.500 lux. Konsentrasi klorofil-a (8,304 µg/mL) dan karotenoid (3,892 µg/mL) tertinggi juga diperoleh pada intensitas cahaya 4.500 lux. Studi ini menunjukkan bahwa peningkatan intensitas cahaya berperan dalam meningkatkan pertumbuhan, produksi biomassa, klorofil-a, dan karotenoid Nannochloropsis sp. strain BJ17.

Phytoplankton is a source of natural feed for shrimp cultivation in the pond. Phytoplankton productivity increases by the increasing nutrient content in the pond. Feed and metabolic waste is the sources of nutrient for phytoplankton growth. This study aimed to evaluate productivity and identify phytoplankton at intensive whiteleg shrimp, <em>Litopenaeus vannamei </em>cultivation system. This study was conducted at three intensive whiteleg shrimp located in Probolinggo, East Java. Samples were collected on the early and the late of culture period (day 17 and 87 after stocking). Four environmental parameters including total of ammonia nitrogen (TAN), nitrate, orthophosphate, total of suspended solid (TSS), and chlorophyll-a were measured. Identification and density of phytoplankton were also performed of each pond. The result showed that productivity of three ponds was 22,893.83 kg/ha to 23,600.61 kg/ha with an average size 12.74 g to 14.35 g. During culture period, the concentration of TAN, TSS and chlorophyll-a tended to increase. Meanwhile, the average of both nitrate and orthophosphate tended to decline. Several phytoplankton identified in this study were in the genus of <em>Oocystis, </em><em>Chlorella, Nannochloropsis, Chaetoceros</em>, <em>Stephanodiscus, </em><em>Nitzschia, Coscinodiscus, Cyclotella </em>and <em>Ulothrix. </em>Phytoplankton of the group Chlorophyta is predominance for pond 1 and 2, while pond 3 was dominated by phytoplankton in the group of Diatom/Baccillariophyta. This study indicated that the present of phytoplankton in the pond provide natural feed and good environmental condition for shrimp cultivation.

Spirulina platensis is a filamentous cyanobacterium that has been commerically used for fish feed and human food supplement. Low-cost production of Spirulina is needed when considering large-scale culture especially for industrial purposes. The aim of this study was to explain the effect of calcium nitrate (Ca(NO3)2) on growth, biomass, pigment, and protein production of S. platensis and to determine the best calcium nitrate concentration for Spirulina production.The microalgae was cultured at four calcium nitrate concentrations (1, 1.5, 2.0 and 2.5 g/L) with salinity of 15 ppt, constant light intensity of 4,000 lux and photoperiod of 24:0 light:dark cycles for 4 days. The results showed that different calcium nitrate concentrations remarkably affected the growth, biomass production, pigment and protein content of S. platensis (p<0.05). The highest specific growth rate of 0.721 day-1 and biomass concentration of 1.512 g/Lwere achieved at calcium nitrate concentration of 2.5 g/L. Moreover, the algae had the highest chlorophyll-a, carotenoid and protein content at 2.5 g L-1. Increasing calcium nitrate concentration from 1 to 2.5 g/L led to an increase in biomass, pigment and protein production of S. platensis. However, there was no significant difference between 2 and 2.5 g L-1 calcium nitrate concentrations. We suggest that 2-2.5 g/L Ca(NO3)2 concentration can be used profitably for S. platensis production.

Abstract. Fakhri M, Riyani E, Ekawati AW, Arifin NB, Yuniarti A, Widyawati Y, Saputra IK, Samuel PD, Arif MZ, Hariati AM. 2021. Biomass, pigment production, and nutrient uptake of Chlorella sp. under different photoperiods. Biodiversitas 22: 5344-5349. Chlorella sp. is well-known as a functional feed in fish culture and has been utilized in the food industry. In phototrophic cultivation, photoperiod plays a fundamental part in the growth and pigment content of microalgae. This work was purposed to evaluate the effect of light:dark cycle on the growth rate, production of biomass and pigment and nutrient utilization of Chlorella sp. Four photoperiods (8:16, 12:12, 18:6, and 24:0 h light:dark regimes) under a constant light intensity of 4500 lux were applied in this study. The results demonstrated that increasing light duration led to increased cell growth, biomass, and pigment production of Chlorella sp. The best cell concentration, specific growth rate, and biomass production were 28.5 x 106 cells mL-1, 1.47 day-1, and 0.815 g L-1 dry weight, respectively, under continuous illumination. The maximum chlorophyll a of 19.205 mg L-1 and carotenoid of 4.656 mg L-1 were obtained at 24:0 h photoperiod. The highest uptake of nitrate (66.331%) and phosphate (76.191%) by Chlorella sp. were achieved under 24 h light regime. Improving the uptake of nutrients resulted in enhanced growth and pigment content of Chlorella sp. We conclude that continuous illumination is the best photoperiod to produce biomass and pigment and improve the nutrient removal of Chlorella sp.

Edwardsiellosis adalah penyakit yang biasa menginfeksi ikan air tawar termasuk ikan lele (Clarias sp). Penyakit Edwardsiellosis disebabkan oleh infeksi bakteri Edwardsiella tarda dan dapat menyebabkan kematian masal pada ikan air tawar yang dibudidayakan. Penanggulangan penyakit pada ikan air tawar dapat menggunakan obat-obatan atau antibiotik yang tergolong aman dan penggunaannya sesuai aturan pemerintah. Penelitian ini bertujuan untuk mengetahui dosis oxytetracycline yang tepat sebagai obat ikan lele (Clarias sp.) yang terinfeksi bakteri Edwardsiella tarda melalui analisa histologi. Desain penelitian menggunakan Rancangan Acak Lengkap (RAL) dengan 3 perlakuan, 1 kontrol dan 3 kali ulangan pada tiap perlakuan. Ikan lele yang digunakan berukuran ± 25 cm dan dosis oxytetracycline yang digunakan yaitu 15, 30, dan 45 ppm. Hasil menunjukkan adanya kerusakan jaringan Nekrosis, Kongesti, Degenerasi Hialin, dan Deskuamasi Epitel Integumen pada ikan yang terinfeksi bakteri Edwardsiella tarda dengan scoring kerusakan terendah pada ikan yang diobati oxytetracycline dengan dosis 45 ppm. Hal ini mengindikasikan bahwa pemberian oxytetracycline berpengaruh terhadap histologi otot dan pemulihan kesehatan ikan.