Judul: Profile of water Quality at Different Depths in  the Thousand Island on the Productivity of Growing Lobsters with Submersible Net Cage System
Abstrak: Budidaya perikanan laut di Indonesia terus mengalami perkembangan seiring tingginya permintaan pasar dalam negeri maupun luar negeri. Salah satu komoditas utama hasil perikanan laut yang memiliki eksistensi tinggi terhadap permintaan pasar luar negeri adalah lobster pasir. Penelitian ini bertujuan untuk menganalisis parameter kualitas air, kelimpahan plankton, dan bakteri terhadap pertumbuhan pada budidaya lobster sistem karamba jaring tenggelam. Pengukuran parameter lingkungan dilakukan sebanyak empat kali, dan bobot sebanyak dua kali pada dua kedalaman berbeda (3 m dan 5 m). Hasil penelitian didapatkan bahwa kondisi lingkungan perairan di dua kedalaman bernilai optimum untuk pemeliharaan lobster. Keberadaan mikroorganisme berupa fitoplankton banyak ditemukan pada kedalaman 3 m sebesar 402.957 sel/m3 , sedangkan zooplankton banyak ditemukan pada kedalaman 5 m sebesar 15.030 ind/m3 . Keberadaan bakteri di perairan banyak ditemukan pada kedalaman 5 m sebesar 312 × 107 CFU mL-1 . Kinerja pertumbuhan bobot lobster terbaik terdapat pada perlakuan 80 g di kedalaman 5 m sebesar 39,64±9,01 g. Oleh karena itu, disimpulkan bahwa profil perairan di kepulauan seribu bernilai optimum, dan kedalaman 5 m menghasilkan pertumbuhan terbaik pada pembesaran lobster di karamba jaring tenggelam., Marine aquaculture in Indonesia continues to develop in line with the high demand for domestic and foreign markets. One of the main commodities of marine fishery products that has a high existence against foreign market demand is sand lobster. This study aims to analyze the parameters of water quality, an abundance of plankton, and bacteria on the growth of lobster culture in the Sinking Net Cage system. Measurement of environmental parameters was carried out four times, and weights twice at two different depths (3 and 5 m). Data were analyzed using ANOVA test and continued with Tukey's test. The results showed that the environmental conditions of the waters at two depths were of optimum value for lobster rearing. The presence of microorganisms for lobster in the form of phytoplankton was found at a depth of 3 m at 402.957 cells/m3 , while zooplankton was found at a depth of 5 m at 15.030 ind/m3 . The presence of bacteria in the waters was found at a depth of 5 m at 312 × 107 CFU mL-1 . The best lobster weight growth performance was found in the treatment of 80 g at a depth of 5 m of 39.64±9.01 g. Therefore, it was concluded that the water profile in the Thousand Islands was of optimum value, and a depth of 5 m resulted in the best growth of lobster rearing in the submersible cage.
Keyword: cages, depth, growth, lobsters

Judul: Production Performance of Spiny Lobster  Panulirus homarus Grow-out at in Submersible Net Cage with Different Depths
Abstrak: Suhu, intensitas cahaya, gelombang, kekeruhan, arus, dan tekanan dipengaruhi oleh kedalaman perairan. Kinerja produksi lobster pasir akan maksimal apabila diiringi dengan penyesuaian lingkungan budidaya dengan habitat alaminya. Tujuan penelitian ini adalah menentukan kedalaman optimal bagi kehidupan lobster untuk meningkatkan kinerja produksi dan keuntungan di Karamba Jaring Tenggelam. Penelitian ini menggunakan Rancangan Acak Lengkap dengan tiga kedalaman berbeda, yaitu 1 m, 2 m, dan 3 m di bawah permukaan air laut dengan tiga kali ulangan. Sebanyak 72 ekor lobster dipelihara di dalam karamba berukuran (1 x 1 x 1) m dengan kepadatan 8 ekor/m2 dan bobot rata-rata 80,14+0,33 g selama 40 hari. Pemberian pakan dilakukan sebanyak 2 kali sehari dengan bobot 5% dari biomassa lobster. Parameter uji pada penelitian ini meliputi kinerja produksi, kualitas air, dan analisis usaha. Data dianalisis menggunakan ANOVA pada selang kepercayaan 95%. Hasil penelitian menunjukkan tingkat kedalaman yang optimal pada penelitian ini untuk meningkatkan kinerja produksi pada pembesaran lobster pasir di karamba jaring tenggelam adalah kedalaman 2 m. Pada kedalaman tersebut, lobster memiliki hasil kinerja produksi terbaik, yang ditunjukkan dengan nilai produktivitas yang paling tinggi. Sedangkan kedalaman 3 m memiliki R/C rasio tertinggi dan PP yang lebih singkat dalam usaha budidaya lobster pasir pada sistem Karamba Jaring Tenggelam., Temperature, light intensity, waves, turbidity, currents, and pressure are affected by water depth. The performance of spiny lobster production will be maximized if it is accompanied by adjustment of the cultivation environment to its natural habitat. The purpose of this study was to determine the optimal depth for lobster life to increase production performance and profitability in the Submersible Net Cages. This study used a completely randomized design with three depths, namely 1 m, 2 m, and 3 m below sea level, with three replications. A total of 72 lobsters were kept in cages measuring 1 m x 1 m x 1 m with a density of 8 fish/m2 and an average weight of 80.14±0.33 g for 40 days. Feeding was carried out 2 times a day with a weight of 5% of the lobster biomass. The test parameters in this study include production performance, water quality, and business analysis. Data were analyzed using ANOVA at 95% confidence interval. The results showed that the optimal level of depth in this study to improve production performance on rearing spiny lobster in Submersible Net Cages was 2 m. At this depth, lobster has the best production performance, indicated by the highest production value. At the same time, the depth of 3 m has the highest R/C ratio and shorter PP in spiny lobster cultivation in the Submersible Net Cage system.
Keyword: cages, depth, production performance, spiny lobster

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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