The purpose of this study was to determine the effect of different densities on Survival Rate (SR) spat pearl shells (Pinctada maxima) and the right density on the maintenance container in the sea. The method used is Completely Randomized Design (CRD) which consists of 6 treatments and 3 replications, namely treatment 1 (control) 60 ind / pocket; treatment 2 (93 ind / pocket); treatment 3 (126 ind / pocket); treatment 4 (159 ind / pocket); treatment 5 (192 ind / pocket); and treatment 6 (225 ind / pocket). Spat size used is 0.8-1.7 cm (45 days) in pocket net (47 x 60 cm). The results of the study for 45 days showed the highest SR percentage calculation (100%) owned by 225 ind / pocket (P6) density and 93 ind / pocket (P2) density. The lowest SR value is at P1 with 60 ind / pocket density and followed by other treatments such as P3, P4 and P5. However, the average growth rate of spat shell at 192 ind / pocket (P5) density tends to be faster with a value of 1.71 cm compared to 60 ind / pocket (P1) density which has the lowest value of 1.43 cm. Weight growth with the highest value in P4 (159 ind / pocket) with a value of 1, 30 gr and the lowest value of 1.00 gr was at P5 (192 ind / pocket). Based on the results of the study it was concluded that different stocking densities did not significantly (P> 0.05) the SR spat maintained for 45 days and the best stocking density for SR was obtained in treatment 2 (93 ind / pocket) and treatment 6 (225 ind / pocket).

Plankton has an important role for aquatic ecosystems, especially in the food network in a waters. This study aims to assess the abundance and diversity index of plankton in Sire Beach, North Lombok Regency. The study was conducted in September 2019 using purposive sampling with 9 sample points. The water sample was filtered using plankton net then put into the sample bottle for identification in the laboratory. Shannon-Wienner Index was used for determining diversity of plankton species. The types of plankton found were 12 genera of phytoplankton from the Bacillariophyta group, including: Biddulphia, Coscinodiscus, Cocconeis, Cylindrotheca, Diploneis, Fragilaria, Gyrosigma, Licmophora, Navicula, Nitzschia, Pleurosigma, and Triceratium. The highest abundance of phytoplankton belonged to Coscinodiscus species as many as 1.380 cells/l at station 2.3. The high abundance of Coscinodiscus might be due to a nutrient supply in these waters. Seagrass ecosystem was thought to have an important role in obtaining nutrients for phytoplankton. Diversity index has a value which ranges between 1.117505-1.841236 showing that it is in the medium category. The uniformity index ranges from 0.450718-0.673373 indicating that the distribution of plankton species in each station is even. The dominance index ranges from 0.233508-0.522215. This shows that there is no type of plankton that dominates the waters of Sire Beach. This is due to the abundance of plankton species at each station which is fairly evenly distributed.

Abstrak : Penelitian kepadatan spat kerang mutiara yang dipelihara di alam perlu terus dilakukan karena belum ada patokan tingkat kepadatan yang sesuai untuk usaha komersial. Oleh karena itu dilakukan penelitian dengan tujuan mengetahui pengaruh kepadatan terhadap pertumbuhan dan tingkat kelangsungan hidup spat kerang mutiara (Pinctada maxima).  Metode yang digunakan adalah Rancangan Acak Kelompok (RAK) terdiri dari 5 perlakuan dan 3 ulangan, yakni perlakuan A (60 ind/poket), B (75 ind/poket), C (90 ind/poket), D (105 ind/poket), dan perlakuan E (120 ind/poket). Ukuran spat yang digunakan rata-rata 1 cm pada poket (keranjang pemeliharaan) 45x60 cm2. Hasil penelitian selama 45 hari menunjukan bahwa pertumbuhan pada semua perlakuan tidak berbeda nyata, namun pertumbuhan terbaik dengan nilai 0,70 cm untuk pertumbuhan mutlak dan 0,69% untuk laju pertumbuhan harian dimiliki oleh kepadatan yang rendah yakni 60 ind/poket, disusul oleh perlakuan lainnya seperti perlakuan B,C,D, dan E. Hasil uji ANOVA, SR didapatkan hasil persentase yang berbeda nyata, yakni terdapat pada perlakuan A (60 ind/poket) dengan nilai SR 90,44% dan pada perlakuan E (120 ind/poket) dengan nilai SR 74,44%. Berdasarkan hasil penelitian, disimpulkan bahwa padat penebaran yang berbeda tidak berpengaruh nyata terhadap pertumbuhan spat kerang mutiara, namun berpengaruh nyata terhadap tingkat kelangsungan hidup (SR) spat kerang mutiara (Pinctada maxima) yang dipelihara selama 45 hari.Kata kunci : Pertumbuhan, kelangsungan hidup, spat, Pinctada maximaAbstract : The study of pearl shell spat density maintained in nature needs to be continued because there is no standard level of density suitable for commercial businesses. Therefore a study was conducted with the aim of knowing the effect of density on growth and survival rate of pearl oyster spat (Pinctada maxima). The method used is Randomized Block Design (RBD) consisting of 5 treatments and 3 replications, namely treatment A (60 ind / pocket), B (75 ind / pocket), C (90 ind / pocket), D (105 ind / pocket) ), and treatment E (120 ind / pocket). The size of the spat used was 1 cm on the pocket (maintenance basket) 45x60 cm2. The results of the 45-day study showed that growth in all treatments was not significantly different, but the best growth was 0.70 cm for absolute growth and 0.69% for the daily growth rate owned by a low density of 60 ind / pocket, followed by treatment others such as treatment B, C, D, and E. The results of the SR ANOVA test showed that the percentage results were significantly different, which were found in treatment A (60 ind / pocket) with SR values of 90.44% and in treatment E (120 ind / pocket) with an SR of 74.44%. Based on the results of the study, it was concluded that the different stocking densities had no significant effect on the growth of pearl shell spat, but significantly affected the survival rate (SR) of pearl shell spat (Pinctada maxima) which was maintained for 45 days.Keywords: growth, survival rate, spat, Pinctada maxima.

Salah satu kecamatan dengan produksi udang terbesar saat ini di Kabupaten Sumbawa adalah kecamatan labangka. Mengingat akan dikembangnya kegiatan tambak budidaya udang secara ekstensif di Kecamatan tersebut, maka perlu diketahui kondisi existing dari perairan laut di wilayah ini. Hal ini dibutuhkan sebagai bahan pertimbangan dalam pengelolaan tambak budidaya udang agar produksi udang serta kualitas perairan dapat terjaga. Salah satu indicator perubahan lingkungan perairan yang dapat diamati yaitu fitoplankton. Oleh karena itu, penelitian ini bertujuan untuk mengetahui kelimpahan fitoplankton dan parameter kualitas air lainnya di perairan laut Labangka sehingga dapat diketahui kondisi awal dari perairan laut Labangka sebelum dimulainya kegiatan pengembangan tambak udang di kawasan ini. Sampling plankton maupun air laut menggunakan purposive sampling. Analisis data Fitoplankton meliputi penghitungan kelimpahan (D), indeks diversitas (H’), indeks keseragaman E, dan indeks dominansi (D). Sedangkan parameter kualitas air yang diukur yaitu pH, total ammoniak, fosfat, nitrat, nitrit, dan BOT. Hasil perhitungan kelimpahan fitoplankton dan hasil pengukuran parameter kualitas air selanjutnya dianalisis secara statistik menggunakan korelasi Pearson untuk melihat hubungan antar variable yang diukur. Hasil pengamatan sampel fitoplankton menunjukkan bahwa terdapat 11 genera yaitu Coscinodiscus, Biddulphia, Nitzschia, Rhizosolenia, Pleurosigma, Triceratium, Ceratium, Pelagothrix, Trichodesmium, Dinophysis, dan Thallasionema. Selain itu, diketahui bahwa perairan ini masih dapat dikatakan aman karena kelimpahan fitoplankton terhitung kurang dari 15.000 ind/L. Sementara itu, nilai pH, total ammoniak, fosfat, nitrat, nitrit, dan BOT masih dalam kisaran aman walaupun ada parameter yang memiliki nilai melebihi baku mutu. Dapat disimpulkan bahwa perairan Labangka memiliki kualitas perairan yang baik dan sesuai untuk pengembangan kegiatan budidaya.

This research aimed to address the effect of seaweed Kappaphycus alvarezii (result of tissue culture) planting depth on the seaweed growth. This reasearch was conducted in Seriwe Village water, Jerowaru subdistrict, East Lombok Regency known as the largest minapolitan area in West Nusa Tenggara Province. Method used in this research was completely randomized design consisting of five treatments of planting depth which were 0.15 m, 0.5 m, 1 m, 1.5 m, and 2 m. Each treatment was repeated four times. Main parameters measured were the seaweed Daily Growth Rate, Absolute Growth. In addition, water quality parameters measured were temperature, light intensity, dissolved oxygen, salinity, pH, Phosphate, ammoniac, TAN, TDS, and current speed. Data collected were analyzed using ANOVA with significant level of 5% and any significant difference between the treatments was analyzed using LSD in the same significant level. The result of data analysis shows that the most optimum planting depth appropriate for K. alvarezii growth is 0.5 m.