Judul: Isolated Populations of Nitrifying and Denitrifying Bacteria in Seagrass Ecosystems on Pramuka Island, Jakarta
Abstrak: Bakteri mengambil peran penting pada ekosistem lamun, salah satu contohnya peran bakteri nitrifikasi dan denitrifikasi yang berperan dalam siklus nitrogen pada ekosistem lamun. Nitrogen adalah nutrien esensial yang sangat dibutuhkan oleh tanaman dan organisme hidup lainnya. Tujuan penelitian ini untuk mengisolasi bakteri asosiasi sedimen lamun yang berperan dalam siklus nitrifikasi dan denitrifikasi di ekosistem lamun Pulau Pramuka, Kepulauan Seribu, Jakarta. Penelitian yang dilakukan meliputi isolasi bakteri menggunakan media spesifik nitrifikasi dan denitrifikasi dari sampel sedimen lamun, karakterisasi bakteri secara morfologi koloni, bentuk sel dan pewarnaan Gram, uji oksidatif/fermentatif, katalase, oksidase, selulase, motilitas, serta dilakukan pengukuran kualitas perairan, kualitas sedimen, dan komposisi lamun. Jenis lamun yang ditemukan pada lokasi pengamatan yaitu, Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, dan Enhalus acoroides. Jenis lamun Thalassia hemprichii mendominasi pada kedua Stasiun penelitian. Isolat bakteri yang berhasil diisolasi menggunakan media spesifik nitrifikasi berjumlah 16 isolat dan isolat bakteri yang berhasil diisolasi menggunakan media denitrifikasi berjumlah 23 isolat. Karakteristik isolat bakteri pada kedua Stasiun penelitian didominasi tepian licin, bentuk bundar, elevasi cembung, pigmen putih, dan dominan masuk kedalam golongan Gram negatif dengan bentuk basil. Uji oksidatif mendapatkan hasil 8 isolat oksidatif, oksidase positif ditemukan pada 29 isolat, pengujian katalase ditemukan 39 isolat positif, dan uji motilitas positif pada bakteri jenis nitrifikasi dan negatif pada bakteri jenis denitrifikasi. Hasil dari uji terhadap seluruh isolat selanjutnya dilakukan identifikasi dan memperoleh hasil 5 genus bakteri yaitu, Pseudomonas, Corynebacterium, Achromobacter, Moraxella, dan Brucella. Jumlah isolat bakteri yang terisolasi dikaitkan dengan kerapatan lamun perjenis dengan menggunakan analisis Pearson Correlation yang menunjukkan hasil adanya hubungan isolat bakteri terhadap kerapatan jenis lamun, Bacteria play an important role in seagrass ecosystems, one example being the role of nitrifying and denitrifying bacteria in the nitrogen cycle of seagrass ecosystems. Nitrogen is an essential nutrien required by plants and other living organisms. The objective of this research is to isolate sediment-associated bacteria that play a role in the nitrification and denitrification cycles in the seagrass ecosystem of Pramuka Island, Thousand Islands, Jakarta. The research includes isolating bacteria using specific nitrification and denitrification media from seagrass sediment samples, characterizing bacteria based on colony morphology, cell shape and Gram staining, oxidative/fermentative tests, catalase, oxidase, cellulase, motility, as well as measuring water quality, sediment quality, and seagrass composition. The seagrass species found at the observation site are Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, and Enhalus acoroides. Thalassia hemprichii dominates at both research stations. A total of 16 bacterial isolates were successfully isolated using specific nitrification media, and 23 bacterial isolates were successfully isolated using denitrification media. The characteristics of the bacterial isolates at both research stations are predominantly smooth edges, round shape, convex elevation, white pigment, and predominantly fall into the Gram-negative group with bacillus shape. The oxidative test resulted in 8 oxidative isolates, positive oxidase was found in 29 isolates, catalase testing showed 39 positive isolates, and motility test was positive for nitrifying bacteria and negative for denitrifying bacteria. Further identification of all isolates resulted in the discovery of 5 bacterial genera: Pseudomonas, Corynebacterium, Achromobacter, Moraxella, and Brucella. The number of isolated bacteria is associated with the density of seagrass
Keyword: bacteria, denitrification, nitrification, seagrass, sediment

Judul: Potensi Isolat Bakteri Simbion Spons Agelas conifera di Ekosistem Lamun Pulau Pramuka, Kepulauan Seribu, Jakarta
Abstrak: Pulau Pramuka merupakan pulau dengan banyak ekosistem, salah satunya adalah ekosistem lamun. Ekosistem lamun memiliki peranan sebagai habitat oleh banyak biota, salah satunya adalah spons. Spons Agelas conifera adalah jenis spons yang paling dominan ditemukan di Pulau Pramuka, Kepulauan Seribu. Kemampuan spons untuk memproduksi senyawa metabolit sekunder sangat dipengaruhi oleh kondisi habitat spons. Tingginya tingkat kesuburan ekosistem lamun dapat mempengaruhi produksi metabolit sekunder spons. Penelitian ini bertujuan mengisolasi dan menguji potensi bakteri simbion spons serta mengetahui jenis lamun yang berasosiasi dengan Agelas conifera. Isolasi bakteri simbion spons dilakukan mengunakan media Zobell 2216 ½ strength. Uji yang dilakukan adalah antibakteri, antifungi, selulase, kitinase, resistensi sinar UV, toleransi suhu, serta pengukuran kualitas perairan dan kualitas sedimen. Jenis lamun yang ditemukan pada lokasi pengamatan yaitu, Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, dan Enhalus acoroides. Thalassia hemprichii mendominasi di kedua Stasiun penelitian. Sebanyak 61 individu spons Agelas conifera ditemukan pada penelitian ini. Spons Agelas conifera lebih banyak ditemukan pada kerapatan dan tutupan lamun yang tinggi, yaitu jenis Thalassia hemprichii. Isolat bakteri ditemukan sebanyak 45 isolat yang bersimbiosis dengan spons. Jumlah spons yang ditemukan dikaitkan dengan persentase tutupan lamun perjenis dengan menggunakan analisis koresponden yang menunjukkan spons lebih banyak ditemukan pada tutupan lamun T.hemprichii. Potensi bakteri simbion yang ditemukan bervariasi seperti resisten terhadap sinar ultraviolet (UV) dan rentang toleransi suhu yang lebar. Hasil yang berbeda nyata antara potensi pada kedua stasiun ditunjukkan oleh uji ANOVA single factor dengan p<0.05. Dibutuhkan pengujian lebih lanjut untuk melihat potensi lebih dalam dari bakteri simbion spons Agelas conifera di ekosistem lamun Pulau Pramuka Kepulauan Seribu., Pramuka Island is an island with many ecosystems, one of which is a seagrass ecosystem. The seagrass ecosystem has a role as a habitat for many biota, one of which is a sponge. Agelas conifera sponge is the most dominant sponge found in Pramuka Island, Kepulauan Seribu. The ability of sponges to produce secondary metabolites is greatly influenced by the conditions of the sponge's habitat. The high fertility rate of the seagrass ecosystem can affect the production of secondary metabolites of the sponge. This study aims to isolate and test the potential of sponge symbiont bacteria and to determine the types of seagrass associated with Agelas conifera. Spongy symbiont bacteria was isolated using Zobell 2216 ½ strength media. The tests carried out were antibacterial, anti-fungal, cellulase, chitinase, UV resistance, temperature tolerance, and measurement of water quality and sediment quality. The types of seagrass found at the observation site were Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, and Enhalus acoroides. Thalassia hemprichii dominates at both research stations. A total of 61 individual Agelas conifera sponges were found in this study. Agelas conifera sponges are more commonly found in high density and cover of seagrass, namely Thalassia hemprichii. As many as 45 isolates were found in symbiosis with a sponge. The number of sponges found was associated with the percentage of seagrass cover per type using a correspondent analysis which showed that sponges were more common in T.hemprichii seagrass cover. The potential of symbiont bacteria found varied such as resistance to ultraviolet (UV) rays and a wide temperature tolerance
Keyword: Agelas conifera, Pramuka Island, Seagrass habitat, Symbiotic bacteria

Judul: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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