Judul: Asosiasi ikan dengan padang lamun di perairan karang lebar, kepulauan seribu, Jakarta
Abstrak: Seagrass is a complex aquatic ecosystem in trophics area with high productivity and biodiversity. This ecosystem play role of physics, chemistry, and biology. Biologically, seagrass used as spawning, feeding, and nursery ground for aquatic biota, especially fish. Seagrass is part of the coastal region where there are many human activities, such as coastal development, overfishing, boat traffic, and sand mining. One of the seagrass areas with high human activity around is Karang Lebar shallow waters, Kepulauan Seribu, Jakarta. Types of data taken in this research is primary data, including environmental parameters, condition of seagrass and fishes that live in it. Fishes caught by gill net with mesh size from 0.5 – 3 cm. Sampling conducted in day and night, started from March until May 2011 with the arrest period twice a month. Observations were made at three stations of seagrass beds with different covering conditions (healthy, less healthy, and poor). Sorensen similarity index, constancy index, and fidelity index were used to determine the relationship of fish associated with seagrasses. In addition, it also used statistical tests such as Pearson correlation, biplot analysis, and Two Way ANOVA as a tool to test the truth of descriptive analysis results based on the facts as represented by data. Three seagrass species found in the observation area include Thalassia hemprichii, Cymodocea rotundata, and Halophila ovalis. The highest cover obtained from Cymodocea rotundata. Value of total cover ranged between 26.5 % - 82.13 %. The highest INP of the species obtained from Cymodocea rotundata, indicate that these organisms have a great influence to the ecosystem. Fish were caught consist of 37 species and 22 genera. Total abundance was found in all three observation stations for 2287 individuals (healthy seagrass), 547 individuals (less healthy seagrass), and 889 individuals (poor seagrass). Pre-adult fish dominate at each station. While the most commonly species found are Hypoatherina temmincki, Gerres oyena, and Scolopsis lineatus. The catch composition on day and night differ in terms of abundance, type and size of the species. Adult fish were more common at night, although abundance in day were more than in the night. Based on size and species composition, healthy seagrass and less healthy seagrass functioning as nursery ground and feeding ground, while poor seagrass tend to play a role as feeding ground, especially for carnivorous fish. Change of the diversity and dominance value in the day and night allegedly due to the activity or movement of fish, which is not a permanent resident in seagrass. Referring Tomascik et al. (1997), permanent resident fish found in the observation area is Apogon margaritiphorus. Based on Sorensen similarity index, the fishes were divided into six groups of species. Constancy index ranging from 0-1, while fidelity index ranges from 0-3. Group of species 1 has a high preference on healthy and poor seagrasses, and low preference in unhealthy seagrasses. Healthy seagrass also preferred by group 6, which include Apogon kallopterus, Apogon margaritiphorus, Hemirhapus far, Chrysiptera hemicyanea, and Syngnathoides biaculeatus. Groups of species that have a high preference towards less healthy habitat is group 4, with Stethojulis balteata, and Chaetodon
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Judul: Food and Trophic Guild of Fish Assemblages in the  Seagrass Ecosystem of Panggang Island, Kepulauan Seribu
Abstrak: Pulau Panggang dengan jumlah penduduk terbanyak di Taman Nasional Kepulauan Seribu memiliki ekosistem lamun. Ekosistem lamun berperan penting bagi kehidupan ikan yaitu sebagai daerah asuhan dan tempat mencari makan kumpulan ikan. Penelitian ini bertujuan untuk menentukan peran fungsional komunitas ikan yang berasosiasi dengan padang lamun secara temporal (siang dan malam) di perairan Pulau Panggang, Kepulauan Seribu. Pengambilan sampel ikan dengan pukat tarik dilakukan pada siang dan malam hari selama lima bulan yaitu April, Mei, Juli, Agustus, dan September 2018. Analisis data yang digunakan meliputi indeks bagian terbesar, tingkat trofik, dan strategi pola makan ikan. Sebanyak 74 spesies ikan dari 55 genera dan 30 famili ditemukan selama penelitian. Sebagian besar ikan yang tertangkap berada pada stadia yuwana dengan status kepenghunian pengunjung sesekali. Makanan dominan yang dikonsumsi ikan yang berasosiasi dengan padang lamun pada siang dan malam hari berturut-turut adalah krustasea dan zooplankton. Peran fungsional kumpulan ikan di padang lamun Pulau Panggang pada siang dan malam hari terdiri atas tujuh serikat trofik yaitu detritivora, fitoplanktivora, algivora, zooplanktivora, zoobentivora, krustasivora, dan piscivora dengan nilai tingkat trofik berkisar antara 2,00 sampai dengan 4,50. Secara keseluruhan, ikan yang berasosiasi dengan lamun melakukan strategi pola makan generalis-spesialis. Studi ini menegaskan bahwa sebagian besar spesies ikan laut menggunakan padang lamun di perairan Pulau Panggang sebagai daerah asuhan dan mencari makan., Panggang Island with the largest population in the Kepulauan Seribu Nasional Park has a seagrass ecosystem. Seagrass ecosystem plays an important role as a nursery and feeding grounds for fish assemblages. The purpose of the study was to determine the functional part of the seagrass-associated fish community temporally (day and night) in the waters of Panggang Island, Kepulauan Seribu. Fish sampling with seine net was conducted day and night for five months, namely April, May, July, August, and September 2018. Data analysis includes an index of preponderance, trophic level, and fish diet strategy. A total of 74 fish species from 55 genera and 30 families was collected. Most of them were fish juveniles with the residential status as occasional visitors. The dominant food items consumed by seagrass-associated fish during day and night were crustaceans and zooplankton, respectively. The functional role of fish assemblages during the day and night consists of seven trophic guilds: detritivores, phytoplanktivores, algivores, zooplanktivores zoobentivores, crustacivores, and piscivores with trophic level values ranging from 2.00 to 4.50. Overall, seagrass-associated fish performed a generalist-specialist feeding strategy. This study confirms that most marine fish species use the seagrass beds on Panggang Island as nurseries and feeding grounds.
Keyword: fish assemblages, juvenile, Panggang Island, seagrass bed, trophic guild

Judul: Konstruksi aritmetika kurva eliptik F(2m) supersingular dan non-supersingular untuk skema kunci publik ElGamal
Abstrak: Algoritme ElGamal adalah salah satu algoritme kunci publik dengan aritmetik modular p yang mempunyai struktur grip siklik Z(p). Tingkat keanaman algoritme ini terletak pada pemecahan masalah logaritme diskret dari Z(p). Akan tetapi, tingkat keamanan tadi tahun ke tahun semakin menurun yang disebabkan kemampuan pemecahan algoritme diskret semakin meningkat. Untuk memenuhi tingkat keamanan yang memadai dibutuhkan p yang cukup besar yang menyebabkan proses enkripsi dan dekripsi menjadi lambat.
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