Judul: Dinamika Komunitas Plankton di Kolam Pendederan Ikan Tengadak (Barbonymus schwanenfeldii)
Abstrak: Plankton both phytoplankton and zooplankton is one of essential factor to establishing the success of aquaculture. Artificial feeding in aquaculture may affects the condition of plankton. The plankton can give positive or negative impact to the survival of fish like Tengadak (Barbonymus schwanenfeldii). Plankton observations are expected to provide information about the dynamics of plankton during the fish maintenance. The results of this study indicate that the phytoplankton was dominated by class of Chlorophyceae and the zooplankton was dominated by Rotifera. The value of diversity index tend to moderate, with the value of eveness index tend to high and value of dominance index tend to low for both phytoplankton and zooplankton. Statistical test results by SPSS program showed that the effect of feeding treatment did not affect the composition and abundance of plankton class. In this study, harmful plankton was not found, and was not affected the survival of Tengadak (B. schwanenfeldii).
Keyword: Tengadak (Barbonymus schwanenfeldiii), Plankton, Artificial feed

Judul: Plankton Community Structure in Intensive Pond
Abstrak: Tambak merupakan suatu ekosistem perairan tertutup yang memiliki kondisi lingkungan berubah-ubah. Manajemen kualitas air menjadi hal yang penting untuk dilakukan karena berdampak pada komunitas plankton. Penelitian ini bertujuan untuk menganalisis kondisi struktur komunitas plankton di tambak udang yang dikelola secara intensif. Penelitian dilakukan di Tambak Sarjo, Sulawesi Barat dan di Laboratorium Biologi Mikro 1, Institut Pertanian Bogor. Data yang digunakan yaitu data primer (sampel plankton) dan sekunder (data kualitas air). Pengambilan sampel plankton dilakukan pada dua petak tambak berdasarkan kesamaan umur awal tebar dari benih udang selama tiga bulan. Data kualitas air diperoleh dari laboran tambak Sarjo. Analisis data yang digunakan adalah indeks diversitas meliputi indeks keanekaragaman, keseragaman, dan dominansi serta analisis komponen utama dan regresi linier berganda. Komunitas plankton yang ditemukan terdiri dari lima jenis fitoplankton dan empat jenis zooplankton dengan total 14 genus fitoplankton dan 9 genus zooplankton. Kelimpahan plankton yang ditemukan berfluktuasi. Kelas Dinophyceae dan Protozoa hampir ditemukan pada setiap kelompok waktu pengamatan. Struktur komunitas plankton selama pengamatan memiliki keanekaragaman rendah, keseragaman rendah hingga sedang, dan dominansi yang cenderung rendah hingga sedang untuk fitoplankton dan rendah dengan kecenderungan tinggi untuk zooplankton. Perubahan kelimpahan plankton berkorelasi kuat dengan parameter kualitas air yang ada., Ponds are closed aquatic ecosystems that have changing environmental conditions. Water quality management is an important thing to do because it impacts the plankton community. This research aims to analyze the condition of plankton community structure in intensively managed shrimp ponds. The research was conducted in Tambak Sarjo, West Sulawesi, and at Micro Biology Laboratory 1, Bogor Agricultural Institute. The data used are primary (plankton samples) and secondary (water quality data). Plankton sampling was carried out in two pond plots based on the similarity in the initial stocking age of the shrimp seeds for three months. Water quality data was obtained from the Sarjo Pond laboratory. The data analysis used is a diversity index including indices of diversity, evennes, and dominance, principal component analysis, and multiple linear regression. The plankton community consisted of five types of phytoplankton and four types of zooplankton with 14 phytoplankton genera and 9 zooplankton genera. The abundance of plankton found fluctuates. The Dinophyceae and Protozoa classes were almost found in every observation time group. The plankton community structure during observations had low diversity, low to moderate uniformity, and dominance that tended to be low to moderate for phytoplankton and low with a tendency to be high for zooplankton. Changes in plankton abundance are strongly correlated with existing water quality parameters.
Keyword: phytoplankton, ponds, water quality, zooplankton

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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