Judul: Analysis of Periphyton Presence Related to Physical Chemical Parameter and the Characteristic of Seagrass beds in Pari Island
Abstrak: Seagrasses represent one of the important and highly productive ecosystems of the world, which provides critical habitat for many animals and plants including periphyton. The characteristics of seagrass beds are acutely responsive to density and distribution of assosiated periphyton due to physical chemical factors and community structure of the seagrass itself. The aims of this research were to investigate composition and density of periphyton taxa between mixed vegetation and monospesific seagrasses beds and to study the physics chemical parameters that influence the community structure of periphyton on seagrass leaves and the density of seagrass community. The results showed that the highest density of seagrasses and periphyton occured in station II with mixed vegetation and consists of four species of seagrasses. PCA analysis indicated that the most influenced of physical chemical factors were current, nitrate and phosphate, while the presence and density of periphyton weree affected by seagrass densities.
Keyword: physical chemical factors, periphyton, characteristic of seagrass bed.

Judul: Keterkaitan padang lamun sebagai pemerangkap dan penghasil bahan organik dengan struktur komunitas makrozoobentos di perairan pulau Barrang Lompo
Abstrak: Seagrass beds is one of ecosystem in coastal waters which is known for its high organic productivity. The productivity derives from litter fall, epiphyte, phytoplankton and suspended particles which trapped among seagrass. Organic material then undergoing a process of decomposition and becomes a source of nutrients. Furthermore, the nutrients will be used by seagrass itself and other aquatic organisms. Macrozoobenthos is a part of the organisms that served as a connector in material cycles and energy flow, from high-level producers to consumers in the waters. The presence of macrozoobenthos in seagrass bed, will enable to support higher fish production in coastal areas. From this starting point, these studies were conducted to analyze the connection between seagrass beds as a producer and organic matter traps and its influenced to macrozoobenthos community structure. The aim of this study is to know the effect of seagrass density toward the total organic material on the bottom substrate, to investigate the effect of seagrass density on the abundance of macrozoobenthos and to determine the influence of total organic material against macrozoobenthos abundance, as well as the rate of deposition of suspended particles (mg/cm2/day). Sampling were taken in the southeast and northeast part of Barrang Lompo Island. Result of the present study, showed that all of 2 stations in Barang Lompo Islands were dominated by 5 species of seagrasses such as Cymodocea serullata, Syringodium isoetifolium, Halophila minor, Halodule uninervis, and Thalassia hemprichii. About 70 genera of macrozoobenthos have been found in all observed stations comprised of 53 families, 7 classes, and 4 phyla. Macrozoobenthos diversity index relatively higher in seagrass beds compared to bare area. However, homogenity index in seagrass beds as well as bare area was high and was relatively homogen. Thalassia hemprichii, Cymodocea serullata and Syringodium isoetifolium are the main species in this area with high densitiy. Results of Principal Component Analysis (PCA) showed that seagrass with higher density were able to trap amount of total organic material in the substrate. Macrozoobenthos density were directly proportional with seagrass density and total organic material. Gastropods are commonly found in seagrass bed with higher density and higher total organic material. In contrast with the results mention above, bivalve are more common in bare area. Coastal waters with higher clay sediment concentration may able to trap higher suspended particles than those within sandy and silty sediment.
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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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