Judul: Morphometric and Biovolumetric Characteristics of Noctiluca scintillans in Marunda Waters, Jakarta Bay
Abstrak: Teluk Jakarta merupakan perairan yang padat akan aktivitas manusia. Padatnya aktivitas manusia dapat berimbas pada peningkatan nutrien dalam perairan. N. scintillans seringkali menyebabkan bloom sebagai akibat dari tingginya nutrient dalam perairan. Karakteristik morfometrik N. scintillans memiliki potensi untuk menjadi indikator kondisi populasi dan lingkungan. Pengukuran diameter sel dilakukan untuk menentukan karakteristik morfometrik dan biovolumetrik populasi N. scintillans di Teluk Jakarta serta melihat perbedaan karakteristik tersebut dengan populasi di perairan beriklim sedang. Pengambilan sampel dilakukan pada Februari 2024 di Pantai Marunda, Jakarta Utara. N. scintillans yang ditemukan di Teluk Jakarta terdiri dari dua bentuk yaitu merah dan hijau. Berdasarkan hasil pengukuran, diameter sel N. scintillans di Teluk Jakarta berkisar dari 183,98 hingga 456,97, Jakarta Bay is an area enduring high pressure of anthropogenic activity. A lot of anthropogenic activity could increase the nutrient amount in the waters. Blooms from N. scintillans often occurred as a result of high levels of nutrients in the water. Morphometric characteristic of N. scintillans has the potential to be an indicator of population and environmental condition. Cell diameter measurements were carried out to determine the population’s morphometric and biovolumetric characteristics of N. scintillans in Jakarta Bay and to see differences in these characteristics with populations in temperate waters. Sampling was carried out in February 2024 on Marunda Beach, North Jakarta. N. scintillans found in Jakarta Bay consist of two form, namely red and green. Based on the measurement results, the cells diameter of N. scintillans in Jakarta Bay ranges from 183.98 to 456.97 µm. This indicates a population that is in the early bloom phase with suitable water conditions. The size of N. scintillans in Jakarta Bay is relatively smaller compared to temperate waters.
Keyword: ImageJ, morfometrik, Biovolume, dinoflagellata, N. scintillans

Judul: Sebaran Konsentrasi Fosfat (PO4-P) dan Nitrat (NO3-N) sebagai Indikator Kesuburan Perairan di Teluk Jakarta
Abstrak: Teluk Jakarta terletak di pantai utara Pulau Jawa merupakan muara bagi 13 sungai besar di Jakarta, Bogor, Depok, Tangerang, dan Bekasi. Berbagai aktivitas yang melibatkan pemanfaatan perairan baik teluk maupun sungai dapat menyebabkan penurunan kualitas perairan dan pengayaan nutrien. Salah satu akibat pengayaan nutrien yaitu peningkatan nutrien seperti fosfat dan nitrat yang dapat memengaruhi produktivitas perairan. Penelitian ini bertujuan menganalisis sebaran konsentrasi fosfat dan nitrat di Teluk Jakarta secara spasial dan temporal. Pemantauan kualitas air dilakukan antara tahun 2012 hingga 2019 sebanyak delapan kali pengamatan dari 23 stasiun. Penentuan 23 stasiun berdasarkan keterwakilan wilayah Teluk Jakarta. Berdasarkan kandungan fosfat dan nitrat, perairan Teluk Jakarta terrmasuk subur. Pola sebaran spasial fosfat dan nitrat konsentrasinya lebih tinggi di sekitar pantai dan semakin rendah seiring mendekati mulut teluk. Secara temporal, konsentrasi fosfat dan nitrat menunjukkan perbedaan yang signifikan cenderung meningkat dari tahun ke tahun., Jakarta Bay is located on the north coast of Java Island and is the mouth of 13 major rivers in Jakarta, Bogor, Depok, Tangerang, and Bekasi. Various activities that involve the use of waters, both bays and rivers, can cause a decrease in water quality and nutrient enrichment. One result of nutrient enrichment is an increase in nutrients such as phosphate and nitrate which can affect water productivity. This study aims to analyze the spatial and temporal distribution of phosphate and nitrate concentrations in Jakarta Bay. Water quality monitoring was carried out between 2012 and 2019 in eight observations from 23 stations. Map of 23 stations based on the representativeness of the Jakarta Bay area. Based on the content of phosphate and nitrate, the waters of Jakarta Bay are considered fertile. The pattern of spatial distribution of phosphate and nitrate concentrations is higher around the coast and lower as they approach the mouth of the bay. Temporally, the concentrations of phosphate and nitrate showed significant differences which tended to increase from year to year.
Keyword: temporal, Jakarta Bay, nitrate, phosphate, spatial

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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