Judul: Spatial Distribution of Benthic Communities in The Kepulauan Seribu Marine National Park, DKI Jakarta
Abstrak: Dalam beberapa dekade terakhir, diketahui bahwa tutupan terumbu karang di Kepulauan Seribu mengalami degradasi akibat dari pengaruh non-antropogenik (perubahan ekologis, faktor alam) dan pengaruh antropogenik (kegiatan manusia) seperti pariwisata dan perikanan tangkap. Taman Nasional Kepulauan Seribu memiliki sistem zona pengelolaan perairan yang berfungsi melindungi ekosistem bahari yang ada di dalamnya seperti ekosistem terumbu karang. Terdapat empat zona perairan yaitu ada zona inti, zona perlindungan, zona pemanfaatan wisata, dan zona pemukiman. Penelitian ini bertujuan mengetahui sebaran komunitas bentik, sebaran lifeform karang keras, dan sebaran genus karang lunak serta persentase tutupannya berdasarkan zonasi di Perairan Taman Nasional Kepulauan Seribu, DKI Jakarta. Metode yang digunakan adalah Underwater Photo Transect dengan ukuran 58 cm x 44 cm. Berdasarkan pengamatan di empat zona perairan tersebut, diketahui bahwa kategori abiotic merupakan yang tertinggi dibandingkan dengan enam kategori lainnya dengan total nilai tutupan berada pada rentang 40 - 50%. Kondisi tutupan karang keras hidup di perairan zona inti, zona pemanfaatan, dan zona pemukiman masuk ke dalam kategori cukup (25 - 49,9%). Adapun tutupan karang keras hidup di perairan zona perlindungan masuk ke dalam kategori buruk (0 - 24,9%). Sebaran genus karang lunak pada zona inti didominasi oleh genus Sarcophyton (0,28%), zona pemanfaatan oleh genus Gorgonian (0,13%), zona pemukiman oleh genus Gorgonian (1,04%), dan zona perlindungan oleh genus Nephthea (0,15%)., In the last few decades, it has been known that coral reef cover in the Kepulauan Seribu has been degraded as a result of non-anthropogenic influences (ecological changes, natural factors) and anthropogenic influences (human activities) such as tourism and capture fisheries. The Kepulauan Seribu Marine National Park has a water management zone system that functions to protect the marine ecosystems in it such as coral reef ecosystems. There are four water zones, namely the core zone, protection zone, tourism utilization zone, and residential zone. This study aims to determine the distribution of benthic communities, distribution of hard coral lifeforms, and distribution of soft coral genera and their percentage of cover based on zoning in the waters of the Kepulauan Seribu Marine National Park, DKI Jakarta. The method used is Underwater Photo Transect with a size of 58 cm x 44 cm. Based on observations in the four water zones, it is known that the abiotic category is the highest compared to the other six categories with a total cover value in the range of 40 - 50%. The condition of living hard coral cover in the waters of the core zone, utilization zone, and settlement zone was in the sufficient category (25 – 49,9%). As for the live hard coral cover in the waters of the protection zone, it is in the bad category (0 – 24,9%). The distribution of soft coral genera in the core zone is dominated by Sarcophyton (0,28%), the utilization zone by Gorgonian (0,13%), the settlement zone by Gorgonian (1,04%), and the protection zone by Nephthea (0,15%) .
Keyword: category, coral, cover, Kepulauan Seribu Marine National Park, zone

Judul: Analysis of Coral Reefs Ecosystem and Coral Fish Risk  Assessment in Kepulauan Seribu
Abstrak: Faktor alam dan antropogenik telah menimbulkan dampak dan risiko terhadap kesehatan terumbu karang dan biota asosiasinya di Kepulauan Seribu. Penelitian ini bertujuan menentukan tingkat risiko ekosistem terumbu karang dan ikan karang sebagai dasar strategi pengelolaan di Kepulauan Seribu. Penelitian dilakukan pada bulan Juli 2019 dari kegiatan pemantauan ekosistem terumbu karang dan ikan karang DKI Jakarta tahun 2019. Kemudian, dilakukan analisis tingkat risiko dengan pendekatan indeks kerentanan serta komposisi jenis ikan karang indikator. Secara keseluruhan, ekosistem terumbu karang pada lokasi penelitian memiliki tingkat kerentanan sedang dengan kondisi tutupan karang berada dalam kategori cukup baik, kategori mortalitas karang sedang, dan potensi keterpaparan cukup tinggi. Komposisi jenis ikan karang indikator didominasi oleh kategori sedang. Secara keseluruhan, Kepulauan Seribu khususnya Kepulauan Seribu Utara didominasi oleh tingkat risiko rendah. Terdapat enam pulau tergolong tingkat risiko tinggi dengan kategori setiap parameter mengkhawatirkan yaitu Pulau Kuburan Cina, Pulau Putri Timur, Pulau Melintang Besar, Pulau Semut Besar, Pulau Sebaru Besar, dan Pulau Rengat. Tingkat kerentanan dan komposisi jenis ikan karang indikator dipengaruhi oleh kegiatan pariwisata, penangkapan ikan, dan keberadaan angin musim., Natural and anthropogenic factors have had impacts and risks to the health of coral reefs and their associate biota in the Kepulauan Seribu. The objective of the research is to determine the risk level of coral reef ecosystems and coral fish as the basis of management strategies in the Kepulauan Seribu. The research was conducted on July 2019 from the monitoring activities of DKI Jakarta's coral reef and coral fish ecosystems in 2019. The susceptibility index approach and the composition of the type of coral fish indicator were used to gain a risk level analysis. Overall, coral reef ecosystems at the research site had a medium level of susceptibility with coral coverage conditions being in the category of quite good, medium coral mortality category, and high enough exposure potential. The composition of the coral fish indicator is dominated by the medium category. Overall, Kepulauan Seribu especially the Northern Kepulauan Seribu was dominated by low-risk levels. There are six islands classified as high-risk levels with the category of each alarming parameter, namely Kuburan Cina Island, Putri Timur Island, Melintang Besar Island, Semut Besar Island, Sebaru Besar Island, and Rengat Island. The level of susceptibility and composition of the type of coral fish indicator was influenced by the presence of tourism activities, fishing, and the presence of wind seasons.
Keyword: ikan karang indikator, kerentanan, keterpaparan, mortalitas, tingkat risiko

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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