Judul: Recordings On Sea Surface Temperature And Metals Pollution From Coral Reefs Sclerochronology
Abstrak: The aragonite skeleton of massive reef-building corals contain a record of the oceanic environment in which they grow. This proxy measurement is very important to understand past environmental condition due to the lack of instrumental records, and as basis how to manage it in the present and in the future. This research objectives are to find out the ability U/Ca ratio in showing SST fluctuations and to know metals fluctuation in the waters from corals sclerochronology. The robustness of U/Ca ratio was assessed by comparing it with local SST data set achieved by NOAA satellite due to period of 1983-2002. Porites stephensoni is used as samples, took from Seribu Islands – Jakarta, in specific Bokor Island, Tikus Island, and Tidung Island. Samples are analyzed with neutron activation analyses (NAA) to measure elements concentration, except for Pb and Cd we used atomic absorbance spectrometer (AAS). The U/Ca ratio show very weak correlation with yearly SST variations, with r2 = -0.23 (Tikus Island), r2 = -0.35 (Tidung Island), and r2 = -0.39 (Bokor Island). U/Ca ratio can not be used for showing SST variation at Seribu Islands waters. Sclerochronology show that metals pollution did happen, noticed by metal/Ca ratio that higher then its background value. Arsenic (As) is not naturally habits in corals skeleton, while the other metals (Sb, Pb, Cd, Co, Cr) seem naturally habit in it. Applying principal component analysis to all samples data set has resulted in categorizing them into one group. It show that those three island has similar water quality or they were influenced by the same water-mass. They have one general source for all the metals, except arsenic (As).
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Judul: The Approximation of Coral Reef Ecosystem Quality in The Seribu Islands Using Benthic Foraminifera Proportion as Bioindicator
Abstrak: Coral reef ecosystem is one of mega biodiversity environments with the highest ecological pressure especially caused by human activities. Local impact like nutrification will decrease water quality and the ecosystem. Benthic foraminifera as bioindicator can be used as early monitoring tool to observe the changes in reef ecosystems. Therefore the aims of this study were to investigate the distribution of benthic foraminifera in reef ecosystem and determine the relationship between coral ecosystems with FORAM Index as tool for benthic foraminifera to asses waters quality. Eleven stations from Karang Bongkok, Pramuka, and Onrust on Seribu Island were used for this study. Nutrient and physical parameters were measured in situ and in the laboratory. The foraminifera was separated from sediment and indentified by binocular microscope. The foraminifera then classified by functional group and calculated by FORAM Index formula (FI). The range of FI was from 3,4-8,2, which indicated marginal to suitable environment for reef development. The modification of FI (FIm) showed that the range from 1,2-5,2 where there were unsuitable environment for reef growth in Onrust Island. The results showed that Calcarina and Amphistegina are indicators of reef health ecosystem. Nevertheless, FORAM Index can be applied in Indonesia waters with some modification with considering the preference of the habitat.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf