Judul: Studi Produktivitas Primer Mikrofitobentos di Perairan Pulau Lancang, Kepulauan Seribu
Abstrak: Vast and bare substrate area in euphotic zone is not only served as habitat for macroscopic vegetation, but also photosynthetic microorganisms whose abundance is dominating the upper sediment surface. These microorganisms are composed of microalga colonies, called microphytobenthos, living attached to sediment particles. Hence, their existence is sometimes neglected. Microphytobenthos taxonomy is basically the same with pelagic phytoplankton. Another similarity is their photosynthetic characteristic which requires light as the main energy source in photosynthesis (Underwood and Kromkamp, 1999; Urban-Malinga and Wiktor, 2003). Microphytobenthos were easily resuspended to the water column and representing more than 50% of total cholorophyll concentration, then become available as food source for deposit feeder and suspension feeder. The only difference between pelagic phytoplankton and microphytobenthos is their habitat preference. Besides playing an important role in shallow water food chain, microphytobenthos also give contribution to sediment stability, by excreting extracellular polymeric substances (EPS) and influence nutrient flux on sediment – water boundary through their photosynthetic and metabolic activity. However, microphytobenthic community and their primary productivity, particularly in Indonesian waters, were still less studied. Measurement of primary productivity was usually performed only at the surface or water column, neglecting the primary production by sediment-associated microalgae. Research on microphytobenthic community and primary productivity is important since they perform significant role in carbon fixation, particularly in shallow water system, where sunlight intensity still penetrates and reach the sediment surface. The aim of this study is to investigate microphytobenthic primary productivity and estimate the contribution of microphytobenthos contribution towards entire aquatic primary productivity. In this study, primary productivity estimation was based on photosynthetic process by calculating the difference of oxygen concentration before and after photosynthesis. Primary productivity of microphytobenthos in Pulau Lancang was higher compared to that in surface layer. Results from third-day experiment shown an extremely high value from microphytobenthos primary production, reached up to 29 times of surface layer primary productivity. Average of microphytobenthos primary productivity was 42.32 mg C m-3 hour-1, almost two fold higher than phytoplankton primary productivity which was 22.46 mg C m-3 hour-1. Results from pigment analysis using spectrophotometer shown that chlorophyll-a concentration in sediment surface was 4496.08 – 8937.12 mg l-1, much higher than those in surface layer, 0.0003339 – 0.000544 mg l-1. These results were in line with high primary productivity at the sediment surface which strongly caused by the abundant biomass of sediment-associated benthic vii microalgae. According to the measurement of physical and chemical parameters, light intensity was considered as the main factor supporting microphytobenthos primary productivity. Microphytobenthos primary productivity alone cannot describe the entire aquatic productivity since there are a lot of other autotrophic components such as seagrass and mangrove that compose marine ecosystem of Pulau Lancang. However, significant contribution of microphytobenthos indicates that microphytobenthos is feasible to be considered as important component in the study of coastal primary productivity.
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Judul: Mangrove and Seagrass Ecosystem Contribution to Coastal  Water Productivity
Abstrak: Produktivitas perairan, yang didominasi oleh produksi bahan organik oleh fitoplankton, merupakan faktor penting dalam siklus karbon dan jaring-jaring makanan laut, sangat dipengaruhi oleh input nutrien dari ekosistem mangrove dan lamun. Ekosistem mangrove dan lamun berperan vital dalam siklus nutrien dengan mempengaruhi kesuburan perairan melalui proses produksi dan ekspor bahan organik, yang esensial untuk mendukung kehidupan plankton dan berdampak pada produktivitas perikanan. Pendekatan menggunakan pemodelan dinamik memungkinkan pemantauan efektif dan pemahaman terhadap kontribusi ekosistem ini terhadap dinamika nutrien dan kesuburan perairan, terutama di wilayah Kepulauan Seribu. Penelitian ini berfokus pada karakteristik lingkungan dan ekosistem mangrove, struktur ekosistem lamun, serta dinamika dan konektivitas nitrogen di ekosistem mangrove, lamun, dan lamun-mangrove. Terdapat perbedaan signifikan antara pulau besar (BJBR Probolinggo) dan pulau kecil (Pulau Pramuka, Tidung Kecil) dalam hal jenis mangrove yang dominan, karakteristik sedimen, dan faktor fisik serta kimia yang memengaruhi pertumbuhan mangrove. Analisis diskriminan menyoroti perbedaan karakteristik ekosistem mangrove antar lokasi, dengan BJBR Probolinggo menunjukkan keragaman spesies dan kerapatan pohon yang lebih tinggi. Lingkungan di pulau kecil lebih dipengaruhi oleh faktor lokal seperti sedimen dan karakteristik fisika-kimia, sementara BJBR Probolinggo mendapatkan kontribusi bahan organik yang kaya nutrien dari aliran sungai. Struktur ekosistem lamun di Pulau Pramuka dan Pulau Tidung Kecil menunjukkan perbedaan signifikan dalam kerapatan lamun antara dua pulau, dengan Pulau Pramuka memiliki kerapatan lebih tinggi dan variasi jenis lamun yang lebih besar. Model nutrien, fitoplankton, dan klorofil-a mengeksplorasi dinamika dan konektivitas nitrogen di ekosistem mangrove, lamun, dan lamun-mangrove. Simulasi dilakukan selama dua tahun, dan hasilnya menunjukkan ekosistem lamun mangrove menunjukkan kelimpahan fitoplankton tertinggi, diikuti oleh ekosistem lamun dan ekosistem mangrove. Hasil simulasi mengidentifikasi bahwa perubahan dalam nitrogen inorganik terlarut di air (DIN) memengaruhi secara langsung kelimpahan fitoplankton dan konsentrasi klorofil-a pada ekosistem lamun mangrove. Secara keseluruhan penelitian ini memberikan gambaran tentang dinamika dan interaksi antara ekosistem mangrove, lamun, dan lamun-mangrove di Kepulauan Seribu. Temuan ini mendukung perlunya pemeliharaan ekosistem lamun-mangrove dan penerapan lebih lanjut penelitian untuk memahami lebih baik dinamika fitoplankton secara menyeluruh.
Keyword: fitoplankton, klorofil-a, nitrogen, nutrien, model simulasi, interaksi  biogeokimia

Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
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