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: Hubungan Kelimpahan Makrozoobenthos dengan Karakteristik Habitat di Perairan Pulau Pramuka dan Pulau Panggang
Abstrak: Makrozoobenthos menghuni berbagai habitat perairan dan umumnya ditemukan berasosiasi erat dengan substrat dasar perairan. Penelitian ini bertujuan untuk mencari keterkaitan karakteristik substrat habitat dengan kelimpahan spesies makrozoobenthos di perairan Pulau Pramuka dan Pulau Panggang, Kepulauan Seribu, DKI Jakarta. Pengamatan data makrozoobenthos dilakukan dengan metode transek sabuk yang dimodifikasi pada tiga stasiun dengan kondisi habitat yang berbeda, serta dilakukan pengambilan data komunitas bentik dengan metode Line intersect transect dan pengukuran data kualitas perairan pada tiap stasiunnya. Hasil pengamatan pada Pulau Pramuka dan Pulau Panggang menunjukkan terdapat 6 filum, 29 famili, dan 45 spesies makrozoobenthos. Jumlah total relatif makrozoobenthos yang ditemukan pada ketiga stasiun berjumlah 410 individu/602. Ketiga stasiun memiliki jumlah kelimpahan relatif makrozoobenthos dan spesies makrozoobenthos yang berbeda, dimana Stasiun 1 yang terletak diantara Pulau Pramuka dan Pulau Panggang memiliki kelimpahan relatif tertinggi dan Stasiun 3 yang terletak di bagian barat daya Pulau Panggang memiliki kelimpahan relatif terendah. Hasil analisis korespondensi menunjukkan jika beberapa spesies makrozoobenthos memiliki kaitan yang erat terhadap substrat habitatnya. Makrozoobenthos yang berasal dari filum Moluska, khususnya Pedum spondyloideum berkelompok dengan kondisi substrat yang memiliki hard coral, sedangkan terdapat juga makrozoobenthos berspesies Phyllidia varicosa yang tidak berkelompok dengan jenis substrat apapun., Macrozoobenthos inhabit various aquatic habitats and are commonly found closely associated with the substrate of the water bottom. This research aims to find the relationship between habitat substrate characteristics and the abundance of macrozoobenthos species in the waters of Pramuka Island and Panggang Island, Seribu Islands, DKI Jakarta. Macrozoobenthos data observations were carried out using a modified belt transect method at three stations with different habitat conditions. Additionally, benthic community data were collected using the Line intersect transect method, and water quality data were measured at each station. The observation results on Pramuka Island and Panggang Island showed that there were 6 phyla, 29 families and 45 macrozoobenthos species. The total relative abundance of macrozoobenthos found at all the three stations was 410 individuals/602. The three stations have different relative abundances of macrozoobenthos and macrozoobenthos species, where Station 1 that located between Pramuka and Panggang island has the highest relative abundance and Station 3 that located at southwest of Panggang island has the lowest relative abundance. The results of the correspondence analysis show that several macrozoobenthos species have a close relationship to their habitat substrate. Macrozoobenthos from the Mollusca phylum, especially Pedum spondyloideum, group with bottom substrate that have high hard coral coverage, while there are also macrozoobenthos of the Phyllidia varicosa species that do not group with any type of substrate
Keyword: coral reef, habitat characteristic, macrozoobenthos, substrate

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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