Judul: Laju Peluruhan Bakteri Fosfat oleh  Bakteri Sedimen Pada Ekosistem Lamun di Pulau Pramuka, Kepulauan Seribu, DKI Jakarta
Abstrak: Lamun (seagrass) adalah tumbuhan tingkat tinggi berbunga yang dapat tumbuh dengan baik pada lingkungan laut dangkal. Pertumbuhan lamun dipengaruhi oleh beberapa faktor salah satunya nutrien yaitu fosfat. Fosfat di sedimen biasanya tidak bisa digunakan langsung oleh lamun dikarenakan terikat dengan mineral lain sehingga dibutuhkan organisme lain untuk membantu mineralisasi fosfat di alam dan salah satunya adalah bakteri. Penelitian dilakukan untuk mengisolasi bakteri peluruh fosfat pada sedimen serta mengetahui pengaruh laju peluruhan fosfat terhadap kerapatan lamun yang berada di Pulau Pramuka. Hasil isolasi bakteri peluruhan fosfat menggunakan media Pikovskaya diperoleh 28 isolat. Hubungan antara bakteri peluruh fosfat dengan kerapatan lamun dilakukan menggunakan analisis persen korelasi, uji one way ANOVA, regresi linier sederhana serta uji fisiologis untuk mengetahui genus dari bakteri peluruh fosfat. Hasil uji menunjukkan bahwa pengaruh peluruhan fosfat oleh bakteri dengan kerapatan lamun memiliki keterikatan sebesar 16% dan 14%. Korelasi jenis lamun Thallasia hemprichii dan Enhalus acoroides memiliki nilai korelasi yang rendah sementara Cymodocea rotundata serta Halophila ovalis memiliki korelasi kuat. Hasil uji fisiologis diketahui bakteri termasuk dalam genus Pseudomonas dan Actenobacter., Seagrass is a flowering higher plant that can grow well in shallow marine environments. Seagrass growth is influenced by several factors, one of which is nutrients, namely phosphate. Phosphate in sediments usually cannot be used directly by seagrasses because it is bound with other minerals so that other organisms are needed to help mineralize phosphate in nature and one of them is bacteria. The research was conducted to isolate phosphate-degrading bacteria in the sediment and determine the effect of phosphate decay rate on seagrass density in Pramuka Island. The results of isolation of phosphate decay bacteria using pikovskaya media obtained 28 isolates. The relationship between phosphate decay bacteria and seagrass density was carried out using percent correlation analysis, One Way ANOVA test, Simple linear regression, and physiological test to determine. the genus of phosphate decay bacteria. The test results show that the effect of phosphate decay by bacteria with seagrass density has an attachment of 16% and 14%. The correlation of seagrass species Thallasia hemprichii and Enhalus acoroides has a low correlation value while Cymodocea rotundata and Halophila ovalis have a strong correlation. The results of physiological tests showed that the bacteria belonged to the genus psedumonas and actenobacter.
Keyword: Actenobacter, phosphate, phosphate decaying bacteria, physiological, Pseudumonas, seagrass

Judul: Evaluation of Seagrass Habitat Conditions Through Analysis of Seagrass Community Structure on Pramuka Island, Seribu Islands
Abstrak: Lamun memiliki peran penting bagi kehidupan biota laut sebagai produsen primer dan penyusun habitat perairan. Kualitas air dan kandungan substrat berpengaruh terhadap kelimpahan lamun di suatu perairan. Penelitian ini bertujuan untuk menganalisis hubungan antara kualitas habitat yaitu kualitas air dan kandungan substrat dengan struktur komunitas padang lamun. Penelitian ini dilakukan pada bulan November 2023 di Pulau Pramuka, Kepulauan Seribu, DKI Jakarta. Pengambilan data dilakukan di tiga stasiun meliputi pengambilan data lamun dengan tiga line transect di setiap stasiun, pengambilan data kualitas air, dan pengambilan contoh sedimen. Hasil penelitian menunjukkan terdapat 5 jenis lamun yang ditemukan yaitu T. hemprichii, E. acoroides, C. rotundata, H. ovalis, dan S. isoetifolium. Kerapatan dan penutupan tertinggi didapatkan oleh jenis T. hemprichii di tiga stasiun. Hasil analisis menunjukkan, kerapatan lamun memiliki hubungan positif dengan suhu, salinitas, oksigen terlarut, dan C-organik namun memiliki hubungan negatif dengan pH dan substrat pasir kasar. Kandungan karbon organik pada substrat dipengaruhi oleh komposisi sedimen dan kandungan karbon pada lamun dipengaruhi oleh kerapatan. Hal ini menunjukkan kondisi lingkungan perairan berpengaruh terhadap struktur komunitas lamun., Seagrasses have an important role for marine life as primary producers and aquatic habitat builders. Water quality and substrate content affect the abundance of seagrass in a body of water. This study aims to analyze the relationship between habitat quality, namely water quality and substrate content with seagrass community structure. This research was conducted in November 2023 on Pramuka Island, Thousand Islands, DKI Jakarta. Data collection was carried out at three stations including seagrass data collection with three line transects at each station, water quality data collection, and sediment sampling. The results showed that there were 5 seagrass species found, namely T. hemprichii, E. acoroides, C. rotundata, H. ovalis, and S. isoetifolium. The highest density and closure were obtained by T. hemprichii species in three stations. The analysis showed that seagrass density had a positive relationship with temperature, salinity, dissolved oxygen, and C-organic but had a negative relationship with pH and coarse sand substrate. Organic carbon content in the substrate was influenced by sediment composition and carbon content in seagrass was influenced by density. This shows that the condition of the aquatic environment affects the structure of the seagrass community.
Keyword: C-organik, Kualitas air, lamun, sedimen

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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