Dynamic of Sea Level Anomaly of Indonesian Waters

A trend in sea level rise as a result of global warming could be a threat to small islands and coastal areas in Indonesia. The objective of this study was to determine the trend and variability of mean sea level anomaly (MSLA) in Indonesian waters during the 20 years of observation. The data used in this study were monthly MSLA data obtained from the AVISO website (ftp://ftp.aviso.oceanobs.com). Supporting data were the Southern Oscillation Index (SOI) (http://www.gom.gov.au/climate/enso), Dipole Indian Mode (DIM) index (http://gcmd.nasa.gov/records/GCMD_Indian_Ocean_Dipole.html), and the Pacific Decadal Oscillation (PDO) index (http://research.jisao.washington.edu/pdo/). Eigth stations of Indonesian waters were selected to study the variability of MSLA. In general, MSLA variabilities of Indonesian waters had a seasonal pattern, positively correlated with the SOI index, and negatively correlated with DIM and PDO indexes. The partial correlation of DIM was more dominant in west of Sumatra (r=-0.52) and south of Java (r=-0.44), PDO was more dominant in the northern waters of Papua (r=-0.37) and Makassar Strait (r=-0.33), and SOI was more dominant in northern Papua (r=0.52) and less toward the west of Indonesian waters. Overall, the MSLA variability of Indonesian waters can be explained by the variabilities of SOI, DIM, and PDO indexes with the lowest value in Natuna waters by 12% (R2=0.12) and the highest value in the northern waters of Papua by 54% (R2=0.54). Interannual variabilities were observed during ENSO events (SOI<-10) along with the maximum value of DIM index resulted in the lowest value of MSLA. Meanwhile, the highest value of MSLA was found during La Nina events (SOI>10) in conjunction with a minimum value of DIM and PDO indexes. The average rate of sea level rise in Indonesian waters was 5.84 mm/yr, almost two times higher than the average rate of global sea level rise (3.2 mm/yr)

POTENTIAL TSUNAMI ANALYSIS IN NORTH LOMBOK

Sesar Flores merupakan pemicu gempa bumi pada tanggal 5 Agustus 2018 di Pulau Lombok. Dilaporkan bahwa gempa bumi dengan kekuatan 7,0 Mw saat itu, telah menyebabkan tsunami kecil dengan ketinggian 13,5 cm di pesisir pantai Desa Carik, Lombok Utara. Studi ini bertujuan untuk mensimulasikan potensi bahaya tsunami yang berasal dari aktivitas sesar Flores menggunakan pemodelan tsunami COMCOT v1.7 untuk mengestimasi potensi tinggi tsunami, waktu tiba tsunami, dan potensi area terdampak tsunami. Data historis untuk pusat gempa bumi dalam simulasi adalah gempa bumi pada tanggal 2 September 2018, dengan asumsi kekuatan gempa 7,0 Mw. Berdasarkan data gempa bumi diatas, parameter yang dipilih berupa kedalaman sumber gempa 14 km, luas patahan 47,9 x 15,9 km, dislokasi 2,5 m, dan parameter strike 284o, dip 64o, dan slip 88o. Layer simulasi dibagi menjadi 3 berdasarkan sistem model bersarang, dengan reolusi masing-masing 464 m, 232 m, dan 77 m. Data batimetri diperoleh dari GEBCO dengan resolusi 15-arcsecond. Waktu simulasi penjalaran tsunami yang dilakukan selama 30 menit, menghasilkan tinggi tsunami awal sebesar 0,9 m. Tinggi tsunami maksimum yang teramati di darat adalah 1–2,5 m. Estimasi waktu tiba gelombang pada pesisir Lombok Utara, adalah 3 sampai 13 menit. Hasil pemodelan menunjukkan bahwa wilayah Kecamatan Bayan, Kayangan, Tanjung, dan Gangga berpotensi terkena dampak tsunami. Tinggi maksimum dan kecepatan waktu tiba tsunami di Lombok Utara sangat berpotensi merusak dan dapat menimbulkan korban jiwa, sehingga perlu upaya mitigasi seperti sosialisasi dan pelatihan dalam menghadapi bahaya tsunami, penanaman vegetasi pantai yang sesuai dengan substrat di pantai, dan membangun pemecah gelombang lepas pantai.The Flores Fault is the one of caused an earthquake on August 5, 2018 in Lombok Island. It is reported that this earthquake with magnitude of 7.0 Mw caused a small tsunami with amplitude of 13.5 cm in the coastal area of Carik village, North Lombok. This study aimed to simulate a potential tsunami hazard from the Flores faults activity using the COMCOT v1.7 tsunami model which estimates potential tsunami height, tsunami arrival time, and potential tsunami affected areas. Historical earthquake data as an epicenter in the simulation was the earthquake on September 2, 2018, with the earthquake magnitude of 7 Mw. On the basis of the earthquake above, the model parameters was chosen, such as the depth of epicenter of 14 km, width fault area of ​​47.9 x 15.9 km, dislocation of 2.5 m, strike of 284o, slip of 64o, and dip of 88o. Simulation layer is divided into 3 layers based on nesting grid system with 464 m, 232 m and 77 m resolution, respectively. Bathymetric data were obtained from GEBCO with a 15-arc second grid size. Tsunami propagation simulation has been performed for duration of 30 minutes, which produced an initial tsunami height of 0.9 m. The maximum tsunami height revealed from the simulation was between 1-2.5 m on land. Estimated arrival time of the tsunami in North Lombok was ftom 3 to 13 minutes. Simulation result showed that sub-district area of Bayan, Kayangan, Tanjung, and Gangga are affected potentially areas by the tsunami. The maximum height and arrival time of the tsunami in North Lombok have the potential to be destructive and can cause casualties, so that mitigation efforts are needed, such as socialization and training in dealing with tsunami hazards, planting coastal vegetation that is suitable for the substrate on the coast, and building offshore breakwaters. &nbsp

Population Structure And Morphometry Of Horseshoe Crab Carcinoscorpius Rotundicauda, Latreille 1802 In Kampung Gisi Coastal Area Of Bintan Bay Of Riau Islands Province

Horseshoe crab, Carcinoscorpius rotundicauda is frequently found in the coastal zone of Bintan Bay of Riau Islands Province. The study was conducted from August to September 2016 in coastal area of Kampung Gisi, Bintan bay. The aims of the study were to analyse the population structure and morphometric characters of horseshoe crab and its relation to the coastal environmental characteristics. Sampling of horseshoe crab was taken using belt transect method, and coastal environmental parameters were measured in-situ. The results show that b values of length-weight relationship were found to be 3.3 (male) and 2.6 (female) respectively. Furthermore, the growth pattern of males were positive allometric, and females were negative allometric. Horseshoe crab are closely related to sandy mudflats sediment, brackish water salinity and mangrove habitat distribution

Tidal Range Calculation Based on the Local Knowledge of the Sama Ethnic Group in the Eastern Indonesia

The Sama ethnic group (Bajo) is well known as “Indonesian marine people” that dominantly spreaded in coastal region of eastern Indonesian region. Their activities have been adapting with the territorial water as shown in the determination of their home floor height to prevent from the tidal flood. The purpose of this study was to examine the accuracy of the tidal range calculation by local knowledge of the Sama ethnic group (Sama Ethnic Method, SEM). The analysis was done by comparing tidal range result calculated by the Sama Ethnic Method (SEM) with the standardized tidal harmonic constituents. The result showed that the 2nd tidal peaks (DLB-s) in the 15th “Sya'ban” date was the best date to do measurement of a tidal range. In this case, the “Likkas Silapas” (LS) value at the above date was above the mean height water level (MHWL). Meanwhile, in other dates, the LS value was under MHWL value. The result also showed a strong correlation (R2> 90%) between rasio of tidal high on 1st and 2ndpeaks (DLB-s/DLB-m) on 15th Sya'ban date and LS-s value. The local knowledge of the Sama Ethnic Method to determine the tidal range was effective and scientifically proven

Amplitude Variations of Tidal Harmonic Constituents in Bitung Station (Variasi Amplitudo Konstituen Harmonik Pasang Surut Utama di Stasiun Bitung)

Perhitungan konstituen harmonik pasang surut masih menggunakan metode konvensional, pengembangan metode dominan pada sistem komputasinya dan menggunakan sistem penanggalan Masehi. Penelitian ini bertujuan untuk mengetahui, apakah amplitudo konstituen harmonik yang dihitung dari pengelompokan data berdasarkan penanggalan Hijriah memberikan karakter yang relatif sama (stabil) dibulan yang sama dibandingkan dengan penanggalan Masehi. Perbandingan tersebut dilakukan pada 10 konstituen harmonik utama pasang surut, guna membandingkan perhitungan tunggang air dari nilai konstituen dan dari Metode Suku Sama (MSS). Hasil analisis data menunjukkan bahwa nilai deviasi amplitudo sangat kecil dari masing-masing konstituen harmonik pada perhitungan berdasarkan sistem kalender Hijriah, dimana amplitudo pada bulan Sya’ban relatif stabil dan lebih tinggi dibandingkan pada bulan lainnya. Nilai koefisien determinan (R2) untuk data awal pasang surut pada fase bulan baru (BB) dan bulan purnama (BP) lebih tinggi dibandingkan data awal pada fase bulan lainnya. ANOVAmenghasilkan konstituen K1dan S2terpengaruh jika data dimulai saat fase bulan kuartil I (KW1) dan purnama (BP), sedangkan saat fase awal kuartil 2 (KW2) terjadi pada konstituen P1 dan K2, MS4 dan M4. Dengan demikian, perhitungan amplitudo konstituen harmonik lebih optimum jika data dimulai saat fase bulan baru atau mengikuti penanggalan Hijriah

Analisis Hambur Balik Akustik untuk Klasifikasi dan Pemetaan Substrat Dasar Perairan di Teluk Yos Sudarso, Kota Jayapura

Penelitian ini bertujuan untuk mengkaji karakteristik kuat hambur Balik akustik dasar perairan. Echosounder bim tunggal Simrad EK15 frekuensi 200 kHz digunakan untuk perekaman data hidroakustik yang dilaksanakan pada tanggal 29 April sampai 2 Mei 2017 di perairan Teluk Yos Sudarso, Kota Jayapura, Provinsi Papua. Pengambilan contoh substrat digunakan untuk data validasi menggunakan sedimen grab. Pengolahan data hasil rekaman akustik menggunakan satuan dasar pencuplikan sebesar 100 ping data perekaman dengan ambang batas nilai E1 adalah -50 dB dan E2 adalah -70 dB. Hasil penelitian menunjukkan bahwa terdapat perbedaan yang signifikan nilai hambur Balik akustik antar tipe substrat dasar perairan. Nilai E1 karang -15,62 dB dan E2 -30,70 dB, untuk substrat pasir E1 berkisar antara -28,40 dB sampai -27,36 dB dan E2 berkisar antara -50,96 dB sampai -47,44 dB, sedangkan substrat lumpur E1 berkisar antara -37,81 dB sampai -35,99 dB dan E2 berkisar antara -62,85 dB sampai -54,12 dB. Ukuran butiran substrat sangat berpengaruh terhadap kuat hambur Balik akustik dasar perairan. Berdasarkan hasil deteksi akustik, substrat karang berada pada kedalaman 2-3 m, substrat pasir pada kedalaman 2-10 m, dan substrat lumpur dominan pada kedalaman lebih dari 10 m

Relationship Between Characteristics of Marine Debris and Impact to Coral Reef

HighlightMarine debris can be as a treat for coral reefBranching coral is the most affected by marine debrisPlastic marine debris commonly found in all research location, especially from fisheries and daily activityAbstractA coral reef is one of the important ecosystems, however, the existence of coral reef is threatened. Several factors can be a threat to the coral reef, such as marine debris. Research about marine debris on coral reefs in Indonesia has not much been done. This research aims to identify marine debris that is found and impacted, to identify the impacts caused, and to identify the life forms most susceptible to being affected. This research was conducted in Kelapa Island, Kelapa Dua Island, and Harapan Island by using the Belt Transect method sized 20 x 4 m2 with four repetitions at each station to determine coral reef life form, and type of marine debris. The data was analyzed by using the Correspondence Analysis (CA) to determine the correlation of marine debris and the affected life forms of coral reefs. The result showed the plastic marine debris was found in all stations. Six life forms were affected by marine debris, and the most susceptible life forms that affected were massive and branching. The most dominant impact category on coral reefs was tissue loss with algal growth (TLAG)

Hutan mangrove di Pulau Ternate secara spasial dan temporal

Hutan mangrove merupakan vegetasi yang sangat penting di wilayah pesisir pantai.  Keberlanjutan hutan mangrove perlu mendapat perhatian memiliki beberapa fungsi yang meliputi fungsi ekologi, fungsi fisik, dan ekonomi.  Penelitian ini bertujuan untuk mengetahui status hutan mangrove berdasarkan indeks ekologi dan menganalisis spasial temporal luas hutan mangrove di Pulau Ternate.  Metode yang digunakan dalam penelitian ini adalah survey pengukuran data lapangan yang di laksanakan di Kelurahan Mangga Dua, Kelurahan Gambesi dan Kelurahan Rua. Spasial temporal menggunakan data citra resolusi tinggi yang bersumber dari Google Earth  selama 20 tahun dengan akuisisi lima waktu perekaman  yaitu tahun 2022, 2020, 2015 2010 dan 2001 dengan aplikasi Sistem Informasi Geografis (SIG).  Hasil penelitian diperoleh informasi status hutan mangrove di Kelurahan Mangga Dua, Kelurahan Gambesi dan Kelurahan Rua dengan menggunakan beberapa indicator indeks ekologi diketahui dalam kondisi rusak hingga  kondisi sedang. Luas mangrove di Pulau Ternate pada tahun 2002 adalah 5.97 ha dan mengalami penurunan luas area sampai tahun 2022 menjadi 2.51 ha. Degradasi kondisi hutan mangrove di Pulau Ternate perlu diantisipasi dengan model pengelolaan berkelanjutan dan penerapan konsep transdisipliner. Kata kunci : Biodiversitas, degradasi, pesisir, pulau kecil, tropis