No abstract

Equatorial corals were previously thought not to spawn synchronously at the assemblage level. However, recent studies have reported multi-specific coral spawning events in equatorial regions. Here, we report the reproductive activity of 21 Acropora species in the Karimunjawa Archipelago over five consecutive years (2008-2012). We also infer the month of spawning for Acropora humilis, Acropora gomezi, and Acropora muricata from the presence of mature oocytes. We found that Acropora assemblages exhibit a high degree of inter-specific reproductive seasonality. The highest proportion of colonies with mature oocytes was observed in March 2011 (65%, n = 80). Oocytes likely developed during June-March, 6 to 10 months before spermatogenesis. Spermatocytes were observed in samples collected during March; however, the onset of spermatogenesis could not be precisely determined as samples were not collected in January and February. This was because of weather constraints and difficulty in detecting the early stages of spermatogenesis. Multi-specific spawning events were observed during the first transition period (March-April) and the second transition period (September-October) between monsoons. The number of species containing mature oocytes was higher during March-April (12 species) and September-October (8 species). Spawning patterns likely follow the lunar cycle. However, two distinct spawning events coincided with two periods of higher temperature (March-April and September-October). Daily temperature records indicate that spawning occurred on days where temperature dropped before the expected spawning time during the warming period. During the period of rising temperature, wind speeds were lower, which might serve as a signal leading to the multi-specific spawning of corals in the tropics, at least in the Karimunjawa Archipelago of Indonesia.

Abstract. Indrayanti E, Zainuri M, Sabdono A, Wijayanti DP, Pranowo WS, Siagian HSR. 2019. Larval dispersal model of coral Acropora in the Karimunjawa Waters, Indonesia. Biodiversitas 20: 2068-2075. Identification of connectivity patterns through the larval dispersal dynamics is urgently needed to support the sustainable larval supply. Many studies on the larval coral distribution have been reported. However, no study of coral larval dispersal has been conducted in Karimunjawa. The purpose of this research was to build a model of coral larval dispersal in Karimunjawa waters. Modeling was carried out by using a 2-dimensional hydrodynamic current approach with a particle tracking module. The larval release was conducted during the full moon in the first transition period (April) and the second transition period (October). The larval source was assumed from around Sambangan waters. Modeling validation was done by comparing the model results to the direct of current measurements with Acoustic Doppler Current Profiler (ADCP). The results of larval dispersal model showed that both the transition seasons I and II were similar in the direction of movement towards the west. This result indicated that currents, tides, and winds influenced the larval dispersal process. Also, the model results showed that Sambangan, Tengah, Cilik, Sintok, the west site of Karimun, Menjangan Kecil, and Menjangan Besar Islands were identified as the location of the larval settlement.

No abstract

Lokasi geografis Teluk Lampung yang terletak di Pulau Sumatra bagian Selatan dan dipisahkan dari Pulau Jawa melalui Selat Sunda mempunyai akses langsung dengan perairan lepas dari Samudera Hindia. Hal ini akan berpengaruh terhadap pola sirkulasi arus permukaan yang terbentuk. Penelitian ini bertujuan untuk memodelkan arus permukaan di Teluk Lampung dengan menggunakan pendekatan model hidrodinamika khususnya pada musim peralihan II (Oktober – November 2020). Verifikasi model dilakukan dengan cara membandingkan hasil model arus dengan hasil pengukuran arus lapangan menggunakan currentmeter valeport yang dilaksanakan dari tanggal 12 Oktober sampai 9 November 2020. Hasil penelitian menunjukkan bahwa arus permukaan dominan dibangkitkan oleh pasang surut dengan prosentase arus pasang surut sebesar 89,09 %. Tipe pasang surut adalah tipe campuran condong harian ganda dengan nilai Formzahl 0,4. Kecepatan arus maksimum 0,168 m/s ke arah 352° dan arus minimum 0,017 ke arah 33°, sehingga arah pergerakan cenderung bolak balik. Pada kondisi pasang, arus bergerak ke utara yaitu dari Selat Sunda masuk ke perairan Teluk Lampung, dan sebaliknya pada saat surut arus bergerak ke arah selatan keluar dari perairan Teluk Lampung menuju Selat Sunda. The geographical location of Lampung Bay, which is located in the southern part of Sumatra Island and separated from Java Island by the Sunda Strait, has direct access to the waters off the Indian Ocean. This will affect the surface current circulation pattern that is formed. This research aims to model surface currents in Lampung Bay using a hydrodynamic model approach, especially in 2nd transitional monsoon (October - November 2020). Model verification is carried out by comparing the results of the current model with the results of field current measurements using a valeport current meter which was carried out from 12 October to 9 November 2020. The results showed that the dominant surface current was generated by tides with a tidal current percentage of 89.09%. The tidal type is a mixed type of mixed tide prevailing semidiurnal with a Formzahl value of 0.4. The maximum current speed is 0.168 m/s in the direction of 352° and the minimum current is 0.017 in the direction of 33°, so that the direction of movement tends to be back and forth. At high tide, the current moves northward from the Sunda Strait into the waters of Lampung Bay, and vice versa at low tide the current moves southward out of the waters of the Lampung Bay towards the Sunda Strait.