STUDI EKOLOGI REPRODUKSI KARANG CABANG ACROPORA ASPERA UNTUK MENGATASI KONDISI KRITIS EKOSISTEM TERUMBU KARANG

Widjatmoko, Wisnu and Munasik, Munasik (2003) STUDI EKOLOGI REPRODUKSI KARANG CABANG ACROPORA ASPERA UNTUK MENGATASI KONDISI KRITIS EKOSISTEM TERUMBU KARANG. Documentation. Fakultas Perikanan dan Ilmu Kelautan.

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Abstract

Terumbu karang merupakan salah satu sistem pendukung kehidupan terpenting dunia yang berfungsi sebagai penyedia makanan, kesehatan dan aspek-aspek yang berkaitan dengan kelangsungan kehidupan manusia dan pembangunan yang berkelanjutan. Namun, masa depannya telah dihambat oleh kegiatan eksploitasi berlebih (over exploitation), dampak kegiatan anthropogenic, polusi sedimen dari lahan atas dan perubahan iklim global (global climate change). Kondisi terumbu karang di Indonesia yang masih sangat balk hanya sekitar 6%. Untuk pelestariannya membutuhkan pengelolaan yang berkelanjutan. Salah satu aspek penting dalam pengelolaan dan konservasi ekosistem terumbu karang adalah ketersediaan informasi mengenai bio-ekologi reproduksi karang. Hewan karang (Scleractinia) merupakan organisme penyusun utama ekosistem terumbu • karang. Karang bercabang Acropora adalah jenis karang penyusun terumbu karang yang paling penting di Indonesia, karena di wilayah ini memiliki keanekaragaman jenis Acropora tertinggi di dunia (tercatat 91 spesies). Namun studi mengenai jenis karang ini di Indonesia sangat kurang terutama aspek biologi reproduksi karang. Studi ekologi reproduksi karang Acropora aspera telah dilakukan di Pulau Panjang Jepara (6° 34' 30" LS 110° 37' 45" BT) pada bulan 3 Oktober 2001 - 28 April 2002 mela;ui pengamatan visual dan irisan histologi. Jenis karang bercabang ini ditemukan mulai kedalaman 40 cm hingga 400 cm dengan Densitas koloni dari 0,12 - 3 koloni/m2 dan densitas rata-rata koloni 0,93 koloni/m2. Karang A. aspera tergolong berjenis kelamin hermaphrodhite, memiliki oVarium dan testis dalam satu polip. Oogenesis berlangsung lebih dari satu siklus dalam setahun. Oosit matang dan belum matang ditemukan pada Oktober 2001 dan dari Januari 2002 hingga April 2002. Sebaliknya pada Nopember-Desember 2001 dan Mei 2002 tidak ditemukan oosit dalam polip karang. Spermatogenesis berlangsung lebih lama Januari-April 2002, spermatozoa yang slap untuk dilepaskan terdapat di bulan April 2002. Karang bercabang Acropora aspera melakukan spawning di aquarium secara serentak dan ekstensif terjadi pada 5 April 2002 bertepatan dengan kalender lunar 22 Sura (bulan 1/4). Sedangkan koloni lainnya spawning secara terpisah pada 20 April dan 24 April bertepatan path kalender lunar bulan 3/4 dan 4 hari sebelum purnama. Saat spawning dimulai jam 20.00 hingga 23.00, dua jam setelah matahari tenggelam (sunset). Garnet-garnet hasil spawning yang berhasil melakukan fertilisasi eksternal ini sangat rendah. Hanya beberapa garnet yang berhasil membentuk embryo awal hingga fase 32 set. Strategi reproduksi seksual karang cabang A. aspera ditunjukkan dengan trik spawning berulang dan terjadi tidak serentak balk antar cabang koloni maupun koloni karang. Spawning ditentukan oleh siklus kematangan gonad jantan (spermatogenesis), diduga oleh karena siklus spermatogenesis terjadi 2 kali dalam setahun, maka spawning terjadi dua kali dalam setahun. Memperhatikan distribusi populasi koloni karang dan rendahnya kemampuan fertilisasi telur-telur karang, diduga recruitment karang A. aspera di dataran terumbu Pulau Panjang lebih banyak dilakukan dengan cara reproduksi tak kawin (aseksual) melalui fragmentasi. Coral reefs are one of the essential global life support systems necessary for food production, health and other aspects of human survival and sustainable development. However, their future is being threatened by overexploitation, coastal development, land-based pollution and moreover, by global climate change. In 1991, the Indonesian coral reefs were classified as critical, meaning that if the current trends in overexploitation and mismanagement continue unchecked, the majority of coral reefs in Indonesia will be lost in 10-20 years. Recent survey indicated that only about 6% of the Indonesian reefs is still in excellent condition and the rest are in various stages of destruction. Coral reef management and conservation issues in Indonesia are complex, and vary from region to region. While the area extent coral reefs in Indonesian archipelago, as for the rest of the world, cannot be stated with great precision. Management plans for the conservation of coral reefs can be greatly enhanced by accurate information regarding the species composition, distribution of taxa within and between different geographical regions, moreover information on corals reproduction. The Indonesian archipelago contains the greatest recorded diversity for Acropora, 91 species, Acropora plays a dominant role in the species composition and abundance of many modern day Indonesian reefs. However, detailed information on their reproduction in Indonesia is rare. Reproductive ecology of A, aspera at Panjang Island, lepara -Java Sea (6° 34' 30" LS 110° 37' 45" BT) was studied by field observations of coral population, histology and laboratory observations of coral spawning from 3 Oktober 2001 - 28 April 2002. The coral was distributed in reef flat from 40-400 cm depth and density of colony vary from 0,12 - 3 colony/m2. Coral A. aspera is hermaphroditic spawner, their oocytes were visible in October- 2001 and January-April 2002 on histological sections, while spermatogenesis occurred from January to April 2002. During this observation period, spermatozoa first appeared in March 2002, while both mature and immature oocytes first appeared in January and were continually produced until April 2002. Gametes were spawned simultaneously on 5 April 2002 In first quarter moon. While other colonies spawned gametes on 20 April and 24 April in third quarter moon and 4 days before full moon. Spawning occurred at 2.00-23.00, 2 hours after sunset. Only several gametes that were fertilized to developed a larva. First cleavage occurred at 2-3 hour after spawning. Synchronous division occurred in the first cleavage and produced two equal blastomeres, while asynchronous division occurred after forming embryo ca. 16 cells. Reproductive plasticity in corals has been considered to occur in corals on reef flats, where physical environment is usually harsh. The present study suggested that the shallow water A. aspera show asynchronously multiple spawning events, while no sign of external fertilization was occurred. Thus, Acropora aspera may recruit successfully not by sexual reproduction but by asexual reproduction i.e. fragmentations.

Item Type:Monograph (Documentation)
Subjects:S Agriculture > SH Aquaculture. Fisheries. Angling
Divisions:Faculty of Fisheries and Marine Sciences > Department of Marine Science
ID Code:21691
Deposited By:Ms upt perpus3
Deposited On:02 Sep 2010 13:14
Last Modified:02 Sep 2010 13:14

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