REPRODUKSI KARANG Poollopora darnicornis (Linnaeus) DI PULAU PANJANG, JAWA TENGAH

Abstract

Penelitian ini bertujuan untuk mengetahui masa reproduksi, kemampuan reproduksi dan laju rekrutmen karang P. damicornis di sisi selatan dan sisi utara Pulau Panjang, Jawa Tengah. Masa reproduksi karang diketahui dari pengamatan gametogenesis, embriogenesis dan pelepasan larva (planulasi). Kemampuan reproduksi karang diukur dari fekunditas polip dan produksi larva setiap koloni sedangkan laju rekrutmen ditentukan dengan menghitung kerapatan juvenil yang menempel pada substrat penempelan. Hasil menunjukkan bahwa kemampuan reproduksi dan laju rekrutmen karang P. damicornis antara sisi selatan dan sisi utara P. Panjang berbeda. Masa reproduksi tidak menunjukkan perbedaan dan terjadi setiap bulan sepanjang tahun. Masa planulasi karang terjadi dad bulan baru hingga bulan purnama dengan kematangan garnet terjadi pada bulan purnama dan bulan 3/4, hal ini menunjukkan bahwa planulasi ditentukan oleh siklus gametogenesis dan dipengaruhi oleh interaksi pasang surut dan lunar. Siklus gametogenesis berganda tersebut telah mempengaruhi terjadinya dua puncak planulasi pada koloni tunggal sedangkan planulasi pada koloni berpasangan hanya terjadi dalam satu puncak, hal ini mengindikasikan bahwa variasi masa planulasi ditentukan oleh adaptasi siklus gametogenesis akibat keberadaan koloni lain. Reproduksi karang sepanjang tahun bervariasi secara musiman, meningkat pada musim Timur dan menurun pada musim Barat yang dipengaruhi oleh interaksi fotoperiode (panjang hari), suhu perairan, nutrien dan curah hujan. Perbedaan kemampuan reproduksi antar lokasi disebabkan oleh frekuensi dan tinggi gelombang, sehingga produksi larva di sisi utara lebih rendah daripada sisi selatan. Tingginya produksi larva di sisi selatan dan terdapatnya arus pusaran mengakibatkan tingginya rekrutmen di sisi selatan namun kelulusan hidup juvenilnya rendah. Rekrutmen ditandai oleh tingginya kematian juvenil pada awal penempelan dan tingginya kemelimpahan juvenil di sisi bawah permukaan substrat akibat endapan. Tingginya rekrutmen di sekitar induknya mencerminkan sebaran koloni dewasanya. Hasil ini mengisyaratkan bahwa rekrutmen karang P. damicornis di P. Panjang bersifat internal. Kata-kata kunci : reproduksi, planulasi, rekrutmen, karang Pocillopora damicornis, Pulau Panjang Jawa Tengah This study was designed to investigate the reproduction period, reproductive effort and recruitment rate of coral Pocillopora damicornis in southern and northern sides of Panjang Island, Central Java. Reproduction period was determined by observing gametogenesis, embryogenesis and planulation (planulae release) period, while the reproductive effort was estimated by measuring polyp fecundity and larval production in each colony. Recruitment rate of the coral was determined by the density of juvenile in the field. The results showed that reproductive effort and recruitment rate of coral P. damicornis between southern and northern sides of Panjang Island was different. Reproduction period was not different between the sides while reproductive activities occurs every month throughout the year. Planulation occurred from new moon to full moon with gamete maturation in full moon and third quarter moon, indicated that planulation was controlled by gametogenesis cycle and infulenced by the interaction between tide and lunar. The multiple gametogenic cycles resulted double peaks planulation in a single colony while planulation in paired colony revealed single peak, indicated that variation in planulation period due to adaptation of gametogenic cycles which controlled by the existence of other colonies. Reproductive effort varied seasonally with increasing the polyp fecundity and larval production in southeast monsoon and decreasing in northwest monsoon. The annual fluctuations in reproduction was controlled by the interaction of water temperature, fotoperiod (day length), nutrien, and rainfall. Reproductive effort was different between southern and northern sides probably in response to reduced number of productive polyp in northern side which influenced by high wave frequency and wave height. High larval production in southern side and which trapped by the turbulent eddies current caused high recruitment in the side however the side revealed low in survival rate of juvenile. Recruitment was characterized by high mortality of juvenile in the early settlement period and high abundance of juvenile under surfaces of settlement plates which influenced by sediment accumulation. High recruitment occurred around their parental colonies seems to corresponding with the adult distribution. It is suggested that coral P. damicornis maintained the population by internal recruitment. Key words : reproduction, planulation, recruitment, coral Pocillopora damicornis, Panjang Island Central Java