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Abstrak :
Telah dilakukan penelitian tentang struktur populasi kerang Pinna muricata dan korelasinya dengan kepadatan lamun di sekitarnya. Tujuan dari penelitian ini adalah untuk membandingkan dan menganalisis struktur populasi kerang Pinna muricata yang meliputi kelimpahan, persebaran, dan ukuran, serta mencari tahu ada atau tidaknya korelasi dengan jumlah lamun di sekitarnya. Penelitian dilakukan dengan menggunakan transek sepanjang 50 meter yang dibentangkan mengelilingi pulau secara tegak lurus dari pantai. Pada jalur transek tersebut diletakan kuadrat dengan luas 10×2 m2 sebanyak tiga buah dengan jarak antar kuadrat adalah 10 m. Pinna muricata yang ditemukan pada tiap kuadrat dihitung dan diletakan kuadrat kecil seluas 1×1 m2 dengan posisi sehingga Pinna muricata berada di tengah kuadrat tersebut. Tegakkan tiap jenis lamun yang ada dalam kuadrat kecil dihitung. Setelah itu, cangkang kerang diambil dari substrat dan dihitung morfometrinya menggunakan penggaris. Tiap data yang didapat ditampilkan dalam tabel, dan dibandingkan dengan data yang didapat pada penelitian sebelumnya. Data jumlah Pinna muricata, jumlah tegakkan lamun, dan panjang total cangkang diuji dalam rumus Uji Korelasi Spearman. Hasil menunjukkan bahwa jumlah kerang Pinna muricata menurun sampai 42,6%, dan panjang total cangkang dari Pinna muricata menurun 13,49% dibandingkan dengan penelitian pada tahun 2003. Hasil Uji Korelasi Spearman menunjukan adanya nilai korelasi positif antara jumlah Pinna muricata dan jumlah tegakkan lamun dengan nilai koefisien korelasi 0,86, namun, ditemukan nilai korelasi negatif antara panjang total cangkang Pinna muricata dengan jumlah tegakkan lamun dengan nilai koefisien korelasi -0,51. ......A research about the population structure of Pinna muricata and its correlation with the number of seagrass shoots around them had been conducted. The purpose of this study was to count, compare, and analyze the population structure of Pinna muricata in the shape of their numbers, distributions, and size, then finding out whether or not those factors have any correlations with the number of seagrass’ shoots around them. Data collecting was done with a 50 meter line transect placed vertically with shoreline. On the transect track, a 10×2 m2 quadrats was placed three times, with the distance of each quadrats is 10 m. Each Pinna muricata that was found on the quadrat was counted, and then a smaller quadrat with the size of 1×1 m2 was put in a way that makes the Pinna muricata is placed on the center of the small quadrat. Every seagrass’ shoots that was found on the small quadrat was counted. Then Pinna muricata was picked from its substrate to measure its morphometrics. Every data that was found was displayed on a table to be compared with previous research. The number of Pinna muricata that was found, number of seagrass’ shoots, and the total length of Pinna muricata was analyzed using the Spearman’s Rank Correlation Coefficient formula. Results show that the number of Pinna muricata had decrease by 42,6%, and the total length of Pinna muricata had also decrease by 13,49% when compared to a previous study in 2003. The results of Spearman’s rank correlation coefficient showed a positive correlation between the number of Pinna muricata and the number of seagrass’ shoots, with the number of correlation coefficient is 0,86. The result also showed a negative correlation between the total length of Pinna muricata’s shell and the number of seagrass’ shoots, with the number of correlation coefficient is -0,51.

Abstrak :
Telah dilakukan penelitian ekologi Pinna muricata yang mencakup kepadatan, morfometri cangkang, sudut posisi kedudukannya lerhadap garis pantai, serta hubungannya dengan kepadalan dan biomassa lamun Cymodocea rotundata di Pulau Semak Daun, Kepulauan Seribu, Teluk Jakarta. Hasil penelitian menunjukkan Pinna muricata hanya ditemukan di antara lamun Cymodocea rotundata di 6 transek dari 16 transek yang digunakan, 4 transek (transek 7- 10) di bagian Selatan dan 2 transek (transek 12 dan lj) di bagian Utara. Kepadatan terbanyak terdapat di bagian Selatan pulau (0,6 individu per m3}, sedangkan di bagian Utara puiau kepadalannya hanya mencapai 0,03 individu per m2. Pinna muricata mempunyai panjang cangkang yang berkisar antara 12,5 - 17 cm dengan rata-rata 14,25 cm, sedangkan lebar cangkang berkisar antara 7 - 11,4 cm dengan rata-rata 8,43 cm. Sudut kedudukan Pinna muricata terbanyak (17%) antara 130" - 139° terhadap garis pantai. Kepadalan dan biomassa akar lamun Cymodocea roiundata tidak berkorelasi atau tidak ada hubungannya dengan jumlah Pinna muricata, sedangkan bkimassa daun menunjukkan korelasi negative (R= -0,36).

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We examined fan mussel Pinna muricata (Mollusca, Bivalvia) such as the density, shell morphomeiry, angel of shell position against the shoreline, as well as his correlations with the density and the biomass of seagrass Cymodocea rotundata in the Semak Daun Island, Jakarta Bay. Results of Ihe research pointed out Pinna muricata were found only in seagrass meadows Cymodocea rotundata in 6 transects from 16 transects lhat was used, 4 transects (transect 7 - 10) on the South and 2 transects (transect 12 and 13) at the North of Island. The Pinna density was recorded 0.6 individuals per m2 at the southern of the island, whereas at the northern of the island only reached 0.03 individuals per m2. The length and wide of shells were measured between 12,5 - 17 cm (average 14,25 cm) and between 7 ? 11,4 cm (average 8,43 cm) respectively. The most angle of shell positions were measured between 120° - 139" against the shoreline. The density and the leave biomass seagrass Cymodocea rotundata did not correlate with the density of Pinna, whereas the root biomass have negative correlation (R= - 0,36).