Komunitas Echinodermata di kawasan intertidal Pantai Mandalika Pulau Lombok, Indonesia - Imam Bachtiar; I Wayan Merta; Kusmiyati Kusmiyati; AR Syachruddin (Faculty of Marine and Fisheries, Universitas Syiah Kuala, 2020)
Echinoderm community was studied at the Mandalika Beach which is the main habitat of nyale worms in the southern coast of Lombok Island, from July to September 2017. The aim of study was to describe community structure of Echinoderm fauna and population structure of predominant species. Data on species richness and its abundance were collected using transect-quadrate methods. Five transects were laid haphazardly seaward that may represent the whole reef flat with about 200 m length and 100 m wide. On every 10 meter along the transect length a 5x1 m2 quadrate was made, that overall there were 44 quadrates. The results showed that only eight species of Echinoderms found in the quadrate samples, i.e. sea urchin Echinometra mathaei (Echinoidea), and brittle stars, Ophiocoma scolopendrina, O. echinata, O. erinaceus, Ophiomastix annulosa and Ophioderma sp. (Ophiuroidea). Two other Echinoidea were also found outside the quadrates, i.e. Echinothrix calamaris and Diadema setosum. Simpson diversity index (D) was 1,243, eveness index (E) was 4,023, Shanon-Winner diversity index (H) was 0,430 and equatibility index (J) was 0,267. Sea urchin E. mathaei was the most predominant population (89,38% of total composition) with average abundance 11,8722,37 individual m2. Brittle star O. scolopendrina come the second predominant population (7,31%) with average abundance 0,862,43 individual m2. The other four brittle stars had very low proportion (2%) and low abundance ( 0,20 individual m2). Population stucture showed that these two populations mostly consisted of reproductive members. Ecological interactions of these two predominant Echinoderms should be studied in more detail on interactions among of the Echinoderms and nyale worms.Keywords:Ophiocoma,Echinometra,Nyale,Lombok Tengah,population structureABSTRAKPenelitian komunitas Echinodermata dilakukan di Pantai Mandalika yang menjadi habitat utama cacing nyale, pada bulan Juli-September 2017. Penelitian ini bertujuan mendeskripsikan struktur komunitas Echinodermata dan struktur populasi spesies yang dominan. Data kekayaan spesies dan kelimpahan diambil dengan metode transek kuadrat. Lima transek diletakkan tersebar ke arah laut pada pantai yang panjangnya sekitar 200 m dan lebar 100 m tersebut. Setiap titik 10 meter pada transek dibuat kuadrat ukuran 5 m2, dengan jumlah kuadrat sampel seluruhnya 44 kuadrat. Hasil penelitian menunjukkan bahwa komunitas Echinodermata mempunyai kekayaan spesies yang rendah di Pantai Mandalika. Organisme Echinodermata yang dijumpai hanya 8 (delapan) spesies, yaitu landak laut Echinometra mathaei (Echinoidea), serta lima jenis bintang mengular, Ophiocoma scolopendrina, O. echinata, O. erinaceus, Ophiomastix annulosa dan Ophioderma sp. (Ophiuroidea). Di luar kuadrat tercatat dua jenis landak laut lainnya, yaitu Echinothrix calamaris dan Diadema setosum, dengan kelimpahan yang sangat rendah. Indeks-indeks komunitas pada umumnya rendah. Indeks diversitas Simpson (D) 1,243, indeks keseragaman (E) 4,023, indeks keanekaragaman spesies Shanon-Winner (H) 0,430 dan indeks kesetaraan (J) 0,267. Landak laut E. mathaei sangat dominan (89,38%) dengan kelimpahan rata-rata 11,8722,37 individu m-2 di dalam komposisi komunitas Echinodermata. Bintang mengular O. scolopendrina menempati urutan dominansi kedua (7,31%) dengan kelimpahan rata-rata 0,862,43 individu m-2, sedangkan empat bintang mengular lainnya mempunyai proporsi kurang dari 2% dan kelimpahan rata-rata kurang dari 0,20 individu m-2. Struktur populasi E. mathaei dan O. scolopendrina menunjukkan bahwa sebagian besar anggota populasi mempunyai ukuran reproduktif. Kehadiran hewan Echinodermata tersebut di habitat cacing nyale (Eunicidae, Polychaeta) menuntut penelitian lanjutan tentang peran ekologis dari masing-masing hewan Echinodermata dan interaksinya dengan cacing nyale.Kata kunci:Ophiocoma,Echinometra,Nyale,Lombok Tengah, Struktur populasi