ABSTRAK
Penelitian mengenai struktur komunitas lamun di Pesisir Tanjung Luar, Kabupaten Lombok Timur, Nusa Tenggara Barat telah dilakukan pada bulan Mei 2017. Penelitian bertujuan untuk mengetahui struktur komunitas lamun yang mencakup jumlah spesies lamun, presentase tutupan, frekuensi, kerapatan, indeks nilai penting, indeks keanekaragaman, indeks kemerataan, dan indeks dominansi pada setiap stasiun. Penentuan lokasi pengambilan sampel dilakukan pada 3 stasiun penelitian dengan metode purposive sampling. Metode pengambilan sampel menggunakan metode line transect dan kuadrat sebanyak 54 kuadrat. Hasil penelitian menunjukkan bahwa terdapat tujuh spesies lamun dari dua famili di Tanjung Luar. Persentase tutupan lamun pada setiap stasiun berkisar 5--61,25. Kerapatan lamun pada setiap stasiun berkisar antara 12--626 tegakan/m2. Frekuensi setiap spesies lamun pada setiap stasiun berkisar antara 5,55--72,22. Thalassia hemprichii memiliki frekuensi rata-rata tertinggi, yaitu sebesar 50. Nilai indeks keanekaragaman di Tanjung Luar yang termasuk sedang hanya terdapat di stasiun 1 1,62 dan stasiun 2 1,69. Nilai indeks dominansi di Tanjung Luar yang tergolong rendah hanya terdapat di stasiun 2 0,21. Nilai indeks kemerataan yang tergolong tinggi hanya terdapat di stasiun 1 0,83 dan 2 0,87.

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ABSTRACT
Research on community structure of seagrass in waters of Tanjung Luar, East Lombok, West Nusa Tenggara, was conducted on May 2017. The study aims to determine the community structure of seagrass which includes diversity, cover percentage, frequency, density, importance values, diversity index, evenness index, and dominance index at all of station. The location of sampling in 3 stations was determined by purposive sampling. The method of sampling was determined by line transect and quadrat method, totally 54 quadrats. The results showed that there are 7 species of seagrasses from 2 families in Tanjung Luar. Percentage seagrass covering at each station ranged from 5 61,25. Seagrass density at each station ranged from 12 626 tegakanal m2. Frequency each spesies of seagrass at each station ranged from 5,55 72,22. Thalassia hemprichii is the highest frequency 50. The diversity index value in Tanjung Luar was considered as moderate only at station 1 1,62 and station 2 1,69. The dominance index value in Tanjung Luar was low only at station 2 0,21. Evenness index value was considered as high only at station 1 0,83 and station 2 0,87.