Muara Sungai merupakan perairan semi tertutup yang terletak di bagian hilir sungai dan masih berhubungan dengan laut sehingga memungkinkan untuk terjadinya pencampuran dua massa air, yakni air tawar dan air laut. Tujuan penelitian untuk mengetahui komposisi dan kelimpahan larva ikan, mengetahui perbedaan struktur komunitas pada saat pasang dan surut. Metode yang di gunakan adalah metode survei yang dilaksanakan pada bulan Mei 2018 di Muara sungai Morosari Sayung, Demak. Sampling dilakukan pada 3 stasiun dengan kondisi pasang dan surut. Variabel yang diukur antara lain Komposisi, Kelimpahan Larva ikan dan Struktur komunitas pada saat pasang dan surut. Hasil penelitian didapatkan Larva ikan pada saat pasang di stasiun I sebanyak 43 ind, stasiun II diperoleh larva ikan sebanyak 22 ind dan stasiun III sebanyak 34 ind. Hasil penelitian didapatkan pada saat surut di stasiun I sebanyak 24 ind, stasiun II 22 ind dan stasiun III sebanyak 34 ind. Keseluruhan larva ikan yang tertangkap terdiri dari 10 famili yaitu Nemipteridae, Mugilidae, Gobiidae, Ambassidae, Acrididae, Chanidae, Engraulidae, Labridae, Scatophagidae dan Lactaridae. Indeks keanekaragaman pada saat pasang termasuk dalam kategori rendah dan sedang dengan nilai berkisar 0,99-1,6. Indeks keseragaman berkisar antara 0,78-0,91 maka tergolong kedalam kategori tinggi atau stabil. Nilai indeks Dominasi termasuk kedalam dominasi rendah dan sedang dengan nilai berkisar antara 0,22-0,40. Nilai indeks keanekaeragaman pada saat surut masuk dalam kategori rendah dan sedang dengan nilai berkisar 0,91-1,41. Indeks keseragaman berkisar 0,66-0,91 masuk dalam kategori stabil. Dominasi berkisar antara 0,32-0,45, dengan nilai tersebut maka dapat dikategorikan Dominasi sedang. Estuary is a semi-closed waters located in the downstream part of the river and still in contact with the sea, allowing for mixing of two water masses, namely fresh water and sea water. The purpose of this research is to find out the composition and abundance of fish larvae, to know the differences in community structure during high and low tide levels. The method used in this research is a survey method conducted in May 2018 in the river estuary of Morosari Sayung, Demak. Sampling was carried out at 3 tidal and low tide stations. Variables measured include Composition and Abundance of fish larvae and community structures during highs and low tide level. The research result showed that 43 ind larvae at high tide at station I, were 22 ind at stations II, were obtained and 34 ind stations III. The results of the research were obtained at low tide at station I as many as 24 ind, station II 22 ind and station III as many as 34 ind. All captured fish larvae consist of 10 families namely Nemipteridae, Mugilidae, Gobiidae, Ambassidae, Acrididae, Chanidae, Engraulidae, Labridae, Scatophagidae and Lactaridae. The diversity index value at the high tide entered in the low and medium category ranged from 0.99 to 1.6. Uniformity lindex ranges from 0.78 to 0.91 in the medium category. Domination ranges from 0.22 to 0.40, with this value the entire research station into the category there is no dominance. The diversity index value at the low tide entered in the low and medium category ranged from 0.91 to 1.41. The uniformity index ranges from 0.66 to 0.91 included in the stable category. Domination ranges from 0.32-0.45 with this value can be categorized medium.
The diversity of plankton as bioindicators in Kakap River Estuary, West Kalimantan