Kelimpahan Mikroalga Epifit Pada Daun Lamun Thalassia hemprichii dan Cymodocea rotundata Di Pulau Sintok Taman Nasional Karimunjawa

Lamun dan epifit merupakan sumber makanan penting bagi banyak organisme di laut. Organisme mikroalga epifit yang menempel pada daun lamun dapat menghalangi nutrien untuk terserap dan menurunkan produktivitas lamun. Tujuan penelitian ini mengkaji jenis - jenis mikroalga,  nilai kelimpahan, keanekaragaman, dan indeks mikroalga yang menempel di daun lamun Thalassia. hemprichii dan Cymodocea rotundata di kawasan perairan Pulau Sintok,Karimunjawa. Penelitian ini dilaksanakan pada Bulan November 2019. Lokasi penelitian dengan 3 stasiun dan masing – masing stasiun terbagi menjadi 3 sub stasiun. Metode penelitian menggunakan metode purposive sampling. Perhitungan mikroalga epifit menggunakan Sedgewick Rafter Cell. Hasil penelitian ini ditemukan 17 genus yang terdiri dari kelas Bacillariophyceae 3 genus,  Dinophyceae dan 1 genus kelas Cyanophyceae. Kelimpahan mikroalga pada daun lamun T.hemprichii yang tertinggi terdapat pada Stasiun II sebanyak 34.057,81 sel/cm2 diikuti stasiun III sebanyak 18.922,81sel/cm2 dan terendah pada Stasiun I yaitu sebanyak 17.192,98 sel/cm2. Pada daun lamun C. rotundata tertinggi pada Stasiun II sebanyak 11.988,20 sel/cm2 diikuti stasiun III yaitu 9.372,28 sel/cm2dan terendah pada Stasiun I yaitu sebanyak 8.147,39 sel/cm2. Nilai indeks keanekaragaman termasuk dalam kategori sedang, keseragaman termasuk dalam kategori tinggi dan dominansi dalam kategori rendah yang menunjukkan bahwa tidak ada spesies mikroalga dari masing – masing kelas yang mendominasi di perairan tersebut.   Seagrasses and epiphytes are important food sources for many organisms. Epiphytic microalgae organisms attached to seagrass leaves can prevent nutrients from being absorbed and reduce the productivity of the seagrass itself. If the main epiphytic predator is not present, there will be an accumulation of epiphytes on the seagrass leaves, also inhibiting its growth. The purpose of this study was to examine the types of microalgae and the abundance, diversity, and dominance values of microalgae that live on the leaf surface of Thalassia seagrass, hemprichii and Cymodocea rotundata in the waters of Sintok Island, Karimunjawa. This research was conducted in November 2019 in the waters of the island of Sintok, each of which has three stations and it’s divided into three sub-stations by purposive sampling method. Epiphytic microalgae were calculated by diluting the samples obtained to be observed under a microscope using the Sedgewick Rafter Cell. The results of this study were found as many as 17 genera of class Bacillariophyceae, three genera of Dinophyceae class and one genus of class Cyanophyceae. The highest abundance of microalgae in the leaves of seagrass T. hemprichii was found at Station II, as many as 34,057.81 cells/cm2, followed by Station III at 18,922.81 cells/cm2 and the lowest at Station I with 17,192.98 cells/cm2. Then the highest seagrass C. rotundata leaf was at Station II, as many as 11,988.20 cells/cm2, followed by Station III, which was 9,372.28 cells/cm2, and the lowest was at Station I as many as 8,147.39 cells/cm2. The diversity index value is in the medium category, uniformity is in the high category, and dominance is in a low category, indicating that no microalgae species from each class dominate in the waters.