Produktivitas rumput laut di kota tarakan sangat dipengaruhi oleh kualitas bibit kappaphycus alvarezii, kemampuan rumput laut bertahan terhadap pathogenesis tergantung kualitas bibit. tujuan dari penelitian ini untuk menghitung jumlah koloni bakteri yang terdapat pada talus rumput laut kappaphycus alvarezii serta pada media pemeliharaannya di air. bakteri pada sampel rumput laut dihitung menggunakan metode total plate count (tpc), hasil perhitungan didapatkan kepadatan koloni bakteri secara berurutan minggu kedua 83x102 cfu/ml (k2) yang terendah sampai 10x106 cfu/ml (t2) yang tertinggi, minggu ketiga 16x102 cfu/ml (k2) yang terendah sampai yang tertinggi 63x103 cfu/ml (l2), minggu keempat 500 cfu/ml (k3) yang terendah sampai yang tertinggi 780 cfu/ml (k2). berdasarkan analisis morfologi koloni yaitu terdapat bentuk circular,irregular, terdapat warna putih kepucatan dan kuning diakhir penelitian, serta elevasi flat, sedangkan pada media air pemeliharaan inkubasi yang dilakukan belum berhasil menumbuhkan koloni bakteri hal tersebut diduga bak wadah pemeliharaan sudah steril secara fisika. kata kunci: kappaphycus alvarezii, koloni bakteri, tpc

Seaweed productivity in tarakan city is strongly influenced by the quality of kappaphycus alvarezii seeds, the ability of seaweed to survive pathogenesis depends on seed quality. the purpose of this study was to calculate the number of bacterial colonies found in the thallus of kappaphycus alvarezii seaweed and its maintenance media in water. bacteria in seaweed samples were counted using the total plate count (tpc) method, the results of the calculation showed that the density of bacterial colonies in the second week was 83x102 cfu/ml (k2), the lowest to 10x106 cfu/ml (t2). the highest, the third week was 16x102 cfu/ ml (k2) the lowest to the highest 63x103 cfu/ml (l2). the fourth week 500 cfu/ml (k3) the lowest to the highest 780 cfu/ml (k2). based on the morphological analysis of the colonies, there were circular, irregular shapes, there were, pale white and yellow colors at the end of the study, as well as flat elevations, although the water medium for incubation and maintenance failed to establish bacterial colonies, it was assumed that container used for rearing the organisms was physically sterile. keywords: kappaphycus alvarezii, bacterial colonies, tpc