<![CDATA[Fitoplankton mikroskopik adalah jasad renik yang melayang - layang di permukaan air. Fitoplankton merupakan tumbuhan yang banyak ditemukan di seluruh massa air pada zona eufotik, berukuran mikroskopis dan memiliki klorofil sehingga mampu membentuk zat organik dari zat anorganik melalui fotosintesis. Fitoplankton sebagai organisme autotrof menghasilkan oksigen yang akan  dimanfaatkan oleh organisme lain, sehingga fitoplankton mempunyai peranan penting dalam menunjang produktifitas perairan. Ketersedian fitoplankton suatu perairan dilihat berdasarkan kelimpahan dan klorofil ᾳ yang terjadi dalam perairan tersebut sangat ditentukan oleh keanekaragaman . Penelitian 1. Untuk mengetahui struktur komunitas fitoplankton,, klorofil α d perairan Sungai Tuntang, 2. Mengetahui indeks keanekaragaman, keseragaman dan dominasi fitoplankton di Sungai Tuntang. Penelitian dilaksanakan pada bulan Oktober 2015 di Sungai Tuntang Demak. Materi yang digunakan dalam penelitian adalah Fitoplankton dan Klorofil α . Metode yang digunakan adalah studi kasus, sedangkan pengambilannya Purposive Sampling Method. Sampling dilakukan dengan 3 kali pengulangan di 3 Stasiun lokasi sampling. Hasil penelitian didapatkan : 1. Jenis fitoplankton yang di temukan di Sungai Tuntang terdiri dari kelas Cyanophyceae, kelas Diatome, kelas Desmidiacae, kelas Chlorophyceae, dan kelimpahan fitoplankton yaitu 508 – 1261 ind/l, 2. Klorofil α berkisar antara 1,99 – 6,01 mg/m3, 3. Indeks keanekaragaman (H’) berkisar 1,72 – 2,20, indeks keseragaman (e) berkisar 0,53 – 0,69 dan indeks dominasi (c) berkisar 0,19 – 0,34.  Phytoplankton are floating microorganisms on the surface of the water. Phytoplankton is a plant that is frequently found throughout the mass of water in the euphotic zone, microscopic and has chlorophyll to be made of organic substances from inorganic substances through photosynthesis. Phytoplankton used as an autotrophic organism produces oxygen to be utilized by other organisms, so phytoplankton play an important role in supporting aquatic productivity. The existence of phytoplankton can be seen based on its abundance in waters, which is influenced by environmental parameters. This research is aimed to recognise the structure of phytoplankton community, chlorophyll existed in Tuntang waters, and to recognise the nutrient content (N, P) in Tuntang river waters. The research was conducted in October 2015 at Tuntang river, Demak. The material used in this research is Phytoplankton and Chlorophyll α. The method used in this research is descriptive method and the sampling method is Purposive Sampling Method. Sampling is done by a repeating time that is 3 times repetition at the 3 stations of the sampling location. The results showed 4 genera with 24 species dominated by Diatome such as Nitzchia sp, Thalassiosira sp. The highest abundance of phytoplankton occurred at Station 1 during the 2nd repeat of 403 ind/L dominated by Nitzchia sp. The result of measurement of α-chlorophyll content obtained showed 0.28 - 0.62 mg/l. The highest chlorophyll-α values are at station I of 0.62 and the lowest is at station II of 0.28. This shows that α-chlorophyll around the river is at a low to moderate value.]]>
