Keberadaan unsur hara dan plankton pada tambak tradisional menjadi parameter kesuburan perairan. Penelitian ini bertujuan untuk menganalisis fluktuasi konsentrasi unsur hara dalam air dan sedimen tambak serta struktur komunitas plankton di tambak tradisional Kota Tarakan. Penelitian dilakukan pada bulan September-November 2023 pada tambak udang windu di Kecamatan Tarakan Barat Kota Tarakan. Metode penelitian yang digunakan adalah metode kualitatif dan kuantitatif. Analisis data mengacu pada Permen KP. No. 75 Tahun 2016, Permen Pekerjaan Umum dan Perumahan Rakyat No. 21 tahun 2015, dan perhitungan kelimpahan, keanekaragaman, keseragaman, dan dominansi plankton. Hasil penelitian menunjukkan bahwa suhu air berkisar antara 20-29°C, dengan rata-rata 24,8±3,3°C, yang lebih rendah dibandingkan baku mutu menurut Peraturan Menteri Kelautan dan Perikanan Permen KP. No. 75 Tahun 2016 (28-32°C). Salinitas tertinggi tercatat pada minggu pertama (25 ppt) dan masih berada dalam kisaran standar (5-40 ppt). Nilai pH air berkisar antara 7,28-8,08, sesuai dengan baku mutu (7,5-8,5). Kadar oksigen terlarut mencapai nilai tertinggi 8,1 mg/L pada minggu ke 4 dan berada di atas batas minimal yang direkomendasikan ( > 3 mg/L). Kadar amonia tertinggi tercatat sebesar 1,67 mg/L, melebihi ambang batas yang direkomendasikan ( < 0,01 mg/L). Konsentrasi nitrat relatif stabil dalam kisaran 0,08-0,09 mg/L, masih di bawah baku mutu < 0,5 mg/L. Konsentrasi fosfat di air mengalami fluktuasi dan sebagian besar waktu berada di bawah nilai standar minimal yang direkomendasikan (0,1 mg/L). Analisis komunitas plankton menunjukkan variasi jenis dan kelimpahan yang dipengaruhi oleh faktor lingkungan. Kelimpahan fitoplankton tertinggi tercatat 3 sel/L pada minggu ke 2, sementara zooplankton tertinggi mencapai 8 sel/L pada minggu ke 3. Nilai indeks keanekaragaman plankton tertinggi sebesar 1,099 menunjukkan komunitas yang cukup stabil. Kualitas air tambak masih berada dalam kisaran optimal untuk budidaya udang windu, namun fluktuasi kandungan amonia dan rendahnya kandungan fosfat perlu diperhatikan untuk mendukung keberlanjutan budidaya.
Kata Kunci: Air, baku mutu, sedimen

The presence of nutrients and plankton in traditional ponds is a parameter of water fertility. This study aimed to analyze the fluctuation of nutrient concentrations in water and pond sediments and plankton communities' structure in traditional Tarakan ponds. The study was conducted in September-November 2023 in tiger shrimp ponds in West Tarakan District, Tarakan. The research methods used are qualitative and quantitative. Data analysis refers to the Regulation of the Minister of Marine Affairs and Fisheries No. 75 of 2016, the Minister of Public Works and Public Housing No. 21 of 2015, and the calculation of plankton's abundance, diversity, uniformity, and dominance. The results showed that the water temperature ranged from 20-29°C, with an average of 24.8±3.3°C, which is lower than the quality standard according to the Regulation of the Minister of Marine Affairs and Fisheries Permen KP. No. 75 of 2016 (28-32°C). The highest salinity was recorded in the first week (25 ppt) and was still within the standard range (5- 40 ppt). The pH value of the water ranged from 7.28-8.08 by the quality standard (7.5-8.5). The dissolved oxygen level reached the highest value of 8.1 mg/L in the fourth week and was above the recommended minimum limit ( > 3 mg/L). The highest ammonia level was recorded at 1.67 mg/L, exceeding the recommended threshold ( < 0.01 mg/L). The nitrate concentration was relatively stable in the 0.08- 0.09 mg/L range, still below the quality standard < 0.5 mg/L. Phosphate concentration in water fluctuates and, most of the time is below the recommended minimum standard value (0.1 mg/L). Plankton community analysis shows variations in types and abundance influenced by environmental factors. The highest phytoplankton abundance was recorded at 3 cells/L in week 2, while the highest zooplankton reached 8 cells/L in week 3. The highest plankton diversity index value of 1.099 indicates a fairly stable community. The pond water quality is still within the optimal range for tiger shrimp cultivation. However, fluctuations in ammonia and low phosphate content need to be considered to support sustainable cultivation. Keywords: Water, quality standards, sediment