Plankton berperan penting dalam ekosistem perairan sebagai pakan alami bagi berbagai organisme yang kelimpahannya dipengaruhi oleh kualitas air. Penelitian ini bertujuan menganalisis hubungan kualitas air dengan struktur komunitas plankton di tambak tradisional Kabupaten Tana Tidung, Kalimantan Utara. Pengambilan sampel dilakukan pada tiga stasiun, yaitu Desa Sambungan, Desa Tanah Merah dan Desa Bebatu. Parameter abiotik yang diamati meliputi suhu, pH, salinitas, DO, nitrat, dan fosfat. Parameter biotik mencakup kelimpahan, keanekaragaman (H'), keseragaman (E), dan dominansi plankton. Hasil menunjukkan kelimpahan tertinggi terdapat di Stasiun 3 dengan fitoplankton 360 sel/L dan zooplankton 5 ind/L, sedangkan kelimpahan terendah di Stasiun 2 (fitoplankton 250 sel/L; zooplankton 3 ind/L) dan Stasiun 1 (fitoplankton 163 sel/L; zooplankton 5 ind/L). Indeks keanekaragaman di Stasiun 1 (fitoplankton 1,121; zooplankton 1,442) dan Stasiun 2 (fitoplankton 1,108; zooplankton 1,009) tergolong sedang, sedangkan di Stasiun 3 lebih rendah (fitoplankton 0,993; zooplankton 0,714). Analisis regresi menunjukkan bahwa kelimpahan fitoplankton sangat dipengaruhi oleh nitrat (R² = 99,9%), salinitas (R² = 93,5%), suhu (R² = 80,5%), dan fosfat (R² = 77,2%). Zooplankton dipengaruhi oleh DO (R² = 93,4%) dan suhu (R² = 84,2%). Kualitas air terbukti memengaruhi struktur komunitas plankton secara signifikan. Analisis menunjukkan bahwa kelimpahan fitoplankton dan zooplankton dipengaruhi oleh berbagai parameter kualitas air, terutama nutrien, suhu, salinitas, dan oksigen terlarut. Setiap jenis plankton merespons faktor lingkungan secara berbeda, sehingga kualitas air berperan penting dalam membentuk struktur komunitas plankton. Temuan ini menekankan pentingnya pemantauan kualitas air demi menjaga keseimbangan ekosistem tambak.
Kata Kunci: Biomonitoring, Ekosistem Tambak, Oligotrofik, Produktivitas primer

Plankton play a crucial role in aquatic ecosystems as a natural food source for various organisms, with their abundance influenced by water quality. This study aims to analyze the relationship between water quality and plankton community structure in traditional aquaculture ponds in Tana Tidung Regency, North Kalimantan. Sampling was conducted at three stations: Sambungan Village, Tanah Merah Village, and Bebatu Village. The observed abiotic parameters included temperature, pH, salinity, dissolved oxygen (DO), nitrate, and phosphate. The biotic parameters encompassed plankton abundance, diversity index (H'), evenness (E), and dominance. Results indicated the highest abundance at Station 3, with phytoplankton at 360 cells/L and zooplankton at 5 individuals/L, while the lowest abundance was recorded at Station 2 (phytoplankton: 250 cells/L; zooplankton: 3 ind/L) and Station 1 (phytoplankton: 163 cells/L; zooplankton: 5 ind/L). Diversity indices at Station 1 (phytoplankton: 1.121; zooplankton: 1.442) and Station 2 (phytoplankton: 1.108; zooplankton: 1.009) were categorized as moderate, whereas Station 3 showed lower diversity (phytoplankton: 0.993; zooplankton: 0.714). Regression analysis revealed that phytoplankton abundance was strongly influenced by nitrate (R2=99.9%), salinity (R2=93.5%), temperature (R2=80.5%), and phosphate (R2 = 77.2%). Zooplankton abundance was affected by DO (R2 = 93.4%) and temperature (R2 = 84.2%). The results demonstrate that water quality significantly influences the plankton community structure. The analysis highlights that both phytoplankton and zooplankton abundances are shaped by various water quality parameters, particularly nutrients, temperature, salinity, and dissolved oxygen. Different plankton groups respond uniquely to environmental factors, emphasizing the critical role of water quality in shaping plankton community structure. These findings underscore the importance of continuous water quality monitoring to maintain ecological balance in aquaculture pond systems. Biomonitoring, Aquaculture Ecosystem, Oligotrophic, Primary Productivity