Perairan tambak merupakan salah satu ekosistem buatan yang memiliki peran penting dalam mendukung kegiatan budidaya perikanan. Penelitian ini bertujuan untuk mengetahui struktur komunitas gastropoda serta hubungan antara komposisi substrat dan kualitas air terhadap kelimpahan dan keanekaragaman jenisnya di tambak tradisional Kota Tarakan, Kalimantan Utara. Penelitian dilaksanakan pada bulan Januari hingga Maret 2025 menggunakan metode deskriptif dengan pendekatan kuantitatif. Penentuan stasiun dan titik sampling dilakukan secara purposive sampling berdasarkan karakteristik vegetasi, substrat, serta aktivitas manusia di sekitar lokasi. Pengambilan sampel gastropoda dan sedimen dilakukan di tiga stasiun penelitian, masing-masing dengan lima titik pengamatan (plot 1x1 meter), serta pengukuran parameter fisik-kimia perairan (suhu, salinitas, pH, dan oksigen terlarut). Identifikasi spesies gastropoda dilakukan secara morfologis di laboratorium. Hasil penelitian menunjukkan terdapat enam spesies gastropoda yang tergolong dalam dua famili, yaitu Potamididae dan Neritidae, dengan Pirenella alata sebagai spesies paling dominan. Nilai indeks keanekaragaman tertinggi terdapat di stasiun 1 sebesar H' = 1,31 yang tergolong keanekaragaman sedang, sedangkan stasiun 2 dan 3 memiliki nilai H' masing-masing 0,51 dan 0,52 yang tergolong keanekaragaman rendah. Indeks dominansi menunjukkan dominansi rendah di stasiun 1 (C = 0,36) dan dominansi tinggi di stasiun 2 dan 3 (C = 0,68 dan C = 0,74). Indeks keseragaman menunjukkan nilai stabil di stasiun 1 dan 2, namun rendah di stasiun 3. Faktor lingkungan seperti suhu, pH, dan DO berada dalam kisaran optimal untuk kehidupan gastropoda, sedangkan salinitas menunjukkan fluktuasi ekstrem yang diduga kuat memengaruhi distribusi dan keberagaman spesies. Temuan ini menunjukkan pentingnya pengelolaan kualitas lingkungan tambak dan penggunaan gastropoda sebagai indikator biologis dalam evaluasi kondisi ekosistem perairan.
Kata Kunci: Gastropoda, Keanekaragaman, Kualitas Air, Substrat, Tarakan

Pond waters are one of the artificial ecosystems that play a crucial role in supporting aquaculture activities. This study aims to determine the structure of the gastropod community and the relationship between substrate composition and water quality on the abundance and diversity of gastropod species in the traditional ponds of Tarakan City, North Kalimantan. The research was conducted from January to March 2025 using a descriptive method with a quantitative approach. Station and sampling point selection was conducted using purposive sampling based on vegetation characteristics, substrate, and human activities around the location. Gastropod and sediment samples were collected at three research stations, each with five observation points (1x1-meter plots), along with measurements of water physical-chemical parameters (temperature, salinity, pH, and dissolved oxygen). Gastropod species identification was conducted morphologically in the laboratory. The results showed six gastropod species belonging to two families, Potamididae and Neritidae, with Pirenella alata as the most dominant species. The highest diversity index value was found at station 1, with h' = 1.31, classified as moderate diversity, while stations 2 and 3 had h' values of 0.51 and 0.52, respectively, classified as low diversity. The dominance index showed low dominance at station 1 (c = 0.36) and high dominance at stations 2 and 3 (c = 0.68 and c = 0.74). The evenness index indicated stable values at stations 1 and 2, but low values at station 3. Environmental factors such as temperature, pH, and DO were within the optimal range for gastropod life, while salinity showed extreme fluctuations that were likely to have influenced species distribution and diversity. These findings highlight the importance of managing pond environmental quality and using gastropods as biological indicators in evaluating aquatic ecosystem conditions. Keywords : gastropods, diversity, water quality, subsrate, Tarakan