Diversity and Spatial Distribution of Macroalgae in Relation to Environmental Parameters in Teluk Tamiang Waters, Indonesia

This study analyzed macroalgae diversity, abundance, and spatial distribution in the waters of Teluk Tamiang, Pulau Laut, South Kalimantan, and their correlation with environmental parameters. Surveys were undertaken at three shallow sites utilizing 50-m belt transects with 1 × 1m quadrats. In situ data included temperature, salinity, pH, dissolved oxygen, current speed, depth, water clarity (Secchi depth), dissolved nutrients (nitrate, phosphate), and substrate type. Six species were identified: Caulerpa racemosa, Halimeda tuna, Padina australis, Sargassum oligocystum, Eucheuma cottonii, and Amphiroa fragilissima. Total density was ranked S3 > S2 > S1 (178, 122, and 61 individuals, respectively), with S2 having the highest species richness. Morisita's index identified three distinct dispersion patterns: uniform at S1, mixed (uniform-random-clumped) at S2, and clumped at S3. The principal component analysis (PCA) revealed that macroalgal density was positively connected with current speed, nitrate, and phosphate; S2 was correlated with pH and temperature; and S1 was negatively correlated with depth and water clarity, indicating light constraint. Nutrient contents (NO₃⁻ 1.1-2.1 mg L⁻¹; PO₄³⁻ 0.84-0.99 mg L⁻¹) were above guideline criteria, indicating enrichment. Currents (0.15-0.22 m s⁻¹) presumably improved water-mass exchange and reduced fine-sediment deposition on thalli. Overall, the combination of hydrodynamics, nutrients, and light, mediated by substrate heterogeneity, appears to shape local macroalgal composition and spatial patterns. Management should focus on nutrient load reduction, maintaining water clarity and circulation, and routinely monitoring key taxa as early indicators of coastal ecosystem change.