THE RELATION BETWEEN THE PHYSICAL AND CHEMICAL CONDITIONS OF WATERS AND THE PRESENCE OF WHALE SHARKS (Rhincodon typus) IN THE BOTUBARANI TOURISM AREA, GORONTALO

Abstract

Whale sharks (Rhincodon typus) exhibit consistent seasonal aggregation in the Botubarani tourism area, Gorontalo, yet the local physicochemical mechanisms governing their occurrence remain poorly quantified. This study aimed to characterize water physicochemical conditions and identify the environmental parameters most strongly associated with whale shark presence at the coastal microhabitat scale. Data were collected across three stations at Botubarani Station III using a water quality meter, Secchi disk, and spectrophotometric nutrient analysis, then analyzed through Pearson correlation, Principal Component Analysis (PCA), and Redundancy Analysis (RDA). Correlation results revealed organized parameter interactions, with strong positive correlations for temperature–salinity (r = 0.78), nitrate–phosphate (r = 0.84), and water clarity–dissolved oxygen (r = 0.65). PCA resolved two dominant environmental gradients: a physical water-mass gradient (PC1, ~71.4%) and a nutrient gradient (PC2, ~28.6%). RDA cumulatively explained ~69.9% of whale shark distribution variance, identifying temperature, dissolved oxygen, and water clarity as primary positive determinants, while turbidity and nutrients exhibited negative associations. These findings support a bio-physical coupling framework, demonstrating that microscale physicochemical variability mediates trophic dynamics and habitat use by R. typus in semi-enclosed tropical coastal systems. Results provide a quantitative baseline for environment-based monitoring strategies in whale shark conservation management at Botubarani.