Response of Phytoplankton Community Structure to Light Availability, pH, DO, and Other Physicochemical Drivers in Kuala Gigieng Coastal Water

Abstract

Physicochemical gradients particularly light availability, pH, dissolved oxygen (DO), temperature, and salinity are known to structure phytoplankton communities in coastal ecosystems, but the degree to which each driver affects diversity and abundance varies among systems. This study examined the relationships between environmental drivers and phytoplankton community structure at three stations in Kuala Gigieng coastal system. Environmental variables were measured on four temporal occasions per station (salinity, temperature, turbidity, Secchi‑derived underwater light intensity, pH, DO). Pearson correlations between station‑averaged environmental variables and phytoplankton metrics were examined (n = 3). Turbidity was strongly positively correlated with phytoplankton abundance (r = 0.97), while light intensity showed a strong negative correlation with abundance (r = –0.99). Dissolved oxygen was negatively correlated with abundance (r = –0.76) but positively with H′ (r = 0.41). Salinity exhibited nearly perfect positive correlations with diversity and evenness and a negative correlation with dominance. pH displayed negative correlations with richness, abundance, and diversity. Temperature was moderately positively correlated with abundance (r = 0.78). In this system, turbidity and light emerge as dominant correlates of phytoplankton standing stock, while DO and salinity appear more closely linked to diversity patterns. These exploratory results provide a framework for understanding how physicochemical drivers influence phytoplankton community structure in tropical coastal waters.