Spatio-temporal dynamics of water quality variables of the southeastern Bay of Bengal, Bangladesh

The spatio-temporal dynamics of water quality variables play a critical role in evaluating the ecological health and environmental sustainability. This study investigates the spatio-temporal variability and pollution levels of water quality parameters along the southeastern Bay of Bengal (BoB) coast in Bangladesh. Sampling was conducted at nine ecologically critical sites in Cox’s Bazar over three dry-season months (December-February). Physicochemical parameters-including salinity, dissolved oxygen (DO), pH, conductivity, and nutrients-were measured using standardized methods. Statistical analyses, including one-way ANOVA, Principal Component Analysis (PCA), cluster analysis, and correlation matrices, revealed significant spatial heterogeneity and temporal trends. Notably, salinity and electrical conductivity exhibited wide spatial fluctuations (10.0-30.3 ‰ and 15.2-46.1 mS/cm, respectively), while DO, phosphate-phosphorus (PO₄-P), and nitrate-nitrogen (NO₃-N) showed significant temporal variation. Tukey’s post hoc test confirmed significant spatial differences in key water quality parameters among study sites, highlighting localized anthropogenic impacts on mudflat ecosystems. The correlation matrix highlighted strong positive associations (e.g., salinity with conductivity, r² = 1; NO₃-N with SiO₃, r² = 0.75) and negative interactions (e.g., DO with NO₃-N, r² = -0.85). PCA extracted five key components explaining 77.8% of the total variance, indicating strong influences from nutrient loading and anthropogenic pressures. The Water Pollution Index (WPI) ranged from 1.54 to 3.77, classifying most sites as moderately to heavily polluted, with Naf Jetty (WPI = 3.77) and Shaplapur (WPI = 3.58) identified as hotspots of contamination. These findings highlight the ecological stress faced by mudskipper habitats due to both natural hydro-climatic variations and increasing human activities. Policy recommendations include continuous site-specific water quality monitoring, stricter regulation of aquaculture and land-based runoff, and the implementation of conservation measures to protect mudflat ecosystems. The study provides vital baseline data for sustainable coastal management and underscores the use of mudskippers as effective bioindicators in tropical estuarine systems.