Spatio-temporal dynamics of phytoplankton diversity and community structure in relation to environmental variables in the Northwest Coasts of India

The primary objective of this study was to investigate the temporal and spatial variations in phytoplankton diversity, community composition, and associated environmental variables within Manori Creek, Northwest Coasts of India. Monthly surface water samples were systematically collected from January 2022 to February 2023 at three designated stations. The taxonomic analysis identified 114 phytoplankton species belonging to 67 genera, 53 families, and nine different classes, comprising Bacillariophyceae (29.8%), Mediophyceae (25.4%), Dinophyceae (19.3%), Coscinodiscophyceae (15.8%), Cyanophyceae (4.4%), Chlorophyceae (2.6%), Eustigmatophyceae (0.9%), Noctilucophyceae (0.9%), and Zygnematophyceae (0.9%). Cluster analysis and non-metric multidimensional scaling revealed three distinct clusters with unique spatial and temporal characteristics. The estuarine region at station 2 exhibited the highest species richness, while the riverine region at station 3 demonstrated the highest species diversity and dominance. The research outcomes revealed that phytoplankton diversity, richness, and evenness indices were highest during the monsoon and lowest during the pre-monsoon. Biota-environment stepwise analysis (BIO-ENV) results indicated that air temperature, salinity, pH, transparency, nitrite, total phosphorus, and silicate (Spearman coefficient “ ρ ” = 0.8327) are deterministic environmental variables that influence the distribution and community structure of phytoplankton. The canonical correspondence analysis further elucidated that the abundance of phytoplankton is primarily influenced by variables such as transparency, pH, total phosphate, nitrite, temperature, silicate, and chlorophyll-a concentration. The novelty of this research lies in its holistic approach to considering its unique environmental conditions incorporating a wide range of physical, chemical, and biological parameters that collectively influence phytoplankton dynamics.