Species diversity of Oscillatoria in the Pokkali paddy fields of Chandiroor, Alappuzha District, Kerala, India

The Pokkali paddy fields of Alappuzha District represent a highly productive ecosystem characterized by rich algal biodiversity. The distribution of algal communities in this region is significantly influenced by climatic variations, biological interactions, physicochemical parameters, and cropping patterns. In the present study, the algal population in the Pokkali paddy fields of Chandiroor, Alappuzha was monitored across post-monsoon, pre-monsoon, and monsoon seasons from February 2023 to January 2024. The physicochemical parameters analyzed include temperature, pH, alkalinity, salinity, dissolved oxygen, and nutrient analysis such as nitrate, phosphate, and silicate. Water temperature reached its minimum during the monsoon season and was highest in the period preceding the rains. During the post-monsoon season, both pH and salinity levels showed an increase relative to the other seasonal periods. Alkalinity also showed an increase in the post-monsoon period. The concentration of dissolved oxygen increased during the monsoon period compared to the other seasons. Nitrate concentrations peaked during the monsoon, while phosphate content was highest in the pre-monsoon season. Silicate levels were lowest during the monsoon. Cyanophycean members were dominant in the study area, contributing significantly to the nitrogen-fixing biomass in the paddy fields. Among them, species of Oscillatoria were observed to be the most frequent and abundant throughout the study period. A total of fifteen Oscillatoria species were collected and identified using standard taxonomic references.