Journal of Global Ecology and Environment

Diatom communities play a pivotal role in regulating primary productivity in wetland and estuarine ecosystems, yet comparative assessments of their functional contribution across tropical Ramsar wetlands remain limited. The present study evaluates diatom-mediated productivity patterns in Ashtamudi Lake and Vembanad Lake, two ecologically significant wetlands along the southwest coast of India. Phytoplankton samples were collected during June–December 2023, and Bacillariophycean taxa were identified and quantified using standard microscopic techniques. Diatom abundance (Ind./L.) was used to estimate standing crop, and assemblages were analysed based on centric-pennate composition and functional group classification (planktonic, benthic, and epiphytic). Multivariate analyses, including similarity indices and NMDS ordination, were employed to interpret productivity gradients. Results revealed a higher total diatom standing crop in Ashtamudi Lake, with dominance of pennate (73.17%) and benthic diatoms (47.05%), indicating strong sediment-water column coupling and benthic-driven productivity. In contrast, Vembanad Lake showed a relatively higher contribution of centric (32.50%) and planktonic diatoms (46.12%), reflecting enhanced pelagic productivity. Integrated visualization using a radar plot effectively synthesized multiple productivity attributes and highlighted functional differentiation between the wetlands. The study demonstrates that diatom community structure provides a robust proxy for comparative productivity assessment and underscores the ecological significance of Bacillariophyceae in monitoring and management of tropical Ramsar wetlands under changing environmental conditions.