Study on the Phytoplankton Community Structure and their Environmental Drivers in a Brackish Coastal Lagoon Chilika Odisha

Abstract

Coastal ecosystems, one of the most productive ecosystems, are subjected to natural and newlineanthropogenic stresses. Environmental mechanisms and biotic associations that shape newlinephytoplankton communities remain poorly understood in tropical estuarine coastal lagoons. To newlineaddress this gap, the present study examined spatiotemporal patterns in phytoplankton newlinecommunities and environmental variables using a 5-year dataset (n = 780) collected from 13 newlinesampling stations in Chilika Lagoon, India. Generalized additive models were used to assess the newlinerelative contributions of seasonal, inter-annual, and sectoral components in explaining variation newlinein phytoplankton composition and their environmental drivers. Inter-annual Generalized additive newlinemodels (GAM) trends showed that salinity was lower during cyclone years (2013 and 2014). newlineGAM showed a declining trend in phytoplankton biomass, pH, and dissolved PO4 in the lagoon. newlineA total of 472 species of phytoplankton, mostly dominated by the Bacillariophyta (203 species), newlineChlorophyta (78 species), Euglenophyta (67 species), Dinophyta (66 species), Cyanophyta (52 newlinespecies), Chrysophyta (05 species), and Haptophyta (01 species) were recorded in this study. newlineHierarchical modeling of species communities revealed that in the lagoon ecosystem, salinity newline(44.48 ± 28.19%), water temperature (4.37 ± 5.65%), and season (4.27 ± 0.96%) accounted for newlinemaximum variation in the phytoplankton composition. Bacillariophyta (0.739) and Dinophyta newline(IV: 0.719) were positively correlated with salinity and emerged as top indicators for polyhaline. newlineIn contrast, Cyanophyta (IV: 0.806), Euglenophyta (IV: 0.790), and Chlorophyta (IV: 0.749) newlinewere negatively correlated with salinity and emerged as strong indicators for oligohaline regime. newlineThe responses of Dinophyta and Chrysophyta to environmental drivers were much more newlinecomplex, with random effects accounting for approximately 70 75% of the variation in their newlineabundances. Dinophyta (IV: 0.760), Cyanophyta (IV: 0.637), and Euglenophyta (IV: 0.517) were newlinepotential indicators of