Assessing spatio-temporal dynamics of phytoplankton assemblage and ecohydrological interaction in a community managed reservoir using GIS for sustainable fisheries management

Abstract

The present study assessed the spatio-temporal dynamics of phytoplankton community structure and diversity using GIS platform, and their ecohydrological interactionsof a tropical reservoir located in Eastern India. Altogether, 74 species of phytoplankton belonging to 54 genera under seven taxonomic algal groups were recorded whose average annual abundance was 74.11 × 104 ± 17.73 × 104 cells l−1. Among seven algal groups, Chlorophyta, Cyanophyta, Bacillariophyta and Euglenophyta were remarkably influencing the total phytoplankton population contributing 97% of the total phytoplankton population in the reservoir. Cyanophyta absolutely dominated in the total phytoplankton compositions, and contributed a major share of 54% at the annual average level, however the species richness was maximum under the group Chlorophyta (35 genera). In total, thirteen phytoplankton taxa emerged as dominant (γ = < 0.02) across seasons. Among them, Phormidium sp. solely contributed (16.16%) to the total phytoplankton population, marked as dominant one in the reservoir. The diversity indices indicated the greater phytoplankton diversity in the lotic zone as compared to the transitional and lacustrine zone, showing significant variations (p<0.05) across seasons. PERMANOVA analysis exhibited a significant temporal variations of phytoplankton abundance (F=1.15, p=0.02) as well asenvironmental variables (F=1.82, p<0.05), but no significant spatial variations were recorded. The Principal Component analysis (PCA) revealed water temperature, transparency, total hardness, pH, specific conductivity, total alkalinity and nutrients parameters viz., phosphate, nitrate and silicate were the most important abiotic factors having the significant influence on the phytoplankton community compositions. Canonical Correspondence Analysis (CCA) depicted the environmental factors such as temperature, total alkalinity, total hardness, transparency, pH, and nutrients (NO3-N, PO4-P and SIO4-Si) were the determinants for the distribution of overall phytoplankton population especially the dominant phytoplankton species of the reservoir. The findings provide a better understanding of the influence of ecohydrology on phytoplankton community of a community managed reservoir and also discuss management and researchable issues considering the feeding guild of reservoir fishes and phytoplankton assemblage for ecosystem based conservation and management.