Ecological reorganisation of a central Indian reservoir by invasive aquatic macrophytes, with a checklist of the aquatic flora of the Satpura Reservoir

Abstract

The Satpura Reservoir, a 1,012 ha impoundment on the Tawa River in central India, was surveyed monthly from April 2020 to March 2021 to provide the first comprehensive inventory of its aquatic macrophytes and to assess the extent of aquatic weed invasion. Twenty-four species (three classes, ten orders, twenty genera) were recorded across 21 sites in four hydrological zones (fluvial, transitional, lacustrine, spill), with emergent (41.7%) and submerged (20.8%) growth forms predominating and Hydrocharitaceae – the most species-rich family. Three exotic species — Salvinia molesta, Pontederia crassipes and Ipomoea carnea — dominated the flora, contributing the highest Importance Value Indices (43.31, 21.68 and 28.16, respectively) and 45.57% of among-zone community dissimilarity (SIMPER). Species richness did not differ significantly among zones, but Shannon diversity and Pielou’s evenness did, indicating that zonation acted by reorganising relative abundance rather than by excluding species; NMDS, PERMANOVA (R2 = 0.388, p = 0.001) and ANOSIM (R = 0.482, p = 0.001) confirmed significant compositional differentiation. Invasive taxa exceeded half of total macrophyte abundance in every zone, peaking proportionally in the transitional zone (83.9%) but reaching the highest area-standardised pressure in the spill zone. These infestations impair fishing, navigation and thermal-power plant operations and threaten reservoir biodiversity. The results establish a baseline for monitoring and argue for a zone-prioritised, multi-method invasive-species management plan.