Trace metals concentration in water hyacinth implicates the saltwater barrage altered hydrography of Kochi backwaters, southwest Coast of India

This study in the Kochi backwaters (KBW) presents the distribution of 9 trace metals (Fe, Zn, Cu, Mn, Ni, Co, Cr, Cd, Pb) in different parts (root, stolon and leaf) of the common water hyacinth Eichhornia crassipes during three different seasons [Pre-Monsoon (PRM), Southwest Monsoon (SWM), and Northeast Monsoon (NEM)]. The hyacinth was collected from 4 sections upstream of the KBW where a saltwater barrage [Thannermukkom Barrage (TB)] prevents saltwater intrusion. Results showed that regardless of seasons, all the trace metals concentration in different parts of Eichhornia varied in the following order: roots > stolon > leaves. All the trace metals except Fe showed their highest concentration during the PRM when TB introduces stagnancy of the water upstream through flow restrictions. Instead, Fe was high during the SWM associated with increased river influx at that time. Overall results showed that the hydrographical alterations of TB upstream of KBW have clear imprints on the trace metals concentrated in the hyacinth Eichhornia crassipes.

Automated summary

The study in the Kochi backwaters found that the concentration of trace metals in different parts of the water hyacinth followed the order: roots > stolon > leaves across all seasons. The trace metals, except for Fe, showed highest concentration during the Pre-Monsoon season due to water stagnancy caused by flow restrictions, while Fe concentration was high during the Southwest Monsoon season with increased river influx. Overall, the results suggest that hydrographical alterations upstream have significant impacts on trace metal distribution in water hyacinths.