SEASONAL VARIATION OF HEAVY METAL BIOACCUMULATION IN ZOOPLANKTON AND FISH LIVER IN THE GIRI RIVERINE ECOSYSTEM

Abstract

Water is the fundamental basis of the life support system, yet anthropogenic activities have significantly degraded water quality, adversely affecting aquatic life and depleting certain zooplankton and fish species. This research analyzed seasonal variations in heavy metal concentrations [chromium (Cr), nickel (Ni), arsenic (As), cadmium (Cd), and lead (Pb)] and their bioaccumulation in zooplankton and the liver of Tor putitora fish across different sites in the Giri River ecosystem in Himachal Pradesh, India, using an Inductively Coupled Plasma Emission Spectrometer (ICAP-6000 Series). The selected sites, characterized by distinct topographical features, pollution sources, and exposure to anthropogenic activities, were sampled during both the pre-monsoon and post-monsoon seasons to assess seasonal fluctuations in heavy metal concentrations and their bioaccumulation in aquatic organisms. The findings revealed significant site-specific and seasonal variations in metal concentrations, with downstream sites such as Bangran Giri Bridge generally showing higher pollutant levels compared to upstream locations like Giripul Bridge. These differences are attributed to anthropogenic factors such as wastewater discharge, vehicular emissions, mining activities, agricultural runoff, and urban pollution, which increase metal bioavailability in the river system. Seasonal trends indicated elevated metal concentrations during the pre-monsoon season, likely due to lower water flow, increased evaporation, sediment resuspension, and limited rainfall, leading to greater bioaccumulation. Post-monsoon concentrations were reduced, likely due to rainfall-induced dilution, pollutant removal, and sedimentation. Although concentrations remained within FAO’s permissible limits, indicating minimal immediate toxicological risk, the findings emphasize the need for continuous monitoring to track long-term trends and mitigate potential ecological impacts. This study underscores the influence of human activities and natural cycles on heavy metal bioaccumulation, highlighting the importance of targeted strategies to manage contamination and protect the Giri River ecosystem.