Evaluation of bioaccumulation pattern of toxic heavy metals in commonly
consumed fishes from East Kolkata Wetlands, a designated Ramsar site of
India
Abstract
Waste water fed pisciculture is nowadays a feature that is common in
aquaculture belts across the globe. East Kolkata Wetlands (EKW) is a
nature’s wonder where waste water fed natural aquaculture belt is active
for more than 70 years now and is efficiently operating as a natural
waste management system.The peri urban wetland is also a site of
international importance and is listed in Ramsar. Field and lab-based
investigations were carried out with three commonly edible carp variety
of fishes such as Rohu (Labeorohita), Catla(Catlacatla) and Nile Tilapia
(Oreochromisniloticus) collected from ponds (bheries) of the wetland
located on the eastern fringes of Kolkata, India. The lab-based analysis
reveals the presence of many toxic heavy metals like Lead (Pb), Cadmium
(Cd), Chromium (Cr), and Mercury (Hg) in the samples with the seasonal
order of accumulation being monsoon >post-monsoon
>winter >pre-monsoon in the successive years
2016, 2017 and 2018. The order in which toxic metals are bio-accumulated
in fishes is Tilapia>Rohu>Catla.
Bioaccumulation of toxic heavy metals shows the trend
Pb>Cd>Cr>Hg across all the
seasons and years.The ambient media is also investigated to better
understand the bioaccumulation pattern at different trophic levels of
the ecosystem. Water and sediments were analyzed to evaluate the
contamination of toxic heavy metals from point as well as non-point
sources. In this study, the observed bioaccumulation pattern of the
toxic heavy metals in one of the fragile ecosystems raises questions of
environmental management. This study further raises considerable doubt
on environmental safety of daily consumed food items.