Fish parasites as bioindicators of the aquatic environmental quality of river saraswati west bengal

Abstract

Aquatic habitats become polluted by diverse industrial and domestic anthropogenic activities and natural surface run-offs etc. The nature and intensity of water pollution determine the effects on aquatic biota and the overall aquatic ecosystem health. The present study aimed at assessing the impact of the degraded physicochemical regime of river Saraswati, a polluted river having a historical legacy, on the parasitic infection and fish health, looking through the lens of haematological, histopathological and serum biochemical profile as well as to evaluate the role of fish parasite as bioindicators for aquatic environment quality. Two Water Quality Index (WQIs) were adopted as useful tools for assessing the overall riverine water quality status based on 10 physicochemical parameters of water samples from two strategic sites [(spot 1 (PR-1) and spot 2 (PR-2)] of the polluted river and the reference pond (RP), monitored once a month from March 2017 to February 2020. Low concentrations of dissolved oxygen (DO) and high concentrations of free carbon dioxide (CO2), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) indicate that the water quality of the river Saraswati is deteriorating due to organic loading. The index values derived from the WQIs indicated that the organic load was lower at PR-1 compared to PR-2. Water quality of PR-2 showed distinct seasonal variations. Due to the natural dilution effect, water quality became relatively better as reflected by the WQI score during monsoon and post-monsoon, when the water quality score was predominantly determined by turbidity. Water quality was very poor during both summer and winter, owing primarily to a precipitously lowered DO but elevated free CO2 and EC regime. Total 394 fish (Channa punctatus) grouped into control (CONT), controlled infected (CI), polluted river noninfected (PRNI), and polluted river infected (PRI) were examined for parasitic, haematological, histopathological and serum biochemical analyses. newline