Speciation of metals in sediments and their bioaccumulation by edible bivalves (Cassosstrea spp. and Polymesoda spp.) in the aquatic bodies of Goa, west coast of India

Abstract

Total metals and their speciation were investigated in sediments from lower Chapora Estuary, middle Zuari Estuary, and Moira River in Goa, India. The study aims to understand metal bioavailability in sediments and bioaccumulation in two edible bivalves (Cassosstrea spp. and Polymesoda spp.) in three water bodies of different lengths, catchment areas, hydrodynamics, and anthropogenic stress. Considerable differences in total metal level (Mn and/or Zn) from November to December were attributed to their additional input and variation in physicochemical processes. Contamination factor revealed moderate contamination by Zn at Chapora (November), while Zuari was moderately contaminated by Zn, Cu, and Co. The presence of metals in considerable or significant amounts in bioavailable fractions indicated their bioavailability. Variation in metal accumulation in gills, adductor muscle, and digestive gland at three stations and between months was the result of varying hydrodynamics, trophic levels, feeding habits, and enrichment gradients of metals. The abundance of metals in water, sediments, and bivalves when compared revealed variations in accumulation of metals. This might be attributed to the differential response of species to varying physical and biological factors at study sites. Bivalves showed a selective preference for Zn at three stations highlighting its importance in biological activities. Moreover, metals in bivalves at one or more stations exceeded the standard permissible limit and, thus, indicated their toxicity to bivalves.