Concentration factor of metals in zooplankton and their seasonality in Kalpakkam coast, southwest Bay of Bengal

Abstract

Concentrations of 12 different trace elements (Cd, Ce, Co, Cr, Cu, Fe, La, Mn, Ni, Pb, U and Zn) in dissolved form and in tissue of mesozooplankton isolated from Klapakkam coast were analyzed, to understand their bioaccumulation potential. Dissolved metal concentrations in water was found to be in the order Fe > Zn > Cu > Pb > U > Cr > Mn > Ni > La > Cd > Ce > Co, whereas, concentration in mesozooplankton tissues followed the trend of Fe > Zn > Mn > Cr > Ni > Pb > Cu > Ce > La > Co > U > Cd. Summer season was found to have high metal concentrations in the water and zooplankton tissue than the southwest and north east monsoon seasons. The bioconcentration factor (BCF) always remained high (BCF ≥ 1) indicating active accumulation of metals by mesozooplankton. The sequential trend of BCF was Mn > Ce > Fe > Cr > Ni > Co > La > Cu > Pb > Zn > Cd > U. Concentrations of rare earth elements viz. Ce and La, were significantly high in the study area in the dissolved form (range (mean ± SD): Ce: 0.2–3.8 μg L−1 (0. 7 ± 0. 8); La: 0.3–6.7 μg L−1 (1.8 ± 2.0)) and zooplankton tissue (Ce: 5.1–44.2 μg g−1 (21.55 ± 10.96); La: 2.5–20.9 μg g−1 (10.1 ± 5.4)) as well. The zooplankton community was dominated by copepods and there emerged a strong positive correlation between the soluble and accumulated metals in mesozooplankton in case of Zn and Cr. This study has provided a novel insight into metal distribution in zooplankton often act as the major food for marine fishes, and play an important role in the transfer of toxic metals in the marine food chain.

Keywords

• Bay of Bengal
• Bioconcentration
• Trace metal
• Zooplankton