Heavy Metal Accumulation in Molluscs as Bioindicator of Contamination in Mangrove Sediments in Lake Uacon, Candelaria, Zambales

Date of Award


Document Type


Degree Name

Master of Science in Environmental Science


Environmental Science

First Advisor

Severino G. Salmo III, PhD; Neil H. Tan Gana, PhD


Heavy metals (HMs) are bioaccumulated in molluscs. These HMs are regulated by metallothionein (MT) in mollusc tissues. However, the MT contents may vary with HM, mollusc species and assemblage. In this study, the HM and MT contents were assessed in molluscs found in mangroves contaminated by mining effluents in Lake Uacon, Candelaria, Zambales. Molluscs were collected from arboreal and epifaunal assemblages with progressing distance from source of mining effluents. HMs (copper, chromium and nickel) were analyzed from mollusc tissues using Atomic Absorption Spectrophotometer (AAS) while MT concentrations were quantified using UV-Vis Spectrophotometer. Four species were analyzed from arboreal assemblage: Cassidula nucleus, Ellobium aurisjudae, Littorina scabra, and Neritina turrita. Only N. turrita was found in the epifaunal assemblage. Results indicate that HM concentrations varied with metal and with mollusc species. Ni was highest in E. aurisjudae (145.81 ± 127.33 ppm), Cu was highest in C. nucleus (205.66 ± 22.15 ppm) while Ni and Cr were highest in N. turrita. These concentrations exceeded the ecological thresholds by 182% in Ni, 685% in Cu and 234% in Cr. MT varied with species where E. aurisjudae, C. nucleus and N. turrita had 139.42 μg/g, 124.45 μg/g, 126.82 μg/g respectively. Among the molluscs, L. scabra had the lowest HM and MT concentrations. The high HM accumulation induced high MT concentration in mollusc tissues but varied with species. The results imply that the tolerance and adaptation of mollusc species from HM contamination can be regulated by MT. Such adaptation can be used as a bioindicator of HM contamination in mangroves.

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