Background: Heavy metals are intrinsic, natural constituents of our environment and are
generally present in small amounts in natural aquatic environments. Humans may be contaminated by
organic and inorganic pollutants associated with aquatic systems by consumption of contaminated
aquatic foods from the environment. Relevant patents relating to heavy metal concentration in aquatic
molluscs were reviewed. Gastropods; a promising bio-indicator and bio-monitoring subject, abound in
brackish ecosystems in the Niger Delta, and are easily available for collection. Iko River Estuary, in Niger
Delta zone, is one of the popular coastal areas of Nigeria where massive oil exploitation, exploration,
production and refining processes take place.
Methods: The concentration of five heavy metals; Cadmium (Cd), Copper (Cu), Lead (Pb), Mercury
(Hg) and Zinc (Zn) in the tissues of periwinkle; Typanotonus fuscatus, a gastropod bought from fishers
fishing along the coast of Iko River Estuary was determined using UNICAM Solar Atomic Absorption
Spectrophotometer 969 model for five months.
Results: The results showed that Cd ranged from 68.83-130.5mg/kg with a mean value of
104.47±23.85mg/kg, Cu ranged from 34.9-73.62mg/kg with a mean value of 57.70±17.19mg/kg, Pb
ranged between 54.27-102.54mg/kg with a mean value of 85.03±18.52mg/kg, Mercury ranged from
0.01-1.84mg/kg with a mean value of 0.41±0.80mg/kg and Zn ranged from 270.2-508.16mg/kg with a
mean of 384.99±103.99mg/kg. The sequence of heavy metal concentration in the tissue of periwinkle
was; Zn ˃ Cd ˃ Pb ˃ Cu ˃ Hg while the sequence of non-essential metals was Cd ˃ Pb ˃ Hg.
Conclusion: Except for Mercury, the mean concentration of the metals was above the maximum permissible
limits recommended by relevant bodies and organizations. Hence, there is need for regular
monitoring of heavy metal concentrations in this water body and the aquatic organism inhabitants because
of the long term effects.