The discharge of untreated sewage and effluents containing heavy metals from the shore based industries are known to accumulate in fishes of commercial importance. Heavy metals below certain concentrations do not affect the fauna and flora diversity of the marine environment. However, above this limit they tend to become toxic to the organisms, leading to deleterious effect on the overall productivity of the aquatic ecosystem. Thus, monitoring of these toxic heavy metals in the marine environment become indispensable so as to protect the coastal environment as well as the human beings. The present investigation was conducted to assess the heavy metal concentration and distribution in three locations of Thoothukudi coastal waters.
Monthly sampling of fish was taken from 3 stations including unpolluted station during period from October 2017 to May 2018. The fresh fish samples (Sardinella albella and Amblygaster sirm) were collected from landing centres of selected sites and kept in ice box brought it to the laboratory and the muscle tissue separated using sterile forceps and knives. The heavy metals were detected using Atomic Absorption Spectrophotometer (AAS).
The heavy metal values were also deducted in planktivorus fishes. The Fe values of Amblygaster sirm ranged from 0.029 µg/g (Station 3) to 8.443 µg/g (Station 1), Zn ranged from 0.058 µg/g (Station 3) to 1.096 µg/g (Station 2) Cu ranged from below the detectable range (Station 3) to 0.24 µg/g (Station 1, Cd ranged from below the detectable range (Station 3) to 0.06 µg/g (Station 2), Pb ranged from below the detectable range (Station 3) to 0.079 µg/g (Station 1), Ni ranged from below the detectable range (Station 3) to 0.276 µg/g (Station 1) and Cr ranged from 0.004 (Station 3) to 0.472 µg/g (Station 2).
The Fe values of Sardinella albella ranged from 0.25 (Station 2) to 6.36 µg/g (Station 1), Zn ranged from 0.087 (Station 3) to 3.97 µg/g (Station 2), Cu ranged from below the detectable range (Station 3) to 0.351 µg/g (Station1), Cd ranged from below the detectable range (Station 3) to 0.076 µg/g (Station 1), Pb ranged from below the detectable range (Station 3) to 0.124 µg/g (Station 2) , Ni ranged from below the detectable range (Station 3) to 0.338 µg/g (Station 1) and Cr ranged from below the detectable range (Station 3) to 0.352 µg/g (Station 2).
The present investigation indicated that most of the heavy metal concentrations found in the muscles of the two fish species were below the prescribed limit values (Cd and Pb < 0.3 ppm) for human consumption as recommended by INDIA FSSR (2011) and EU.