The effect of depuration on heavy metals, petroleum hydrocarbons, and microbial contamination levels in Paphia undulata (Bivalvia: Veneridae)

Abstract

The depuration of 8 heavy metals (Zn, Pb, Ni, Mn, Cu, Cr, Co and Cd), total petroleum hydrocarbons and pathogenic bacteria of Paphia undulata was tested and the survival of depurated clams was evaluated. Investigated samples were collected from Ismailia, Egypt. The initial metal concentrations were significantly higher in the whole soft tissues than in water and sediment except for Mn. After 24 h depuration, Zn, Pb, Ni, Mn, Cu, Cr and Cd were significantly reduced to 44, 23, 25, 17, 61, 41, and 75%, respectively. After three days of depuration the reduction was significant only for Cu, Cr, Co and Cd (27, 15, 23 and 52%, respectively). The total petroleum hydrocarbons were reduced significantly to 72% after three days of depuration, while after 24 h they were reduced to 90% compared to their initial concentrations. Four pathogenic bacteria were identified in the soft tissues of P. undulata (Vibrio sp., Shigella sp., Escherichia coli and Salmonella sp.). After one-day depuration the results evidenced the mean microbial reduction to 75, 31, 68, and 36%, respectively, compared to their initial counts. After three days of depuration the counts of Vibrio sp. and Salmonella sp. were reduced to 3% and 8%, respectively, while Escherichia coli was not detected on the third day. Shigella sp. was increased by 22% compared to the first day of depuration. The viability and mortality were not influenced by the depurative treatment.