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

Abstract

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.

Impact of the size of commercial bivalves on bioaccumulation and depuration of heavy metals

“…But these trials needed long periods for depuration that ranged from 50 days to 6 months. Other studies under took depuration in different experimental conditions (EL-Shenawy, 2004;Saed et al, 2004;El-Gamal, 2011). They found that it needs 2-32 days for complete depuration.…”

Health Risk Assessment Due to Heavy Metals Exposure via Consumption of Bivalves Harvested from Marudu Bay, Malaysia

“…El-Gamal [67] noticed that Zn, Pb, Ni, Mn, Cu, Cr and Cd can be reduced by 44%, 23%, 25%, 17%, 61%, 41% and 75% in clam, Paphia undulata after immersion in clean artificial seawater for 24 hours, respectively. The same author also showed that depuration process reduced the presence of Vibrio sp.…”

Depuration Times of Donax trunculus and Tapes decussatus

“…Many authors have reported depuration times for E. coli in various bivalve species. El-Gamal (2011) stated that E. coli can be completely excreted by Paphia undulata after 72 h of depuration, even if the initial amount is above the threshold level of category B. Barile et al (2009) reported that Chamelea gallina , which was contaminated with 4.0 Log 10 cfu/g E. coli , can reach the marketable level after 48 h depuration.…”

“…In several studies it has been stated that a three day depuration process could be enough for excretion of Salmonella ( Barile et al , 2009 ; El-Gamal, 2011 ). El-Shenawy (2004) has reported that clams containing Salmonella in the limits of category B, can be depurated by 90% of initial loads after 4 days.…”

“…However, clams containing Salmonella in the limits of category C, reduce initial load less than 50% in the same depuration period. El-Gamal (2011) has noted that Paphia undulata can depurate 97% of 3.5 Log 10 cfu/g Salmonella after three days depuration process. In another study, the depuration times for C. gallina and M. galloprovincialis , which were contaminated with S. typhimurium at the level of 4.0 Log 10 CFU/g, were determined as 72 and 36 h respectively ( Barile et al , 2009 ).…”