Effect Of Depuration Research Articles

Modelling the dynamics of ambient dose rates induced by radiocaesium in the Fukushima terrestrial environment

Since the Fukushima accident, Japanese scientists have been intensively monitoring ambient radiations in the highly contaminated territories situated within 80 km of the nuclear site. The surveys that were conducted through mainly carborne, airborne and in situ gamma-ray measurement devices, enabled to efficiently characterize the spatial distribution and temporal evolution of air dose rates induced by Caesium-134 and Caesium-137 in the terrestrial systems. These measurements revealed that radiation levels decreased at rates greater than expected from physical decay in 2011-2012 (up to a factor of 2), and dependent on the type of environment (i.e. urban, agricultural or forest). Unlike carborne measurements that may have been strongly influenced by the depuration of road surfaces, no obvious reason can be invoked for airborne measurements, especially above forests that are known to efficiently retain and recycle radiocaesium.The purpose of our research project is to develop a comprehensive understanding of the data acquired by Japanese, and identify the environmental mechanisms or factors that may explain such decays. The methodology relies on the use of a process-based and spatially-distributed dynamic model that predicts radiocaesium transfer and associated air dose rates inside/above a terrestrial environment (e.g., forests, croplands, meadows, bare soils and urban areas).Despite the lack of site-specific data, our numerical study predicts decrease rates that are globally consistent with both aerial and in situ observations. The simulation at a flying altitude of 200 m indicated that ambient radiation levels decreased over the first 12 months by about 45% over dense urban areas, 15% above evergreen coniferous forests and between 2 and 12% above agricultural lands, owing to environmental processes that are identified and discussed. In particular, we demonstrate that the decrease over evergreen coniferous regions might be due the combined effects of canopy depuration (through biological and physical mechanisms) and the shielding of gamma rays emitted from the forest floor by vegetation. Our study finally suggests that airborne surveys might have not reflected dose rates at ground level in forest systems, which were predicted to slightly increase by 5 to 10% during the same period of time.

Mercury depuration effectiveness on green mussel (Perna viridis L.) and blood cockle (Anadara granosa L.) from Jakarta Bay using ozone, chitosan and hydrodynamic technique

Depuration has been used to eliminate microorganism and toxic chemical contaminants in bivalve. However, scientific research still needs to discover the effectiveness of depuration. This research aimed at assessing the best depuration effectiveness in decreasing mercury (Hg) concentration level in two species of bivalves, green mussel (Perna viridis L.) and blood cockle (Anadara granosa L.). The depuration treatments applied 1.5 ppm ozon, 0.5 ppm chitosan, hydrodynamic technique (1.3 m/s), combination between hydrodynamic-ozon, hydrodynamic-chitosan and ozon-chitosan. The experiment were conducted in mini aquaria for 60 minutes. Mercury concentration was measured in 10 g dry weight of green mussel (4.05±0.020 ppm) and blood cockle (3.27 ± 0.666 ppm). The result showed that mercury depuration were highly effective by combination of ozone-chitosan in green mussel (96.51%) and 1.5 ppm ozone in blood cockle (87.06%).

Modelling the dynamics of ambient dose rates induced by radiocaesium in the Fukushima terrestrial environment

Since the Fukushima accident, Japanese scientists have been intensively monitoring ambient radiations in the highly contaminated territories situated within 80 km of the nuclear site. The surveys that were conducted through mainly carborne, airborne and in situ gamma-ray measurement devices, enabled to efficiently characterize the spatial distribution and temporal evolution of air dose rates induced by Caesium-134 and Caesium-137 in the terrestrial systems. These measurements revealed that radiation levels decreased at rates greater than expected from physical decay in 2011–2012 (up to a factor of 2), and dependent on the type of environment (i.e. urban, agricultural or forest). Unlike carborne measurements that may have been strongly influenced by the depuration of road surfaces, no obvious reason can be invoked for airborne measurements, especially above forests that are known to efficiently retain and recycle radiocaesium. The purpose of our research project is to develop a comprehensive understanding of the data acquired by Japanese, and identify the environmental mechanisms or factors that may explain such decays. The methodology relies on the use of a process-based and spatially-distributed dynamic model that predicts radiocaesium transfer and associated air dose rates inside/above a terrestrial environment (e.g., forests, croplands, meadows, bare soils and urban areas). Despite the lack of site-specific data, our numerical study predicts decrease rates that are globally consistent with both aerial and in situ observations. The simulation at a flying altitude of 200 m indicated that ambient radiation levels decreased over the first 12 months by about 45% over dense urban areas, 15% above evergreen coniferous forests and between 2 and 12% above agricultural lands, owing to environmental processes that are identified and discussed. In particular, we demonstrate that the decrease over evergreen coniferous regions might be due the combined effects of canopy depuration (through biological and physical mechanisms) and the shielding of gamma rays emitted from the forest floor by vegetation. Our study finally suggests that airborne surveys might have not reflected dose rates at ground level in forest systems, which were predicted to slightly increase by 5–10% during the same period of time.

Analysis of Vibrio vulnificus Infection Risk When Consuming Depurated Raw Oysters

A beta Poisson dose-response model for Vibrio vulnificus food poisoning cases leading to septicemia was used to evaluate the effect of depuration at 15°C on the estimated health risk associated with raw oyster consumption. Statistical variability sources included V. vulnificus level at harvest, time and temperature during harvest and transportation to processing plants, decimal reductions (SV) observed during experimental circulation depuration treatments, refrigerated storage time before consumption, oyster size, and number of oysters per consumption event. Although reaching nondetectable V. vulnificus levels (<30 most probable number per gram) throughout the year and a 3.52 SV were estimated not possible at the 95% confidence level, depuration for 1, 2, 3, and 4 days would reduce the warm season (June through September) risk from 2,669 cases to 558, 93, 38, and 47 cases per 100 million consumption events, respectively. At the 95% confidence level, 47 and 16 h of depuration would reduce the warm and transition season (April through May and October through November) risk, respectively, to 100 cases per 100 million consumption events, which is assumed to be an acceptable risk; 1 case per 100 million events would be the risk when consuming untreated raw oysters in the cold season (December through March).

Effects of depuration on metal levels and health status of bivalve molluscs

Depuration has been mandatory to eliminate microorganisms in bivalve molluscs, but not to eliminate toxic chemicals, since there is still shortage of scientific evidence about the efficacy of depuration to decrease the levels of toxic chemicals in bivalves. This study aims to assess the effects of depuration on the levels of toxic, macro and trace elements in three bivalve species (Ruditapes philippinarum-RP, Mytilus galloprovincialis-MG and Scrobicularia plana-SP), taking into account their condition. During depuration, a significant reduction of elements occurred in RP (Fe, Pb, Cu, Rb, Br, Hg, Cd and As), MG (Cl, Sr, Fe, Pb and Br) and SP (Fe, Pb, Cu and Rb), while an increase was registered for other elements in RP (Cl and Sr), MG (S and Zn) and SP (Cl, Zn, Br and Sr). After two days of depuration, Pb in SP had decreased to levels below the permissible limits, thus allowing this species to be acceptable for human consumption as far as toxic elements are concerned. SP revealed the highest glycogen levels compared to the other species indicating different physiological requirements. However, in this species glycogen levels significantly decreased after two days of depuration and mortality increased. In contrast, in MG and RP glycogen and mortality did not vary significantly during depuration. Therefore, SP should be only depurated for a maximum period of two days. Overall, the results of this study are particularly useful to retailers to ensure high quality bivalve products for consumers. Additionally, glycogen can be used as a suitable biomarker of healthy status of bivalve species during depuration.

Geosmin off-flavour in pond-raised fish in southern Bangladesh and occurrence of potential off-flavour producing organisms

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 5:107-116 (2014) - DOI: https://doi.org/10.3354/aei00100 Geosmin off-flavour in pond-raised fish in southern Bangladesh and occurrence of potential off-flavour producing organisms Mikael A. Petersen1, Md. Ariful Alam2, Md. Mizanur Rahman2, Md. Lokman Ali2, Sultan Mahmud2, Louise Schlüter3, Niels O. G. Jørgensen4,* 1Department of Food Science, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg, Denmark 2Faculty of Fisheries, Patuakhali Science and Technology University, Dumki, Patuakhali 8602, Bangladesh 3Environment and Toxicology, DHI Group, Agern Allé 5, 2970 Hørsholm, Denmark 4Genetics and Microbiology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg, Denmark *Corresponding author: nogj@plen.ku.dk ABSTRACT: Pangas Pangasianodon hypophthalmus and tilapia Oreochromis niloticus were cultivated for 6 mo in earthen ponds in Bangladesh to examine occurrence of the off-flavour geosmin in water and fish and to test procedures for reduction of off-flavour. In the ponds (~1 m depth and area of 400 m2), the average geosmin concentration was 3.9 ng l-1 (range 0.2 to 20 ng l-1). No effects of season or water treatment (sand filtration or probiotic microbes) were found. The content of geosmin in the fish was 21 ng kg-1 (range: 0.0 to 91 ng kg-1) for pangas and 17 ng kg-1 (range: 0.0 to 68 ng kg-1) for tilapia. Water treatment reduced the geosmin content by 56 to 74% in pangas, but no effect was found in tilapia. Likewise, depuration for ≥12 h in groundwater lowered the geosmin content in pangas (by 65 to 90%) but not in tilapia. Sensory analysis indicated a positive effect of both water treatment and depuration, and the fish were graded ‘no or mild flavour’ after such treatment, compared to ‘strong off-flavour’ in controls. Abundance analyses of known off-flavour producing microorganisms (streptomycete bacteria and cyanobacteria) showed a high density of streptomycetes (0.5 to 13% of the bacterial population), while cyanobacteria made up a maximum of 9.3% of the phytoplankton biomass or were absent. This first study on off-flavours in pangas and tilapia in Bangladeshi ponds indicates that geosmin was not a major off-flavour in the fish, but improvement of sensory quality by water treatment and depuration suggests that other, unidentified off-flavours were present in the fish. KEY WORDS: Off-flavour · Aquaculture · Pangasianodon hypophthalmus · Oreochromis niloticus · Streptomycetes · Cyanobacteria · Geosmin · GC-MS · Sensory analysis Full text in pdf format PreviousNextCite this article as: Petersen MA, Alam MA, Rahman MM, Ali ML, Mahmud S, Schlüter L, Jørgensen NOG (2014) Geosmin off-flavour in pond-raised fish in southern Bangladesh and occurrence of potential off-flavour producing organisms. Aquacult Environ Interact 5:107-116. https://doi.org/10.3354/aei00100 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 5, No. 2. Online publication date: May 08, 2014 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2014 Inter-Research.

Effectiveness of depuration for hepatitis A virus removal from mussels (Mytilus galloprovincialis)

The efficacy and kinetic of depuration of hepatitis A virus (HAV) were evaluated under experimental conditions with Mediterranean mussels (Mytilus galloprovincialis) subjected previously to bioaccumulation processes. Seven independent trials (70kg of mussels each) were performed in a closed experimental system using two different water temperatures (13 and 17°C) during 7days. The real time RT-PCR technique with TaqMan probes was used for viral quantification. Qualitative infectivity assays were conducted to test the presence of infectious viral particles at the end of the depuration period. The depuration trials showed an average reduction of HAV levels of aproximately 1.1 Log units (>90%). However, the average final viral loads in shellfish samples remain at relatively high levels (6.5×103 RNA copies/g digestive tissue) and still infectious. A positive correlation between the initial and the final numbers of the viral RNA copies was observed. The reduction of HAV showed a two-phase removal kinetic, an initial logarithmic trendline, with a rapid reduction of viruses during the first 24–48h of depuration, and a subsequent stabilization with a slower depuration rate until the end of the process.

Viral elimination during commercial depuration of shellfish

The effectiveness of depuration for the removal of hepatitis A virus (HAV), norovirus (NoV) genogroups I (GI) and II (GII), and F+RNA bacteriophage (F+RNA) was evaluated for pullet carpet shell clams (Venerupis pullastra) and Mediterranean mussels (Mytilus galloprovincialis). The objective was to compare the behaviour of the different pathogens under commercial depuration conditions during 7 days in an authorized plant. Standard double agar overlay method (ISO 10705-1) was employed for F+RNA quantification. Recently developed ISO/TS 15216:2013 standard method, based on RT-real time PCR, were employed for the quantification of HAV and NoV. The reduction of F+RNA showed a two-phase depuration kinetic. The average reduction rates were 1-log units for clams and 2-log units for mussels, with residual levels after the process of 6.3 × 103 and 8.3 × 101 F+RNA/100 g, respectively. HAV, NoV GI and GII were detected intermittently throughout the entire process, ranging mostly from 103 to 105 RNA copies/g digestive tissue (DT). NoV GI showed the higher viral levels followed by NoV GII and HAV. All of them were detected in clams after seven days of depuration, however, in mussels only NoV GI was detected after the process. Generally, clams showed slower depuration rates and higher contamination levels for all viruses analysed.

Bioaccumulation—Depuration kinetics and effects of phenanthrene on Mediterranean mussel (Mytilus galloprovincialis)

In this study, Mediterranean mussel species, Mytilus galloprovincialis, were exposed to phenanthrene (PHE) due to its ubiquitousness and bioavailability in the aquatic environment. Kinetic parameters of the PHE bioaccumulation and depuration were calculated for an 11-day uptake and subsequent 11-day depuration periods. Those values of kinetic rate constants for uptake and depuration of PHE were calculated as varying between 93–177 and 0.18–0.25, respectively. Negative correlation was observed between the PHE concentrations and kinetic rate constants. Bioaccumulation Factors (BAFs) for the mussels exposed to different PHE concentrations were calculated from both kinetic rate constants and from the experimental data and found between 509–701 and 441–658, respectively. Experimental quantitative structure activity relationship (QSAR) values for PHE were found comparable to the calculated QSARs reported in literature. Two sub-lethal biomarker methods (filtration rate and lysosomal stability) were applied to observe the responses of the mussels throughout the experimental period. Results of both biomarkers show that PHE negatively affects mussels during the uptake of PHE, and mussels were able to recover physiologically at the end of depuration period according to the filtration rate results.

Effects of depuration on the element concentration in bivalves: Comparison between sympatric Ruditapes decussatus and Ruditapes philippinarum

Organisms living in coastal ecosystems are frequently subjected to anthropogenic pressures such as metals. Metals, especially those not required for metabolic activity (e.g. mercury, lead and cadmium) can be toxic even at quite low concentrations not only to organisms that accumulate them, but also to their consumers. Throughout the world, Ruditapes decussatus and Ruditapes philippinarum have been successfully commercialised for human consumption and for monitoring environmental conditions such as contamination. These two clam species share similar habitats and requirements, successfully competing both in the natural environment and in aquaculture farms. Because differences in metal accumulation may exist between R. decussatus and R. philippinarum, different risks to public health may overcome as well as distinct ecological implications. The effect of depuration on the metal burden and biochemical status of both clams species may also diverge and since the information available is subjective and scarce, the aims of the present study were to: 1) assess the total metal accumulation and intracellular partitioning, at natural conditions, in the two clam species collected at the same site; 2) evaluate the effect of depuration as a mean of reducing the levels of distinct elements, assessing also the effect of depuration time (2 and 7 days); 3) investigate the efficiency of depuration by biochemical status of the two bivalve species, evaluating changes in lipid peroxidation and activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and of glutathione S-transferase (GST). Metal chelation by metallothioneins (MTs) was also determined. The results obtained showed that concentration of elements in clams was low, presenting very similar concentration levels for all elements. The present work further demonstrated that the total element concentration decreased in the shorter depuration period (2 days) and that R. decussatus and R. philippinarum partitioned elements preferentially in the insoluble fraction. The percentage of elements in the soluble fraction was lower in the longer depuration period, reducing the dietary bioavailability of elements and thus the health risk to consumers of depurated bivalves. In general, LPO, CAT, SOD and GSTs showed a decreased from environmental to depuration conditions, revealing that depuration reduces the oxidative stress that organisms were subjected in the environment. The lower MTs production observed in the longer depuration period, although no significantly different from the remaining periods, may be explained by the distinct metal allocation between both soluble and insoluble fractions.

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

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.

Sand elimination by Donax scortum (Dance, 1982) (Bivalvia: Donacidae)

Donax scortum (Dance, 1982) is an Indo-Pacific infaunal filter-feeding bivalve common on sandy beaches in Thailand. Like many burrowing bivalves, it tends to accumulate sand in its body. Depuration reduces the gut contents and eliminates sand from different body fractions, providing cleaning, and ensuring safety for human consumption. In our laboratory investigation, the effect of depuration on the rate of sand elimination in D. scortum was studied using a 3 x 2 factorial design, with treatment at three salinity levels (25, 30 and 35 ppt) and under two light conditions (dark and light). The total sand content (TSC) in guts did not differ significantly among the treatments over the depuration periods (p 0.05). The rate of sand elimination (RSE) by D. scortum also did not differ significantly among salinity/light treatments after acclimation for 12 and 48 h (p 0.05). How-ever, mean RSE was significantly different among treatments for 24 h (p&lt;0.05), with the highest RSE observed at a salinity 30 ppt in the dark. The cumulative amount of sand removed increased from 36.4 to 70.3% after 12 h acclimation, to 98.1 to 98.9% after 48 h acclimation. The condition index of D. scortum did not differ significantly among treatments after 48 h acclimation (p 0.05).

Reproductive failure of the red shiner (Cyprinella lutrensis) after exposure to an exogenous estrogen

Endocrine disrupting chemicals (EDCs) have been detected in surface waters worldwide and can lead to developmental and reproductive disruption in exposed fishes. In the US Great Plains, EDCs are impacting streams and rivers and may be causing adverse reproductive effects. To examine how estrogenic EDCs might affect reproductive success of plains fishes, we experimentally exposed male red shiners ( Cyprinella lutrensis ) to exogenous 17β-estradiol. We characterized the effects of estradiol on male gonadal histology and secondary sexual characteristics, determined whether exposure reduced reproductive success, and examined the effects of depuration. Adults were exposed to a mean concentration of 70 ng·L−1 estradiol, a solvent control, or a water control for at least 83 days. Male exposure to estradiol resulted in elevated plasma vitellogenin concentrations, changes in spermatogenesis, reduced mating coloration and tubercles, altered mating behaviors, and reduced reproductive success with no viable progeny produced. Reproductive endpoints improved upon depuration (28 days). Exposure to estradiol had significant adverse effects on red shiners, indicating that wild populations may face developmental and reproductive difficulties if they are chronically exposed to estradiol.

Enrichment of the African catfish Clarias gariepinus (Burchell) with functional selenium originating from garlic: effect of enrichment period and depuration on total selenium level and sensory properties

We wanted to optimize the procedure for the selenium enrichment of farmed African catfish, using garlic as dietary selenium source. In the first experiment we established the relation between the length of the selenium enrichment period and the resulting total selenium level in the fillet of the fish. It was found that at a dietary level of 11.7 mg kg−1 Se, a total selenium level in the fillet of 0.7 mg kg−1 was reached in a relatively short enrichment period of 10 days before harvest. In the second experiment we studied the effect of depuration on the selenium level in the fillet and the sensory properties of selenium-enriched African catfish. It was found that total selenium levels in the fillet were not affected during a 7-day depuration period, while garlic odours and flavours in the raw and cooked fillets were significantly reduced after 2 days of depuration. We concluded that selenium enrichment of farmed African catfish can be obtained by selenium-enriched finishing diets, while garlic odours and flavours resulting from dietary garlic can be effectively reduced in the fillet during a short depuration period without negatively affecting fillet levels of total selenium.

Foodborne and indicator bacteria in farmed molluscan shellfish before and after depuration.

Galicia's coast (northwestern Spain) is a major producer of bivalve molluscs. Over an 18-month period, the presence of Salmonella, Aeromonas, Plesiomonas shigelloides, Vibrio parahaemolyticus, and Clostridium botulinum was determined by PCR methods in mussels (22 batches) and infaunal bivalves (31 batches of clams and cockles) before and after depuration. All batches were harvested from Galician class B harvesting areas where bivalve molluscs must not exceed 4,600 Escherichia coli per 100 g of flesh and liquor in 90% of the samples. Virulence-associated genes of Salmonella (invA), Aeromonas (aerA, hlyA, alt, ast, and laf), P. shigelloides (hugA), V. parahaemolyticus (tdh and trh), and C. botulinum (BoNT) were not detected. The pR72H chromosomal DNA fragment, which is conservative in V. parahaemolyticus strains, was detected in five (4.7%) samples. A number of 192 suspect isolates did not fit the description of clinical Aeromonas phenospecies, pathogenic Vibrio spp., or P. shigelloides. The effectiveness of commercial depuration in reducing bacterial indicators was also examined. E. coli was reduced to < or = 230/100 g of flesh and liquor in 90.9% of mussel lots but in only 70.9% of infaunal bivalve lots. For total coliform elimination, mussels were also more effective. Total counts significantly (P < 0.005) correlated with numbers of Pseudomonas, Aeromonas, and Vibrio. Our data indicate that Salmonella and pathogenic bacteria indigenous to estuarine environments do not appear to be significant hazards in Galician molluscan shellfish. A reason for concern, however, is that clearance of E. coli to acceptable levels was not always achieved especially in infaunal bivalves.

EFFICACY OF DEPURATION ON SAFETY OF MEDITERRANEAN MUSSELS (Mytilus galloprovincialis) REARED IN THE OLBIA GULF

The aim of the present study was to investigate the effect of depuration on the safety of Mediterranean mussels harvested in the Olbia gulf and to evaluate the efficacy of E.coli and Salmonella spp. as indicators of the presence of naturally occurring Vibrios and other pathogens (viruses causing hepatitis, L.monocytogenes and S.aureus). Samples of mussels belonging to 5 batches of products, from 2 Depuration Centers, were collected before depuration (T0), after 4h (T4) and at the end of depuration (T8). Results showed an overall efficacy of the depuration in respect to E.coli moderate counts. A depuration for ~8 hours led to a rapid decline in the concentration, complying to the Food Safety Criteria of the Reg. (EC) 2073/2005. The decline in numbers of E.coli, does not correlate with the presence of naturally occurring Vibrios, which decline at an even slower rate. The adoption of shorter treatments times for mussels with high initial counts of Vibrios could lead to a reduction unfitted to guarantee the safety of consumers.

The effect of long-term depuration on levels of oxidative stress biomarkers in mullets (Mugil cephalus) chronically exposed to contaminants

The present study aimed to obtain additional data on the effect of long-term depuration on the levels of oxidative stress biomarkers, and to clarify the role of mullets for monitoring pollution in River Douro estuary. Mullets chronically exposed to a mixture of contaminants in Douro estuary were captured in Spring of 2001, 2002 and 2003. The activities of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX); and oxidative damages in lipids (lipid peroxidation) and in proteins (protein carbonyl content) were assessed at capture day and after transfer to unpolluted seawater for 1, 4 and 8 months. An overall decrease in the activities of the antioxidant enzymes was detected, except for the GPX after 4 months depuration. CAT activity exhibited the more significant decrease at the end of the long-term depuration. The decrease in SOD activity after 1 month of depuration was then maintained during the remaining depuration period. Regarding oxidative damages, a decrease in lipid peroxidation as well as the content of oxidised proteins was observed during depuration. Indeed, at capture the activities of antioxidant defences were higher as a result of the formation of reactive oxygen species (ROS) from the metabolism of pollutants. The oxidative damaged molecules were repaired or degraded during the depuration period, supporting the use of such damages as indicators of exposure to pro-oxidant pollutants.

The effect of long-term depuration on phase I and phase II biotransformation in mullets (Mugil cephalus) chronically exposed to pollutants in River Douro Estuary, Portugal

Pollutants such polycyclic aromatic hydrocarbons (PAHs) are released into the environment by urban communities and industries and the enzymes that catalyse the biotransformation of pollutants play a key role regarding the accumulation of these compounds in fish species inhabiting these areas. In this study the relationship between phase I (EROD activity) and phase II (GST activity) and PAH metabolites was measured in grey mullet (Mugil cephalus) after capture in the Douro estuary, and after long-term depuration in an unpolluted laboratory environment. The results showed a significant decrease in EROD activity after 1 month and in bile metabolites after 4 months in captivity, with both maintaining reduced levels at 4 and 8 months depuration. Liver GST activity did not showed significant changes. This study provides evidence that Douro estuary waters contain bioavailable PAHs that can be associated with the induction of cytochrome P450, and that mullets have the ability to metabolise and eliminate PAHs.

Heavy‐metal and microbial depuration of the clam Ruditapes decussatus and its effect on bivalve behavior and physiology

The bivalve Ruditapes decussatus was evaluated as a possible biomonitor of heavy-metal contamination. Concentrations of copper (Cu), cobalt (Co), iron (Fe), nickel (Ni), and manganese (Mn) were measured in R. decussatus. Water and sediment samples were collected at two stations of Timsah Lake in Ismailia, Egypt, from October to November 2002, using atomic absorption spectrophotometry (AAS). Results from the heavy-metal and microbial analyses indicated that site II was less contaminated than site I. The bivalve showed accumulation of metals, with a bioaccumulation factor (BAF) greater than 4. The bioaccumulation of metals varied strongly according to the sampling site. After 48 h of depuration, Fe, Ni, Co, Cu, and Mn were reduced significantly, to 46.8% and 47.7%, 19.9% and 20.3%, 27.3% and 27.9%, 35.9% and 36.6%, and 18.2% and 26.6%, compared with the initial concentrations, in clam tissue at the two stations. In bivalves from site II the counts of total bacteria, fecal coliforms, and bacterial pathogens were reduced by more than 90%, whereas phage counts were only reduced by 56% after 4 days of depuration. The depuration of bivalves collected from the heavily polluted site (I) was not effective, as coliforms were reduced only by 85% after 4 days, whereas counts of pathogens and pathogenic indicators such as Vibrio, fecal Streptococcus, and coliphage decreased to less than 50% of the initial concentration. The time necessary to decrease contamination to 10%, 50%, and 90% for clams at both stations was consistently shorter for heavy metals than for microorganisms. Investigation of the effects of heavy-metal and microbiological depuration on valve movement and physiological rates (oxygen consumption and ammonia excretion) was carried out on R. decussatus to test the utility of physiological stress indices in assessing the health of depurated animals. Clams in the experimental tanks exhibited various states of activity, which were rated by identifying and scoring (0-4) the different parameters, including shell gap, siphon extension, and foot protrusion. Moreover, an increase in ammonia excretion was usually associated with an increase in respiration rate. The oxygen-to-nitrogen ratio provided a sensitive indicator of bivalve health. It can be concluded that shellfish monitoring and depuration data depended on the initial concentration of the pollutants. There were differences in the physiological responses of clams from the two sites during the periods of pre- and postdepuration of the contaminants. There was a significant correlation between reduction of metal concentration in clam tissue and enhancement of valve movement, as well as activity and increasing respiration rate.

Effects of depuration of molluscs experimentally contaminated with Escherichia coli, Vibrio cholerae 01 and Vibrio parahaemolyticus.

The aim of the present study was to investigate the behaviour of two pathogenic vibrios (Vibrio cholerae O1 and Vibrio parahaemolyticus) during depuration and to compare it with that of Escherichia coli, used as an indicator of suitability for consumption. Samples of Mytilus galloprovincialis were experimentally contaminated with E. coli, V. cholerae O1 and V. parahaemolyticus, depurated in a pilot plant using ozone and analysed at selected intervals. Numbers of E. coli and vibrios were estimated using an MPN method. The presence of vibrios was confirmed by the use of PCR. The target genes used were ctx for V. cholerae O1 and the restriction fragment pR72H for V. parahaemolyticus. There was a substantially smaller reduction in the numbers of both vibrios (approximately 1 log) during the depuration process than of E. coli (approximately 3 log). The results confirm the inadequacy of E. coli as an indicator that molluscs have been cleansed of other microbiological agents. The study confirms the risk associated with the consumption of mussels and the need to correctly conserve and cook them prior to consumption.