Bioavailability of heavy metals bound to sediments affected by a mining spill using Solea senegalensis and Scrobicularia plana

After the Aznalcóllar mining spill (April, 1998) different ecosystems along the Guadiamar river and the Guadalquivir estuary were impacted by high concentrations of metals. The concentration of metals Zn, Cd, Pb, Cu and As has been detected as a good tracer of the pathway of the toxic spill. Different individuals of the fish Solea senegalensis and the clam Scrobicularia plana were exposed to contaminated sediments after the accidental spill in the south-west Spain. The induction of metallothioneins in fish and the bioaccumulation of metals in clams were determined in different tissues to determine the biological adverse effect associated with the heavy metals from the spill. A relationship between the enrichment of metals in the tissues and the induction of metallothioneins was determined for those assays performed using contaminated sediments. The bioaccumulation of metals indicates that the risk associated with the spill should be continuously evaluated to establish the sublethal effects related to the accident.     

The effects of the ‘Braer’ oil spill, Shetland Isles, Scotland, on P4501A in fanned Atlantic salmon (Salmo salar) and the common dab (Limanda limanda)

This paper describes the response of two fish species, the Atlantic salmon (Salmo salar) and the common dab (Limanda limanda) to the oil spilled from the Braer tanker which grounded on the southern tip of Shetland, Scotland, on 5 January 1993. Both the immediate sublethal effects and the long-term response to the oil which accumulated in sediments around the Shetland Isles, Scotland, are examined. The primary response measured was the induction of detoxification enzymes and the relationship of the levels or activities of these enzymes to the concentration and distribution of aromatic hydrocarbons measured in sediments, water and fish. The results show that, immediately following the spill, there was a marked induction of Cytochrome P4501A enzymes in salmon, indicative of exposure to bioavailable aromatics. In dab there was evidence of induction at some sites in January 1993 immediately following the spill but, subsequently, no induction has been observed in fish caught in the vicinity of Shetland despite the very high concentrations of oil measured in sediments at some locations. This would indicate that the polyaromatic hydrocarbons in these sediments are unlikely to be directly bioavailable to fish. The effect of the oil spill on hepatic pathology in dab was investigated and shows that pathology predictive of neoplasia, such as basophilic foci and vacuolation, were observed in fish from the most contaminated sites in 1994 but not in 1993. The incidence of this pathology appeared to correlate with the degree of contamination at the sites, but additional studies are required to establish whether this was a consequence of the initial impact and exposure from waterborne oil at the time of the spill or whether it was due to the continued exposure to oil from the sediments.     

Regulation of Tilapia metallothionein gene expression by heavy metal ions

Tilapia is a common fish species inhabiting inland waters and estuarine regions in Hong Kong and Southeast Asia, and useful for bio-monitoring of metal pollution. Metallothionein (MT) gene expression in fish tissues has been useful to sub-lethal risk assessment as biomarker of exposure to metal ions in fishes inhabiting metal contaminated area. To investigate metal inductions of Tilapia MT gene expression in vivo, Tilapias were injected with different concentrations of heavy metals and tissues were then removed for quantitative PCR assay using mimic PCR methods. All of the metal ions tested (Cu²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Pb²⁺ and Zn²⁺) were able to induce hepatic MT mRNA levels. Renal MT mRNA levels of Cd²⁺ and Zn²⁺ treated fish was not induced with significant fold induction, however MT mRNA levels in gills were sensitive to the administrations of these metal ions. These data indicated that Tilapia MT mRNA levels in gills and liver are sensitive biomarker of exposure to various metal ions.     

钦州湾桐花树群落沉积物及植物体中重金属元素累积与分异研究

Mangrove wetlands can reduce heavy metal pollution by trapping heavy metals. In this study, the concentration,transport and bioaccumulation of Cr, Cd, Cu, Zn and Pb in the sediments and different parts of Aegiceras corniculatum at four different sites in the Qinzhou Bay in southwestern China were investigated. The results showed that although the potential ecological risk of all five heavy metals was slight, the concentration of Cr was at a moderate pollution level due to the emissions of industries and aquaculture waste water. Core sediment records indicated that the concentrations of heavy metals at the depth of 0–20 cm were relatively high, showing an increasing trend of heavy metals over the past 20–30 years. Cr, Cu, Pb and Cd accumulated mainly in the roots of A. corniculatum, while Zn accumulated mainly in the stems. Aegiceras corniculatum showed the strongest transport capacity for Zn and Cu and the strongest bioaccumulation ability for Cd. Compared with other mangrove communities, A. corniculatum can be chosen as a restoration species in tropical and subtropical coastal zones polluted by Zn, Cu and Cd.     

Altered glutathione status in atlantic croaker (Micropogonias undulatus) tissues exposed to lead

Metals which induce the synthesis of metallothioneins, such as cadmium and mercury, also elevate glutathione (GSH) concentrations in fish tissues.^1,2 To determine whether metals which do not stimulate metallothionein synthesis increase GSH levels, the GSH status of Atlantic croaker tissues was examined after oral administration of lead. Lead significantly increased GSH levels in the intestine and liver, but not in kidney or brain tissues. Lead was not bound to GSH and the increase in GSH did not appear to be linked to lead accumulation in these tissues. Investigations of hepatic GSH synthesis and turnover in vitro using a radiolabelled amino acid precursor, C¹⁴ glycine, showed that the elevation of GSH was due to an increase in GSH synthesis rather than decreased utilization of GSH. These studies suggest that the interactions between GSH and lead are indirect and involve a stimulatory effect of the metal on the activity of the enzymes for GSH synthesis.     

A laboratory and field comparison of sediment polycyclic aromatic hydrocarbon bioaccumulation by the cosmopolitan estuarine polychaete Streblospio benedicti (Webster)

Polycyclic aromatic hydrocarbon (PAH) bioaccumulation by the polychaete worm Streblospio benedicti (Webster) was measured under exposure to PAH-contaminated sediments in the field and for 28 d in the laboratory. Streblospio benedicti collected from field sediments contaminated at 2.94, 1.07, and l.52 μg g⁻¹ fluoranthene (FLU), benz[a]anthracene (BAA), and benzo[a]pyrene (BAP), bioaccumulated those PAHs at 1.53, 0.215, and 0.332 μg g⁻¹, while worms isolated from less contaminated field sediments (0.399, 0.228, 0.288 μg g⁻¹ FLU, BAA, and BAP) had FLU, BAA, and BAP body burdens of 0.543, 0.236, and 0.083 μg g⁻¹. Worms incubated for 28 d in PAH-spiked sediments (1.52, 0.991, 0.504 μg g⁻¹ FLU, BAA, and BAP) bioaccumulated those PAHs at 0.382, 0.966, and 0.602 μg g⁻¹, respectively. Data normalization to organism lipid and sediment organic carbon (biota-sediment accumulation factors [BSAFs] strongly suggest that Streblospio PAH bioaccumulation was directly related to percent sediment organic carbon, but BSAFs were substantially lower than predicted by equilibrium partitioning theory. BSAFs decreased with increasing PAH log K_ow, in worms collected from field sediments, but in spiked sediments BSAFs increased with increasing PAH hydrophobicity. This disparity may have been caused by insufficient spiked-sediment equilibration time (1.5h) in the case of the laboratory test sediments.     

Etude du transfert de quelques oligo-éléments métalliques entre le milieu sédimentaire estuarien et les poissons plats ‘mangeurs de sédiments’

In order to study the transfer of trace metals (Cd, Pb, Cu, Zn) between sediments and living organisms, flatfishes (flounder, Platichthys flesus and sole, Solea solea) were collected monthly in the Loire estuary (France) for more than a year. Trace metal concentrations were determined in flatfish digestive contents and tissues. The influence of some ecological factors upon bioaccumulation of trace metals was considered.We consider the benthic way of life not to be responsible for a preferential bioaccumulation of trace metals in flatfishes. Although zinc accumulation in external organs is important, the hypothesis of an uptake via food and sediment cannot be rejected.     

Selenium in sediments, pore waters and benthic infauna of Lake Macquarie, New South Wales, Australia

Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a significant source of selenium in the lake's food web. Analysis of surficial sediment samples indicated higher selenium concentrations near what are believed to be the main industrial sources of selenium to the lake: a smelter and a power station. Sediment cores taken from sediments in Mannering Bay, near a power station at Vales Point, contained an average of 12 times more selenium in surficial sections than sediment cores from Nord's Wharf, a part of the lake remote from direct inputs of selenium. The highest selenium concentration found in Mannering Bay sediments (17.2 μg/g) was 69 times the apparent background concentration at Nord's Wharf (0.25 μg/g). Pore water concentrations in Mannering Bay were also high, up to 5 μg/l compared to those at Nord's Wharf which were below detection limits (0.2 μg/l). Selenium concentrations in muscle tissues of three benthic-feeding fish species (Mugil cephalus, Platycephalus fuscus, Acanthopagrus australis) were significantly correlated (p<0.05) with surficial sediment selenium concentration. Selenium concentrations in polychaetes and molluscs of Mannering Bay were up to 58 times higher than those from Nord's Wharf. Two benthic organisms, the eunicid polychaete Marphysa sanguinea and the bivalve mollusc Spisula trigonella, were maintained at different densities in selenium-spiked sediments. Both animals accumulated selenium from the spiked sediment, confirming that bioaccumulation from contaminated sediments occurs. Collectively, these data suggest that benthic food webs are important sources of selenium to the fish of Lake Macquarie.     

Histopathological changes in the liver of dab (Limanda limanda) from a contamination gradient in the North sea

As part of a joint workshop organised by the International Council for the Exploration of the Sea (ICES) and the Intergovernmental Oceanographic Commission (IOC) on biological effects monitoring techniques. dad (Limanda limanda) were examined from six spaced stations along a 200 km transect extending from near the mouth of the Elbe River out to the Dogger Bank in the North Sea. Based on historical data, differences in contaminant concentrations in sediments exist along the transect (lipophilic organic xenobiotics at the inshore sites and heavy metals offshore over the Dogger Bank). The most contaminated site sampled was the most inshore, the least contaminated was approximately midway along the transect, with contamination building up again over the farthest point along the transect, over the Dogger Bank. Multiple organs and tissues were examined for full pathology from each fish sampled. Only liver data are presented here (11–20 livers per station). The most significant lesions were considered to be well-developed foci of cellular alteration, high mitotic activity and high neutral lipid accumulation in livers from dab sampled from the most inshore site examined. Livers from the least-contaminated station showed minimal evidence of such changes. Foci of cellular alteration and neutral lipid accumulation were also seen in dab liver sampled from fish from the Dogger Bank site. Thus far, the hepatic changes seen correlate well with the most contaminated sites along the transect. The value of comprehensively examining the histopathology of an organ of toxicological significance, such as the liver in a European species of flatfish, is demonstrated.     

Tapes philippinarum seed exposure to metals in polluted areas of the Venice lagoon

The concentration changes of 12 metals (As, Hg, Cd, Cr, Co, Cu, Pb, Mn, Ni, V, Zn, Fe, and Hg) in the soft tissues of Tapes philippinarum during growth were investigated. Clams were seeded in two contaminated areas of the Venice lagoon (San Giuliano and Fusina) and in an area of the Marano lagoon (Lignano Sabbiadoro) close to the clam-farm where the seed was produced. Metal trends were very different according to the considered element, the study site and the growth period.Arsenic was always higher in clam tissues than in surface sediments and suspended particles in all the three stations. Mercury, Cd and Cu were higher in the clams from Marano and Fusina but not in those from San Giuliano. Zinc and Co in clams exceeded the concentrations in the sediment and suspended particles only at Marano. The other elements (Cr, Pb, Mn, Ni, and Fe) were always higher in SPM and sediments. In general metal concentrations in clams were more highly correlated to concentrations in the suspended particles rather than in the surface sediments and in suspended clams rather than in bottom clams, nevertheless significant differences between stations and contaminants were found. Metal concentrations in clams were always lower than the European regulatory limits.     

Biomarker responses in Macoma nasuta (Bivalvia) exposed to sediments from northern San Francisco Bay

Our study investigates biomarker responses and survival of Macoma nasuta exposed to sediments collected from six locations in northern San Francisco Bay. Biomarkers analyzed were stress proteins (hsp70) in gill, mantle and digestive gland, lysosomal membrane damage and histopathologic lesions. Sediments and clam tissues were analyzed for a comprehensive suite of heavy metals and trace organic pollutants. Sediment grain size and organic carbon content were determined. Clams accumulated metals, polyaromatic hydrocarbons (PAHs) and organochlorine pesticides (aldrin and p,p^′-DDT and its metabolites p,p^′-DDD and p,p^′-DDE). Pearson and Spearman correlation analysis revealed that mortality, hsp70 in gill and histopathologic lesion scores in gonads, and lysosomal membrane damage were significantly correlated with tissue concentrations of DDT and/or its metabolites. Tissue concentrations of metals, in particular nickel, chromium, and copper, were associated with macrophage aggregates in digestive gland and germ cell necrosis. Cadmium was linked to mortality and lysosomal membrane damage.     

可口革囊星虫与其栖息地底泥中的重金属含量及相关性分析

用原子吸收光谱法(AAS)和原子荧光光度法(AFS)测定了采集于北海银滩镇、厦门海门岛、宁德漳湾镇、乐清西门岛、温岭坞根镇、三门花桥镇等地区自然滩涂以及温岭坞根镇养殖区的可口革囊星虫(Phascolosoma esculentas)及其栖息地的底泥样品中Zn、Cu、Mn、Fe、Cd、Pb、Hg 和As 等8 种重金属含量, 并对检测结果进行了含量特征、生物体与栖息地底泥中重金属含量相关性分析、生物体重金属富集系数分析。结果表明: 不同栖息地可口革囊星虫间的重金属含量差异性显著(P<0.05), 各群体中Pb 含量均超过标准, 厦门海门岛群体中Cd 含量超标; 厦门海门岛、乐清西门岛自然滩涂栖息地和温岭坞根镇养殖区等底泥中重金属含量相对较高, 所有采样点底泥中Cu 含量以及乐清西门岛自然滩涂底泥中Cd 含量达到沉积物质量标准Ⅱ类; 可口革囊星虫对Zn、Cu、Fe 的富集系数均小于1, 对Mn、Cd、Pb、Hg 和As 的富集系数均大于1。Zn、Cu、Fe、Pb 和As 的富集系数在大部分群体间差异性较小; 可口革囊星虫中的Fe 和As 含量与底泥中的Fe 和As 含量高度正相关, Zn 和Hg 含量的相关性次之, 其余重金属元素含量的相关性较差。     

Relevance of intracellular partitioning of metals in prey to differential metal bioaccumulation among populations of mummichogs (Fundulus heteroclitus)

Intracellular partitioning of trace metals is critical to metal tolerance in aquatic organisms and may also influence metal trophic transfer in ecosystems. In this study, we tested the relevance of metal (Cd, Cu, Pb, and Zn) intracellular partitioning in prey as an indicator of metal trophic availability to benthic forage fish, mummichogs (Fundulus heteroclitus), in chronically metal-polluted salt marshes in New York, USA. Two common prey of mummichogs in the study area, Palaemonetes pugio and Nereis acuminata, generally stored increasingly higher proportions of non-essential metals (particularly Pb) in insoluble (less trophically available) cellular components, as the whole body burdens increased. In contrast, intracellular partitioning of essential metals (Cu and Zn) in invertebrate prey varied relatively little among sites. Differential Cd and Pb intracellular partitioning patterns within P. pugio among sites were significantly associated with Cd and Pb whole body burdens in mummichogs, respectively (i.e., prey-driven bioreduction of metals), while bioaccumulation of Cu and Zn in mummichogs was similar among populations. The findings in this study suggest that metal intracellular partitioning within prey may be partially responsible for metal trophic availability to a predator in metal-polluted habitats, while there was also evidence that some predator-dependent processes may offset differential trophic availabilities from prey.     

Influence of chronic exposure to silver and mercury in the field on the bioaccumulation potential of the bivalve Macoma balthica

In order to assess the adaptation to metals previously observed in the bioindicator organism, Macoma balthica, subjected to chronic contamination by silver and mercury in the French Loire estuary, the bioaccumulation potential of individual organisms originating from the contaminated Loire estuary and a relatively uncontaminated control estuary (Somme) was evaluated using both radiotracers and stable isotopes of Ag (80 μg Ag litre⁻¹) and Hg (100 μg Hg litre⁻¹). Clams from the contaminated estuary were more sensitive to Ag (LT₅₀ = 9d) than those originating from the Somme estuary (LT₅₀ > 15d), even though the former bioaccumulated Ag to a significantly lower degree. This is attributed to a consequence of the chronic stress induced by Ag while clams were living in their natural environment. Therefore, past history of trace metal contamination should be considered when evaluating the susceptibility of M. balthica to heavy metal exposure. Lower uptake rates obtained for Hg (during the initial uptake phase only) and for Ag in clams from the polluted estuary suggest the presence of an adaptive trait for survival in contaminated areas. However, the lower degree of bioconcentration observed for Ag was not sufficiently low to reduce the sensitivity of the organisms to Ag and allow them to resist the toxic stress. Clams that survived Ag or Hg exposure at LT₅₀ did not protect themselves against metal toxicity by accumulating a significantly lesser amount of these metals than clams which did not survive metal stress. The results suggest that the bioaccumulation potential of each individual was not a factor which can explain the survival ability of M. balthica exposed to chronic Ag and Hg contamination in estuaries. In this case, cellular, biochemical and genetic levels of adaptation are presumed to be of greater importance.     

Monitoring of the chemical pollution of the river Rhône through measurement of DNA damage and cytochrome P4501a induction in chub (Leuciscus cephalus)

The in vivo response of freshwater fish exposed to pollutants was assessed using two biomarkers, 7-ethoxyresorufin-O-deethylase (EROD) induction and DNA single strand breaks. Chub (Leuciscus cephalus) were caught in spring and in fall at various locations in the river Rhône watershed. EROD activity was measured in the liver while DNA damage was evaluated in chub erythrocytes using the recently developed Comet assay. Chemical contamination was evaluated both in fish muscle (PCBs) and in sediment (PCBs, PAHs, heavy metals) collected at each sampling station. Sex of individuals was shown to influence the level of EROD activity but not the level of DNA damage. The EROD activity as well as the DNA damage were found to be higher in the mostly contaminated stations compared to the reference one. This study shows that multibiomarker-based approach provides complementary informations about early effects in feral fish exposed to complex chemical pollution and highlights the interest of the Comet assay in genotoxicity assessment.     

Bioavailability and effects of sediment-bound TBT in deposit-feeding clams, Scrobicularia plana

Concentrations of tributyltin (TBT), dibutyltin (DBT), inorganic and total tin have been measured in water, sediments and deposit feeding clams, Scrobicularia plana, from 25 estuarine locations in England and Wales, in order to compare the bioavailability of different forms of the element. Abnormally high tin values in Scrobicularia from harbours and areas of high boating activity testify to the high bioaccumulation potential of organotins, notably TBT derived from anti-fouling paints, relative to inorganic tin.Infaunal deposit-feeding bivalves consistently contain higher concentrations of TBT than other benthic organisms indicating that sediments may be an important route for uptake. Significant correlations between sediment TBT values and residues in clams such as S. plana (r = 0·81, p < 0·001) support this hypothesis. Direct evidence of the bioaccumulation of sediment-bound TBT is provided from laboratory experiments in which Scrobicularia were exposed to TBT in water and in sediments, either separately or in combination. The results of these experiments clearly demonstrate a predominantly particulate component for TBT uptake in clams.The kinetics of TBT accumulation and elimination were studied in Scrobicularia exposed to sediments containing 0·3 and 1·0 μg/g TBT (as tin). Equilibrium concentrations in tissue are approached after 40 days.Sediments containing 10 μg/g TBT are acutely toxic to S. plana, although such concentrations are only likely to occur close to dockyards and large marinas. Preliminary laboratory and field observations suggest however, that clam populations could be affected at TBT concentrations in sediments of 0·3 μg/g and possibly lower.     

GFP标记的迟缓爱德华菌感染诸氏鲻虾虎鱼后组织分布研究

为探讨迟缓爱德华菌(Edwarsiellatarda)入侵途径,建立感染模型,作者通过电转化法构建GFP标记的迟缓爱德华菌EtMc1512(质粒PMDpp-EGFP),实验设立浸泡组、腹腔注射组和肌肉注射组,感染后采集各组实验诸氏鲻虾虎鱼(Mugilogobius chulae)血液、鳃、肝脏、肠、肌肉,培养法统计分析各组织中的荧光细菌数;浸泡组取样时间为0、2、4、6、8、12、24 h,腹腔注射组和肌肉注射组取样时间为6、12、24、48、72、96h。结果显示,构建的EtMc1512-GFP具有较强荧光,GFP标记前后菌株毒力基因(citC、mukF、esrB、katB、fimA、gadB)检测结果均为阳性。浸泡感染后实验鱼各组织内的荧光菌随时间表现为先升后降的趋势,最高菌量出现在肠道(2.51×106CFU/g),其次为鳃(4.19×104CFU/g)、血液(1.65×104CFU/g),肠道荧光菌显著高于其他组织(P0.05);腹腔注射感染后肝脏(4.55×106CFU/g)和血液(4.65×106CFU/g)菌量最高;肌肉注射感染后肌肉在48h首先检出荧光菌,血液(2.93×104 CFU/g)菌量最高。结果表明,肠道、肝脏和肌肉分别是迟缓爱德华菌浸泡感染、腹腔注射感染和肌肉注射感染诸氏鲻虾虎鱼的主要组织器官,在自然条件下迟缓爱德华菌经口感染诸氏鲻虾虎鱼风险较高。     

Petroleum contamination and biochemical alterations in oysters (Crassostrea gigas) and plaice (Pleuronectes platessa) from bays impacted by the Amoco Cadiz crude oil spill

Following the Amoco Cadiz crude oil spill in March 1978, marine animals in coastal and estuarine environments along the north shore of Brittany, France became heavily contaminated with crude oil. The resident benthic fauna in the oil-impacted area which survived the spill were severely stressed by the pollution. The objectives of our investigation were to document long-term trends in petroleum hydrocarbon contamination and sublethal stress in oysters and plaice from the estuaries, Aber Benoit and Aber Wrac'h. Oysters in the estuaries accumulated aliphatic and aromatic petroleum hydrocarbons to high levels and remained heavily contaminated for the duration of the 27 month investigation. Plaice, on the other hand, retained only low concentrations of petroleum hydrocarbons in muscle and liver tissue. Nevertheless, the oysters exhibited very few histopathologic and biochemical responses to the oil, whereas the plaice from the estuaries exhibited a variety of sublethal histopathologic and biochemical alterations.     

CYP1A- and CYP3A-immunopositive protein levels in digestive gland of the mussel Mytilus galloprovincialis from the Mediterranean Sea

CYP1A-immunopositive protein can be elevated in response to planar PAHs and PCBs in Mytilus sp. digestive gland whilst CYP3A-immunopositive protein has been associated with testosterone 6β-hydroxylation in fish. Levels of CYP1A- and CYP3A-immunopositive protein were determined in Mytilus galloprovincialis digestive gland microsomes collected from 12 sites in the Mediterranean Sea during May and September 2001. CYP1A-immunopositive protein was significantly highest at contaminated sites whilst CYP3A-immunopositive protein was significantly lowest. A weak negative correlation (r²=0.21) was seen between CYP1A- and CYP3A-immunopositive protein. Little evidence of differences at the different sampling times was observed. These results confirm previous work indicating elevation of CYP1A-immunopositive protein in Mytilus sp. digestive gland at contaminated sites. Further study is required to characterise CYP3A-like expression in Mytilus and to elucidate the consequences of possible CYP3A-like down-regulation at contaminated sites.     

A description of chloride cell and kidney tubule alterations in the flatfish Solea senegalensis exposed to moderately contaminated sediments from the Sado estuary (Portugal)

The effects of sediment-bound contaminants on kidney and gill chloride cells were surveyed in juvenile Solea senegalensis exposed to fresh sediments collected from three distinct sites of the Sado Estuary (Portugal) in a 28-day laboratorial assay. Sediments were analyzed for metallic contaminants, polycyclic aromatic hydrocarbons and organochlorines as well as for total organic matter, redox potential and fine fraction. The potential for causing adverse biological effects of each surveyed sediment was assessed by comparison of contaminant levels to available guidelines for coastal sediments, namely the Threshold Effects Level (TEL) and the Probable Effects Level (PEL). The Sediment Quality Guideline Quotient indices (SQGQ) were calculated to compare the overall contamination levels of the three stations. A qualitative approach was employed to analyze the histo/cytopathological traits in gill chloride cells and body kidney of fish exposed to each tested sediment for 0, 14 and 28 days. The results showed that sediment contamination can be considered low to moderate and that the least contaminated sediment (from a reference site, with the lowest SQGQ) caused lesser changes in the surveyed organs. However, the most contaminated sediment (by both metallic and organic xenobiotics, with highest SQGQ) was neither responsible for the highest mortality nor for the most pronounced lesions. Exposure to the sediment presenting an intermediate SQGQ, essentially contaminated by organic compounds, caused the highest mortality (48%) and the most severe damage to kidneys, up to full renal necrosis. Chloride cell alterations were similar in fish exposed to the two most contaminated sediments and consisted of a pronounced cellular hypertrophy, likely involving fluid retention and loss of mitochondria. It can be concluded that sediment contamination considered to be low or moderate may be responsible for severe injury to cells and parenchyma involved in the maintenance of osmotic balance, contributing for the high mortality levels observed. The results suggest that sediment-bound organic contaminants such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls) may be very toxic to the analyzed organs, especially the kidney, even when present in low-risk concentrations.