Mercury bioaccumulation in the spotted dogfish (Scyliorhinus canicula) from the Atlantic Ocean

The annual and life-cycle mercury bioaccumulation pattern in selected tissues of the economically relevant Elasmobranchii species Scyliorhinus canicula was studied, and the risks associated with its consumption evaluated. Preferential mercury bioaccumulation occurred in muscle tissue, and followed the order muscle>heart>liver>gills>pancreas. Total mercury in muscle tissue ranged from 0.13mgkg(-1) (wwt) in 1+year old males to 0.8mgkg(-1) (wwt) in 8+ year old mature females, with no significant differences found between genders, and no clear lifespan bioaccumulation pattern observed, except for mature females. Organic mercury in the muscle ranged from 0.05mgkg(-1) (wwt) to 0.52mgkg(-1) (wwt), corresponding to an average of 70% of total mercury content. In mature females, a significant correlation (R=0.99, P=0.01) was found between size and organic mercury fraction, suggesting reproduction as an important factor controlling organic mercury bioaccumulation in the spotted dogfish.

Water-soluble fraction of mercury, arsenic and other potentially toxic elements in highly contaminated sediments and soils

The water-soluble contents of mercury, arsenic and other potentially toxic elements in highly contaminated sediment and soil samples from Portugal were determined. Mercury and arsenic concentrations were detectable and reproducible among replicate experiments. Despite the acidic pH, the low organic carbon content and the exceptionally high levels of contamination of certain samples (total mercury contents varied between 0.15 and 3180 mg kg(-1) while total arsenic concentrations ranged from 11 to 6365 mg kg(-1)), the water-soluble percentages of both mercury (<1.2%) and arsenic (<4.6%) were generally low. The variability of the water-soluble fractions of these two elements among these samples and at the occurring pH conditions seems not to be associated with the release of other potentially toxic elements. The highest water-soluble concentrations of the remaining potentially toxic elements were generally observed in the 15-25 cm depth layer of sediments from areas colonised with plants (Halimione portulacoides) and in mining soil samples. Zinc, cobalt, copper and cadmium showed the highest water-soluble percentages of elements in relation to total metal contents. Given the high contamination levels, the availability of potentially toxic elements in these areas as well as possible risks to the environment and humans should be further investigated. The presence of plants (H. portulacoides) appears to cause significant changes in the sediment matrix that increase the mobility of several potentially toxic elements, particularly in the 15-25 cm depth layer. The effects of vegetation on the fractionation of potentially toxic elements on these sediments should be further studied.

Contribution of primary producers to mercury trophic transfer in estuarine ecosystems: possible effects of eutrophication

There is an ongoing eutrophication process in the Ria de Aveiro coastal lagoon (Portugal), with progressive replacement of rooted primary producers for macroalgae. Taking advantage of a well-defined environmental contamination gradient, we studied mercury accumulation and distribution in the aboveground and the belowground biomass of several salt marsh plants, including the seagrass species Zostera noltii and the dominant green macroalgal species Enteromorpha sp. The results of these experiments were then placed into the context of the estuarine mercury cycle and transport from the contaminated area. All salt marsh plants accumulated mercury in the root system, with Halimione portulacoides showing the highest levels, with up to 1.3 mg kg(-1) observed in the most contaminated area. Belowground/aboveground ratios were generally below 0.4, suggesting that salt marsh plants are efficient immobilizers and retainers of mercury agents. Moreover, due to their sediment accretion capacities, salt marsh plants seem to play an important role in the sequestration of mercury in estuarine sediments. Seagrasses, on the other hand, accumulated considerable amounts of mercury in the aboveground biomass with belowground/aboveground ratios reaching as high as 1.4. These results may be due to their different routes of uptake (roots and foliar uptake) which suggests that seagrass meadows can be an important agent in the export of mercury from contaminated areas, considering the high aboveground biomass replacement rates. Rooted macrophytes accumulate less mercury in their aboveground biomass than macroalgae. The change of primary producer dominance due to eutrophication can originate a 4- to 5-fold increase in primary producer associated mercury. This mercury would be available for export, making it bioavailable to estuarine food webs, which stresses the need to reverse the current eutrophic status of estuarine systems.

Mercury pollution in Ria de Aveiro (Portugal): a review of the system assessment

The Ria de Aveiro (Portugal) is a coast al lagoon adjacent to the Atlantic Ocean and it has an inner bay (Laranjo bay) that received a highly contaminated effluent discharged by a mercury cell chlor-alkali plant from the 1950s until 1994. The aim of this study is to review in a holistic way several research studies that have been carried out in the Ria de Aveiro, in order to evaluate the remobilization of the mercury accumulated within the system and the recovery of the lagoon. The spatial distribution of the total mercury in the surrounding terrestrial environment has also been considered. Results indicate that the main mercury contamination problems in the Ria de Aveiro are confined to the Laranjo bay. Mercury export to the coastal waters and its impact on the nearshore compartments (water column, sediment and biota) are low. No direct effects of the mercury from nearby industrial activities were detected in Aveiro's urban soils, although historical mercury contamination is still affecting soil quality in the immediate vicinity of the chlor-alkali plant, located in Estarreja. Moreover, macrophyte harvesting for human direct or indirect use and the consumption of mussels, crabs and the sea bass from the Laranjo bay may constitute a health risk. Further studies focusing on developing skills for the restoration of the ecosystem are presently underway.

A review of regulatory decisions for environmental protection: part I - challenges in the implementation of national soil policies

Since many soil studies have already revealed the possible risks to human health and the environment arising from contaminated soils it is therefore crucial to preserve soil quality under current and future conditions. In the last three decades a number of countries already introduced national policies and practices for the management of contaminated sites, and in 2002, an EU Thematic Strategy for Soil Protection was proposed by the European Commission. In this paper we review and analyse several national contaminated land policy regimes already in place in order to assess common elements and to identify specific needs in the development of national soil policies. We propose a framework that combines the D-P-S-I-R structure of policy evaluation with the Source-Pathway-Receptor approach to health risk assessment to support the development of effective country specific regulatory decisions for managing contaminated land in countries where these are yet to be implemented. The framework proposed allows decision makers to effectively use available information and to identify existing data gaps. As a result it is apparent that while there are technical aspects of site characterisation, risk assessment and remediation processes that could be commonly implemented at an EU level there are certain trans-scientific aspects that require political choices and need to be customized by EU Member States.

Sensitivity of young rats to nicotine exposure: Physiological and biochemical parameters

This work has investigated the effects of prolonged exposure of young rats to nicotine on some physiological and biochemical parameters. Wistar male rats (30 days old) were treated (s.c.) with saline or nicotine 5mg/kg/day for 28 or 56 days. They received five injections (1mg/kg) per day (8, 10, 12:00 a.m., 2 and 4:00 p.m.) on the dark period of the cycle. Nicotine exposure for 56 days reduced body and liver weights. Moreover, nicotine exposure for 28 or 56 days decreased the hepatic glycogen but not blood glucose levels. The activities of blood and hepatic PBG-synthase, and blood and cerebral acetylcholinesterase were not affected by in vivo exposure. However, these activities were inhibited by nicotine in vitro. Results show that although high levels of plasma cotinine were found in both intervals of exposures, the parameters here analyzed were not affected by prolonged nicotine exposure except the storage of glucose, and body and liver weights.

A review of regulatory decisions for environmental protection: part II - the case-study of contaminated land management in Portugal

This paper provides a case-study analysis of the challenges in the implementation of national soil policies, which was developed by the authors in Part I of the review of regulatory decisions for environmental protection [Rodrigues SM, Pereira ME, Ferreira da Silva E, Hursthouse A, Duarte AC. A review of regulatory decisions for environmental management: Part I-challenges in the implementation of national soil policies. Environ Int 2009. doi:10.1016/j.envint.2008.08.007]. The Portuguese case was selected as a case-study since specific regulatory decisions for contaminated land management are still in the early stages of development. Given the gap between the situation at the EU level and the state of Portuguese soil policy development, it is of merit to consider national contaminated land policy regimes already in place within the EU and to see if these provide a suitable basis to define the main challenges and research needs for the implementation of a Portuguese contaminated land management strategy. A framework combining the D-P-S-I-R (drivers-pressures-sources-impacts-responses) structure of policy evaluation with the Source-Pathway-Receptor approach to health risk assessment is proposed to derive an effective regulatory framework for managing contaminated land in Portugal, using available information and only to develop new data and research where knowledge gaps exist. Funding site clean-up and assigning liability were identified as relevant factors currently hampering site remediation. Most relevant research needs for the development of contaminated land management practices in Portugal are those associated to the definition of a risk assessment framework and setting guidelines for the evaluation of risks posed to both humans and ecosystems. Other relevant and innovative features are the integration of soil function analysis into site investigations and the definition of a framework that combines risk assessment with soil function analysis. The analysis of the Portuguese case also provides insight into the discussions needed for the effective development of regulatory decisions for contaminated land management in countries with no history of implementing specific soil policies.

Oviduct adenocarcinoma in some species of captive snakes

This article reports 5 cases of oviduct adenocarcinoma in adult captive snakes from Smithsonian's National Zoological Park. This neoplasm was found in 1 of each of the following species: emerald tree boa (Corallus caninus), Amazonian tree boa (Corallus enydris enydris), Burmese rock python (Python molurus bivittatus), Northern pine snake (Pituophis melanoleucus melanoleucus), and corn snake (Elaphe guttata). Grossly, tan to red firm masses were found within oviducts in 3 cases. In an additional 2 cases, the primary tumor was detected only histologically. Microscopically, neoplasms were papillary, and often extended transmurally. The neoplastic cells were polygonal and organized in acini or cords, with often abundant fibrovascular stroma. Hemorrhages and necrosis were present in all cases. Inflammation, myxomatous material, desmoplasia, and bacteria were often observed. Histologic evidence of metastasis was present in all cases. Solid metastases were seen in all animals except the Northern pine snake and involved several organs including the liver, lung, and heart. Emboli of neoplastic cells were observed in all animals but the Burmese rock python and corn snake.

Mercury in salt marshes ecosystems: Halimione portulacoides as biomonitor

Mercury concentrations were quantified in Halimione portulacoides (roots, stems and leaves) as well as in sediments from eight Portuguese estuarine systems, covering seventeen salt marshes with distinct degrees of mercury contamination. The concentration of mercury in the sediments ranged from 0.03 to 17.0 microg g(-1). The results show that the accumulation of mercury differed according to the organ of the plant examined and the concentration of mercury in the sediments. Higher mercury concentrations were found in the roots (up to 12.9 microg g(-1)) followed by the leaves (up to 0.12 microg g(-1)), while the stems had the lowest concentrations (up to 0.056 microg g(-1)). A linear model explained the relation between the concentrations of mercury in the different plant organs: roots and stems (R(adj)(2)=0.75), stems and leaves (R(adj)(2)=0.85) and roots and leaves (R(adj)(2)=0.78). However, the results show that the variation of mercury concentration in the roots versus mercury concentration in the sediments was best fitted by a sigmoidal model (R(adj)(2)=0.89). Mercury accumulation in the roots can be described in three steps: at a low range of mercury concentrations in the sediments (from 0.03 up to 2 microg g(-1)), the accumulation of mercury in roots is also low reaching a maximum concentration of 1.3 microg g(-1); the highest rates of mercury accumulation in the roots occur in a second step, until the concentrations of mercury in the sediments reach approximately 4.5 microg g(-1); after reaching this maximum value, the rate of mercury accumulation in the roots slows down leading to a plateau in the concentration of mercury in the roots of about 9.4 microg g(-1), which corresponds to a mercury concentration in the sediments of about 11 microg g(-1). A linear model explained also the accumulation of mercury in leaves versus the mercury concentration in the sediments (R(adj)(2)=0.88). Differences in responses of roots and leaves are explained by the dynamics of the plant organs: old roots are mineralised in situ close to new roots, while leaves are renewed. Previous studies have already shown that H. portulacoides is a bioindicator for mercury and the results from this work sustain that H. portulacoides may also be used as a biomonitor for mercury contamination in salt marshes. Nevertheless, caution should be taken in the application of the models, concerning the life cycle of the species and the spatial variability of the systems.

The macrobenthic community along a mercury contamination in a temperate estuarine system (Ria de Aveiro, Portugal)

Mercury is a widely distributed environmental pollutant and a toxic element to all living organisms. This study represents an attempt to evaluate its correlation with the macrobenthic community structure in a temperate estuarine system, the Ria de Aveiro (Portugal). The macrobenthic community structure showed significant differences along the mercury gradient. Overall, the increase of mercury contamination was associated with reduced total abundance, lower species richness, and dominance of tolerant taxa. The polychaetes Hediste diversicolor and Alkmaria romijni, and the isopod Cyathura carinata were associated with high levels of mercury in sediment, while the bivalves Scrobicularia plana, Cerastoderma edule and Abra alba showed higher density in lesser contaminated sites. Furthermore, highly contaminated sites showed substantially lower abundances of surface-deposit feeders and herbivores, and higher abundances of subsurface-deposit feeders and omnivores. Salinity was also a significant factor affecting the community, being responsible for seasonal variations in the macrobenthic assemblages.

Mercury mobility in a salt marsh colonised by Halimione portulacoides

The present study intends to increase the knowledge on the mobility of mercury in a salt marsh colonised by Halimione portulacoides. Mercury distribution in the sediment layers and its incorporation into the plant biomass were assessed, as well as the potential export of mercury from the contaminated area to the adjacent environment. Mercury pools in the sediments ranged from 560 to 943 mg m(-2) and are largely associated with the solid fraction, with just a small amount being associated with the pore waters. Estimated diffusive fluxes of reactive mercury ranged from 1.3 to 103 ng m(-2) d(-1). Despite the above ground biomass values being comparatively higher than below ground biomass values, the mercury pools were much higher in the root system (0.06-0.16 mg m(-2) and 29-102 mg m(-2), respectively). The annual bioaccumulation of mercury in above ground tissues was estimated in 0.11 mg m(-2) y(-1), while in below ground biomass the values were higher (7 2mg m(-2) y(-1)). The turnover rates of H. portulacoides biomass suggest higher mercury mobility within the plant rhizosphere. Taking into account the pools of mercury in above ground biomass, the export of mercury by macro-detritus following the "outwelling hypothesis" is not significant for the mercury balance in the studied ecosystem. The mercury accumulated in the below ground part of the plant is quite mobile, being able to return to the sediment pool throughout the mineralisation process.

Changes in levels of essential elements in suckling rats exposed to zinc and mercury

The effect of mercury and its interaction with zinc on the content of essential metals in tissues from neonate rats was investigated. Three-day-old Wistar rats were treated with saline or 27 mg kg(-1)d(-1) ZnCl2 (s.c.) for five consecutive days. From the 8th to the 12th day of life, the rats received one daily dose of saline or 5.0 mg kg(-1) HgCl2 (s.c). Twenty-four hours after the last injection liver, kidneys and blood were collected for metal quantification. The HgCl(2) exposure induced alterations on metal levels, such as increase of Fe, Hg and Zn in liver, decrease of Fe and Mg and increase of Cu and Hg contents in kidneys. The Hg exposure also increased Hg levels in the blood. The treatment with ZnCl2, administered previously to HgCl2, partially prevented the increase of Fe in the liver, and not only prevented the decrease of renal Mg but also increased it to levels higher than those found in control group. The Zn-Hg rats also presented higher renal Cu levels, and showed partially lower blood and hepatic Hg levels and higher renal Hg levels. The pre-administration of Zn caused no severe alterations in levels of essential metals (Cu, Fe, Mg and Mn). In short, Zn appears to be an alternative treatment of Hg poisoning in young animals in comparison to chelating drugs since these have low metal selectivity.

Erythrocytic nuclear abnormalities in wild and caged fish (Liza aurata) along an environmental mercury contamination gradient

Laranjo basin (Aveiro, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, presenting a well-described mercury gradient. This study aims the assessment of mercury genotoxicity in this area by measuring erythrocytic nuclear abnormalities (ENA) frequency in the mullet Liza aurata, and its relation with total mercury concentration (Hg(t)) in blood. Wild fish were seasonally analysed, and, complementarily, fish were caged for 3 days at three locations differing on their distances to the mercury source. The results from Laranjo were compared with those from a reference area (S. Jacinto). Wild fish from Laranjo showed elevated ENA frequency in summer and autumn in concomitance with increased blood Hg(t). Surprisingly, no ENA induction was found in winter, despite the highest blood Hg(t), which may be explained by haematological dynamics alterations, as supported by a decreased immature erythrocytes frequency. Caged fish displayed ENA induction only at the closest site to the contamination source, also showing a correlation with blood Hg(t).

Pattern and pathways for mercury lifespan bioaccumulation in Carcinus maenas

Carcinus maenas is an important and exploited natural resource in temperate estuaries, being consumed by local populations and also used as fish bait. Through bioaccumulation and bioamplification processes occurring in polluted estuarine ecosystems, this species may directly or indirectly represent a major pathway for Human contamination. No information is available on the overall lifespan bioaccumulation pattern of mercury for this species, which would be an invaluable tool for assessing the risks associated with C. maenas harvest in contaminated areas. Taking that in mind, the main objectives of this work were to clarify the lifespan bioaccumulation pattern of mercury for this species. A consistent lifespan accumulation pattern was found for this species, both for total and organic mercury, and coherent differences were found between genders, suggesting different physiological responses to contamination. From our results two scenarios emerge: (a) for low mercury contamination areas where the diet is the major pathway for metal uptake, with higher levels in muscle and hepatopancreas (twice as high as in gills) and higher organic mercury fractions (as high as 80-90% in muscle), crabs bioaccumulate with age and (b) on high contaminated areas, environmental exposure is predominant, with higher levels found in gills (reaching 0.8 mg kg(-1)), lower organic fractions and no mercury increment with age. Detoxification strategies, dietary differences and species mobility may account for these two accumulation patterns.

Antioxidant and biotransformation responses in Liza aurata under environmental mercury exposure - relationship with mercury accumulation and implications for public health

This study was carried out in the Laranjo basin (Ria de Aveiro, Portugal), an area impacted by mercury discharges. Liza aurata oxidative stress and biotransformation responses were assessed in the liver and related to total mercury (Hgt) concentrations. A seasonal fish survey revealed a sporadic increase in total glutathione (GSHt) and elevated muscle Hgt levels, although Hg levels did not exceed the EU regulatory limit. As a complement study, fish were caged for three days both close to the bottom and on the water surface at three locations, and displayed higher Hgt levels accompanied by increased GSHt content and catalase activity as well as EROD activity inhibition. The bottom group displayed higher hepatic Hgt and GSHt contents compared with the surface group. Globally, both wild and caged fish revealed that the liver accumulates higher Hgt concentrations than muscle and, thus, better reflects environmental contamination levels. The absence of peroxidative damage in the liver can be attributed to effective detoxification and antioxidant defense.

[Interobserver correlation in the interpretation of 99mTc-sestamibi SPECT in reperfused acute myocardial infarction]

INTRODUCTION AND OBJECTIVES

The correct interpretation of myocardial perfusion single photon emission computed tomography (SPECT) requires knowledge of the technique reproducibility. The objective was analyze the interobserver correlation of different experience in the interpretation of myocardial perfusion SPECT in patients following acute myocardial infarction (AMI) in order to improve the quality of our site.

METHODS

Sixty cases (56 +/- 11 years, 87 % men) with transmural AMI who had recently undergone successful thrombolysis were included. Resting perfusion with (99m)Tc-sestamibi was performed at one week post-AMI.

ANALYSIS

Semiquantitative interpretation using 17 segment-model by 2 independent specialists and 5 observers, was performed blindly. Left ventricular ejection fraction (LVEF) was measured with isotopic ventriculography one month after AMI, with a mean of 38 %.

RESULTS

Using independent and then agreed on perfusion analysis, average involved segments/patient was 9.3 +/- 4 and the sum of severity 25 +/- 13. Readings of other observers ranged from 7 +/- 3.7 to 9.4 +/- 3.9 and 16.7 +/- 9.7 to 24.6 +/- 13, respectively, consistent with the reading of the specialists of between 0.779-0.871 (kappa: 0.565-0.741). There was no significant difference when the number of segments were analyzed in 40 % of the cases and for intensity in 60 % of them in more experienced observers. Correlation with consensus reading for the number of segments ranged from 0.84 to 0.94 and for severity from 0.79 to 0.89. Identification of culprit arteries was acceptable, with r values between 0.612 and 0.683 and kappas between 0.629 and 0.656. Correlation of the number of involved segments and severity with LVEF performed one month after AMI was 0.73 and 0.74, respectively.

CONCLUSIONS

There was good correlation in the interpretation of myocardial perfusion SPECT, with a significantly better fit in more experienced observers. This academic exercise was also helpful in improving our residents' skills in cardiology.

Long-term effects of mercury in a salt marsh: hysteresis in the distribution of vegetation following recovery from contamination

During four decades, the Ria de Aveiro was subjected to the loading of mercury from a chlor-alkali industry, resulting in the deposition of several tons of mercury in the sediments. The present study evaluates the impact of this disturbance and the recovery processes, temporally and spatially, by means of examining the richness of the species of salt marsh plants and mercury concentrations in sediments over the last fifty years. The temporal assessment showed that the mercury loading induced a shift in the species composition of the salt marsh from a non-disturbed salt marsh with higher species richness to an alternative state dominated by Phragmites australis. The horizontal assessment, through a mercury gradient, presents the same trend, indicating that P. australis is the species most tolerant to higher mercury concentrations, comparative to Halimione portulacoides, Arthrocnemum fruticosum, Triglochin maritima, Juncus maritimus and Scirpus maritimus. After the reduction of mercury discharges in 1994, the salt marsh shows a slowly return path recovery response. The hysteresis in the response results in the temporal gap between the reduction in mercury concentrations in the sediment and the salt marsh species richness response, comparatively to the existing diversity in the local reference marsh.

Effects of HgCl2 on porphobilinogen-synthase (E.C. 4.2.1.24) activity and on mercury levels in rats exposed during different precocious periods of postnatal life

Porphobilinogen-synthase (PBG-synthase) is an enzyme extensively used as a bioindicator of metals and other oxidizing agents. The objective of this study was to verify the effects of HgCl(2) (5mg/kg/day, s.c.), a metal that mainly affects the nervous and renal systems, on kidney, liver and brain from rats exposed during one of the phases considered critical for development. Mercury decreased PBG-synthase activity from liver, kidney and brain and altered corporal, renal and cerebral weights. The kidney was the most sensitive tissue. It accumulated a large amount of metal and PBG-synthase activity was decreased up to 50%. The second period seemed to be the most sensitive, because in this phase the rats presented alterations in body, brain and kidney weights, and there was also an expressive inhibition in hepatic and renal PBG-synthase activities. In general, large quantities of metal accumulated in the tissues are in agreement with the inhibition verified in these tissues.

Effectiveness of ZnCl2 in protecting against nephrotoxicity induced by HgCl2 in newborn rats

This work investigated the preventive effects of ZnCl(2) on renal and hepatic alterations induced by HgCl(2) in young rats. Wistar rats of 3 days old were treated (s.c.) on consecutive days with saline or ZnCl(2) 27 mg/kg/day from the 3rd to the 7th and with saline or HgCl(2) 5.0mg/kg/day from the 8th to the 12th day of life. Pups were sacrificed 24h after the last dose and samples were collected. The creatinine and urea dosages, used as renal parameters, presented increases of 35% and 500%, respectively. The alanine aminotransferase and lactic dehydrogenase activities, used as hepatic parameters, presented a decrease (40%) and no alteration, respectively, by mercury exposure. The glycemia was diminished and the hepatic glycogen was not modified by mercury. All the mercury effects were prevented by zinc. These results suggest that mercury intoxication of young rats alters the renal function but does not modify the hepatic parameters, and previous exposure to zinc is able to avoid the renal damage.

Mercury in urban soils: a comparison of local spatial variability in six European cities

The objective of this study was to quantify and assess for the first time the variability of total mercury in urban soils at a European level, using a systematic sampling strategy and a common methodology. We report results from a comparison between soil samples from Aveiro (Portugal), Glasgow (Scotland), Ljubljana (Slovenia), Sevilla (Spain), Torino (Italy) and Uppsala (Sweden). At least 25 sampling points (in about 4-5 ha) from a park in each city were sampled at two depths (0-10 and 10-20 cm). Total mercury was determined by pyrolysis atomic absorption spectrometry with gold amalgamation. The quality of results was monitored using certified reference materials (BCR 142R and BCR 141R). Measured total mercury contents varied from 0.015 to 6.3 mg kg(-1). The lowest median values were found in Aveiro, for both surface (0-10 cm) and sub-surface (10-20 cm) samples (0.055 and 0.054 mg kg(-1), respectively). The highest median mercury contents in soil samples were found in samples from Glasgow (1.2 and 1.3 mg kg(-1), for surface and sub-surface samples, respectively). High variability of mercury concentrations was observed, both within each park and between cities. This variability reflecting contributions from natural background, previous anthropogenic activities and differences in the ages of cities and land use, local environmental conditions as well as the influence of their location within the urban area. Short-range variability of mercury concentrations was found to be up to an order of magnitude over the distance of only a few 10 m.

Can Nassarius reticulatus be used as a bioindicator for Hg contamination? Results from a longitudinal study of the Portuguese coastline

The focus of this work is to explore the use of the netted whelk, Nassarius reticulatus (L.), as an indicator of mercury (Hg) contamination, by assessing the concentration of Hg in the sediments and in the whelk along the entire Portuguese coast. Total Hg concentrations ranged from below the detection limit (0.01 ng absolute mercury) up to 0.87 mg kg(-1) dry weight (dwt) in sediments and between 0.06 and 1.02 mg kg(-1) (dwt) for organisms, with no significant differences between males and females. Although organic mercury was not detected in the sediments, it represented, on average, 52% of the total Hg in the whelk tissues, and as high as 88% in some cases, suggesting mercury accumulation from dietary intake. Significant negative correlations were found between the total Hg concentrations in the sediments and the log(10) of Hg concentrations in whelk tissues males (r=-0.64; P<0.01) and females (r=-0.52; P<0.01) indicating that the species is a poor indicator of Hg contamination. Nevertheless, since the highest concentrations of organic mercury in the whelk tissues were found in the least contaminated areas, this species must be highly relevant in the trophic web, namely on the possible biomagnification of mercury. The high dietary mercury accumulation from feeding on carrion and the low bioavailability of mercury to whelks in estuarine sediments may be the basis of the mercury accumulation pattern in N. reticulatus.