Effects of point-source PCB contamination on breeding performance and post-fledging survival in the dipper Cinclus cinclus

Despite widespread information on the incidence and biochemical effects of polychlorinated biphenyls (PCBs) in birds, field studies of effects on population processes are still scarce. This is particularly so in passerines. We therefore assessed breeding performance and post-fledging survival in dippers, Cinclus cinclus, breeding along the Afon Mule, a Welsh river where previous work indicated locally elevated PCB concentrations. We hypothesised that marked toxicological effects, including endocrine disruption, would be detectable as altered clutch-size, hatching success, nest success, brood-size, post-fledging survival or recruitment to the breeding population. Congener-specific analysis of PCBs in failed and deserted dipper eggs during 1990-93 revealed that geometric mean concentrations were four to 20 times higher along the Mule than elsewhere in Wales, UK. PCB signatures also varied highly significantly from other locations, with congeners 138, 153 and 180 dominant at the contaminated site, but 118 or 170 more frequent in eggs elsewhere. Subsequent analysis of surface runoff confirmed a small breaker's yard as a point source. Neither laying dates, clutch-sizes, brood-sizes, nest failure nor hatching failure along the contaminated Mule (n=46 breeding attempts and 218 eggs) differed significantly from dippers along adjacent reference rivers (n=82 breeding attempts and 315 eggs) or Welsh rivers as a whole (n=332 breeding attempts and 1534 eggs). Subsequent recaptures of breeding dippers ringed initially as nestlings were nearly identical between the Mule (7.7% of 182 nestlings), the reference set (7.5% of 323 nestlings) and all other Welsh rivers (7.3% of 2821 nestlings). These data illustrate the value of congener-specific analysis of bird's eggs in indicating local PCB sources. The data show also that PCBs can occur in dipper eggs at total concentrations of 0.49 (geometric mean)-1.29 (upper quartile) microg g(-1) wet mass without effects on breeding performance and survival. These values are below those at which biochemical or reproductive effects on other passerines have been detected, but above current concentrations in any other population of European dippers for which PCB data are available. Population effects by PCBs on European dippers are therefore unlikely. Survivors from locally contaminated sites like that in our study might allow field assessments of second-generation effects on breeding performance in wild birds that have developed under PCB exposure.     

Organochlorine contamination in the Great Crested Grebe (Podiceps cristatus): effects on eggshell thickness and egg steroid levels

Eggs of the Great Crested Grebe (Podiceps cristatus) were collected from a breeding area on Lake Maggiore (Northern Italy) from 2001 to 2005 in the vicinity of a p,p'-DDT manufacturer, whose production was stopped in 1996. DDT homologue and PCB congener levels were determined and compared to levels in eggs collected from other breeding areas on Lake Maggiore and in a presumably less contaminated area on Lake Garda. Although Lake Garda eggs on average possessed a lower level of p,p'-DDE than Lake Maggiore eggs, they had significantly higher levels of PCBs and could not be used as a reference population for the measurement of eggshell thickness. Nevertheless, a negative linear relationship was found between p,p'-DDE concentration and eggshell thickness for eggs collected from both lakes, indicating a possible causal relationship. Testosterone and 17beta-estradiol concentrations were also determined for eggs collected from both lakes in 2004. Average concentrations of both hormones were the lowest in eggs from Lake Maggiore; however, the very high variability within broods did not result in any significant difference between the lakes.     

Effects of point-source PCB contamination on breeding performance and post-fledging survival in the dipper Cinclus cinclus

Despite widespread information on the incidence and biochemical effects of polychlorinated biphenyls (PCBs) in birds, field studies of effects on population processes are still scarce. This is particularly so in passerines. We therefore assessed breeding performance and post-fledging survival in dippers, Cinclus cinclus, breeding along the Afon Mule, a Welsh river where previous work indicated locally elevated PCB concentrations. We hypothesised that marked toxicological effects, including endocrine disruption, would be detectable as altered clutch-size, hatching success, nest success, brood-size, post-fledging survival or recruitment to the breeding population. Congener-specific analysis of PCBs in failed and deserted dipper eggs during 1990–93 revealed that geometric mean concentrations were four to 20 times higher along the Mule than elsewhere in Wales, UK. PCB signatures also varied highly significantly from other locations, with congeners 138, 153 and 180 dominant at the contaminated site, but 118 or 170 more frequent in eggs elsewhere. Subsequent analysis of surface runoff confirmed a small breaker's yard as a point source. Neither laying dates, clutch-sizes, brood-sizes, nest failure nor hatching failure along the contaminated Mule (n=46 breeding attempts and 218 eggs) differed significantly from dippers along adjacent reference rivers (n=82 breeding attempts and 315 eggs) or Welsh rivers as a whole (n=332 breeding attempts and 1534 eggs). Subsequent recaptures of breeding dippers ringed initially as nestlings were nearly identical between the Mule (7.7% of 182 nestlings), the reference set (7.5% of 323 nestlings) and all other Welsh rivers (7.3% of 2821 nestlings). These data illustrate the value of congener-specific analysis of bird's eggs in indicating local PCB sources. The data show also that PCBs can occur in dipper eggs at total concentrations of 0.49 (geometric mean)–1.29 (upper quartile) μg g⁻¹ wet mass without effects on breeding performance and survival. These values are below those at which biochemical or reproductive effects on other passerines have been detected, but above current concentrations in any other population of European dippers for which PCB data are available. Population effects by PCBs on European dippers are therefore unlikely. Survivors from locally contaminated sites like that in our study might allow field assessments of second-generation effects on breeding performance in wild birds that have developed under PCB exposure.     

Uptake of polycyclic aromatic hydrocarbons (PAHs) in salt marsh plants Spartina alterniflora grown in contaminated sediments

Polycyclic aromatic hydrocarbon (PAH) concentrations were measured in Spartina alterniflora plants grown in pots of contaminated sediment, plants grown in native sediment at a marsh contaminated with up to 900 microg/g total PAHs, and from plants grown in uncontaminated control sediment. The roots and leaves of the plants were separated, cleaned, and analyzed for PAHs. PAH compounds were detected at up to 43 microg/g dry weight in the root tissue of plants grown in pots of contaminated soil. PAH compounds were detected at up to 0.2 microg/g in the leaves of plants grown in pots of contaminated soil. Concentrations less than 0.004 microg/g were detected in the leaves of plants grown at a reference site. Root concentration factor (RCF) values ranged from 0.009 to 0.97 in the potted plants, and from 0.004 to 0.31 at the contaminated marsh site. Stem concentration factor (SCF) values ranged from 0.00004 to 0.03 in the potted plants and 0.0002 to 0.04 at the contaminated marsh. No correlation was found between the RCF value and PAH compound or chemical properties such as logKOW. SCF values were higher for the lighter PAHs in the potted plants, but not in the plants collected from the contaminated marsh. PAH concentrations in the roots of the potted plants are strongly correlated with soil concentrations, but there is less correlation for the roots grown in natural sediments. Additional plants were grown directly in PAH-contaminated water and analyzed for alkylated PAH homologs. No difference was found in leaf PAH concentrations between plants grown in contaminated water and control plants.     

The occurrence of xenoestrogens in the Elbe river and the North Sea

The xenoestrogens Bisphenol A (BPA), p-alkylphenols and p-alkylphenol ethoxylates were determined in water samples of the North Sea, the Elbe river, and its tributaries Schwarze Elster, Mulde, Saale and the Weisse Elster. The sampling sites of the Elbe river reached from Schmilka at the German-Czech border to Cuxhaven at the estuary. Samples of the North Sea were taken in the German Bight. Additionally, freshly deposed sediments of the River Elbe and its tributaries were analyzed. Partitioning coefficients of these compounds for the distribution between suspended particulate matter (SPM) and the aqueous phase were calculated for samples of the River Elbe at sampling site Geesthacht. The analytical procedure consisted of liquid-liquid extractions of the acidified water samples using dichloromethane. Sediments and SPM samples were extracted by Accelerated Solvent Extraction with n-hexane/acetone. Following a clean-up by HPLC, the analytes were derivatized with heptafluorobutyric acid anhydride and quantified using GC-MSD. The concentration ranges of the compounds analyzed in water samples of the Elbe river were as follows (in ng l(-1)): BPA 9-776, alkylphenols 10-221 and alkylphenol ethoxylates 18-302. In sediment samples the concentrations were (in microg kg(-1) dry mass): BPA 66-343, alkylphenols 17-1378 and alkylphenol ethoxylates 30-1797. In samples of the North Sea the concentrations were generally about 1 order of magnitude lower. As shown by the concentration profiles following the River Elbe into the North Sea, the Elbe river must be considered as a major pollution source for the North Sea concerning the compounds analyzed. The SPM/water-partitioning coefficients calculated (mean values) amounted to: BPA 4.50, alkylphenols 5.52-5.58 and alkylphenol ethoxylates 5.60-6.38. A comparison of the results with data from other surface waters showed that concentrations of these xenoestrogens in the River Elbe and its tributaries were relatively low. The evaluation of the data based on the lowest observable effect concentration (LOEC) for alkylphenols (endpoint: vitellogenin synthesis in male trout) indicated that the concentrations were well below the effectivity threshold.     

Organochlorine contaminants in eggs of Common Terns from the Canadian Great Lakes, 1981

To determine if contaminant levels in Common Terns had changed over the last decade, we collected and analyzed eggs from four nesting colonies on the three lower Great Lakes during 1981. DDE and PCBs were detected in every egg from the four colonies. Dieldrin, mirex and trans-nonachlor were detected in more than 45% of the eggs. Seven other organochlorine contaminants (DDD, DDT, hexachlorobenzene, oxychlordane, cis-chlordane, cis-nonachlor and toxaphene) were detected in less than 25% of the eggs. Eggs from the Lake Ontario colony were generally the most heavily contaminated. Comparisons of DDE and PCB data with earlier studies of Common Terns indicated that contaminant levels in eggs from the four sampled colonies, or nearby sites, have decreased by up to 80-90% from 1969-1973 to 1981. Interspecies comparisons showed that Common Tern eggs have lower organochlorine residue levels than eggs of Caspian Terns or Herring Gulls. Dietary variation and migratory status are possible explanations for the differences in residue levels among species. Eggshell thickness, log-PCBs, and log-DDE were not significantly intercorrelated. Elevated contaminant levels in the early 1970s might be at least partly responsible for the decline of the Great Lakes Common Tern population over the past decade. Stabilization of population numbers during the early 1980s suggests that organochlorine pollution levels have been reduced to a point where they are no longer an important factor in the population dynamics of this species on the Great Lakes.     

PCBs, dioxins and furans in Hooded Merganser (Lophodytes cucullatus), Common Merganser (Mergus merganser) and mink (Mustela vison) collected along the St. Maurice River near La Tuque, Quebec

A pulp and paper mill located in La Tuque on the St.Maurice River, Quebec, and using the kraft bleaching process was historically the largest pulp and paper industry point source of chlorinated dibenzo-p-dioxins and dibenzofurans in Quebec. A study was undertaken to document the bioaccumulation of PCBs, dioxins and furans in piscivorous birds and mammals in this area. Hooded and Common Merganser eggs were collected in nest boxes along the St.Maurice River and Common Merganser fledglings were collected at two sites on the river. Wild minks were trapped along the St.Maurice River and in a control area upstream. Analysis of pooled merganser eggs showed contamination with dioxins, furans and PCBs. Liver samples of fledglings were contaminated with 2,3,7,8-tetrachlorodibenzofuran at the downstream site. Analysis of mink livers showed a significant higher contamination with dioxins and furans in some downstream samples compared with the upstream samples.     

MTBE and aromatic hydrocarbons in North Carolina stormwater runoff

A total of 249 stormwater samples were collected from 46 different sampling locations in North Carolina over an approximate 1-year period and analyzed to identify land use types where fuel oxygenates and aromatic hydrocarbons may be present in higher concentrations and at greater frequency. Samples were analyzed by gas chromatography-mass spectrometry in ion selective mode to achieve a quantitation limit of 0.05 microg/l. m-,p-Xylene and toluene were detected in over half of all samples analyzed, followed by MTBE: o-xylene: 1,3,5-trimethylbenzene: ethylbenzene; and 1,2,4-trimethylbenzene. Benzene, DIPE, TAME and 1,2,3-trimethylbenzene were detected in < 10% of the samples analyzed. Median contaminant concentrations (when detected) varied from 0.07 microg/l for ethylbenzene to 0.11 microg/l for toluene. All of the locations with significantly higher contaminant concentrations were associated with direct runoff from a gas station or discharge of contaminated groundwater from a former leaking underground storage tank. For all of the aromatic hydrocarbons, the maximum observed contaminant concentrations were over an order of magnitude lower than current drinking water standards.     

Reproductive success and chlorinated hydrocarbon contamination of resident great blue herons (Ardea herodias) from coastal British Columbia,Canada, 1977 to 2000

Over the period 1977-2000, eggs of Pacific great blue heron (Ardea herodias fannini) were collected from 23 colonies along the southern coast of British Columbia, Canada, and analyzed for persistent organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Concentrations of OC pesticides in eggs declined sharply in the late 1970s, after which there were minimal changes. The sums of PCB congeners were not reduced appreciably during the 1980s and 1990s, but Aroclor 1260 concentrations suggested a sharp decline in PCB contamination of eggs in the late 1970s, similar to that shown for OC pesticides. Eggs collected along or near the Fraser River delta showed higher levels of most pesticides compared to other monitored colonies. Although the delta lands support a long-standing agricultural economy, the primary factors influencing OC levels in the delta colonies were thought to be driven by estuarine processes. We suggest two possible influencing factors were: 1) a greater rate of bioaccumulation in the estuary due to the deposition of particulates collected over a vast area encompassed by the Fraser River watershed; or 2) a higher rate of biomagnification in the estuary due to species differences at lower trophic levels of the heron food chain. Eggs from urban colonies contained higher levels of PCBs. The congener pattern was not clearly different from that observed in less contaminated eggs from rural and pulp mill-influenced colonies, except that colonies in Vancouver had greater proportions of PCB-66, suggesting a local source of Aroclor 1242. Productivity in the coastal heron colonies was highly variable over the period of study, with 71% of recorded colony-wide reproductive failures occurring in colonies near pulp mills. However, the predominant factors influencing reproductive success were probably disturbance by humans and bald eagles, combined with loss and degradation of nesting habitat, and not sublethal toxicity.     

Metal bioaccumulation and metallothionein concentrations in larvae of Crassostrea gigas

Larval stages of bivalve molluscs are highly sensitive to pollutants. Oysters from a hatchery from Normandy (English Channel) were induced to spawn, and fertilized eggs were exposed to copper or cadmium for 24 h. Metal accumulation (from 0.125 to 5 microg Cu L(-1) and from 25 to 200 microg Cd L(-1)) and MT concentrations were measured in larvae. Compared to controls, larvae accumulated copper and cadmium with an increase in MT concentrations particularly with cadmium (i.e. 130.96 ng Cu (mg protein)(-1) and 12.69 microg MT (mg protein)(-1) at 1 microg Cu L(-1) versus 23.19 ng Cu (mg protein)(-1) and 8.92 microg MT (mg protein)(-1) in control larvae; 334.3 ng Cd (mg protein)(-1) and 11.70 microg MT (mg protein)(-1) at 200 microg Cd L(-1) versus 0.87 ng Cd (mg protein)(-1) and 4.60 microg MT (mg protein)(-1) in control larvae). Larvae were also obtained from oysters of a clean area (Arcachon Bay) and a polluted zone (Bidassoa estuary) and exposed to copper in the laboratory, their MT concentration was measured as well as biomarkers of oxidative stress. Biomarker responses and sensitivity to copper for the larvae from Arcachon oysters were higher than for those from Bidassoa.     

Negative effects of humic acid addition on phytoremediation of pyrene-contaminated sediments by mangrove seedlings

Vegetated (with Kandelia candel seedlings) and non-vegetated mangrove microcosms were employed to remove pyrene from contaminated sediments, and the effects of adding 6.7% humic acid (HA) on such removal were investigated. At the end of 6-month treatment, residual pyrene concentrations in surface sediments (0-2 cm) of the contaminated microcosms reduced from an initial 5.82 to 0.63 microg g(-1) dw, and the reduction was less in HA amended microcosms with the residual pyrene concentration remained at 3.12 microg g(-1) dw. The pyrene removal percentages in microcosms with HA amendment were 29% for surface aerobic sediments and 41% for bottom (anaerobic) sediments, while the respective removal percentages in microcosms without HA amendment were 89% (surface sediments) and 53% (bottom sediments). Microcosms planted with K. candel seedlings had a significantly higher pyrene removal when compared to the non-vegetated ones, and the average removal percentages were 70.9% and 61.4%, respectively. However, when humic acid was added, no significant difference was found between vegetated and non-vegetated microcosms in pyrene removal, both had less than 40% removal, probably because plant growth in humic acid amended contaminated microcosms, in terms of total biomass, was reduced by 50%. Roots of K. candel could accumulate pyrene from contaminated microcosms, and pyrene concentrations in roots harvested from microcosms with and without humic acid addition were 6.01 and 3.46 microg g(-1) dw, respectively. These results suggest that the addition of HA to contaminated sediments decreased the mangrove microcosm's ability to remove pyrene as pyrene was more tightly bound to the organic matter and plant growth was reduced.     

Bird blood as bioindicator for mercury in the environment

Mercury concentrations were studied in blood, down and feathers of Common Gull (Larus canus L.) to investigate the suitability of bird blood as a matrix for biomonitoring of mercury in the marine environment. Chicks were collected in 1996 on the Elbe river and the Jade Bay. Like the side feathers, blood indicated site differences in mercury contamination. Correlational analyses showed that mercury concentrations in blood are significantly related to levels in side feathers (p < 0.001; Pearson), but not to those in down (p > 0.05; Pearson). Therefore, blood can be considered as a suitable matrix to indicate the current mercury burden in wild birds.     

Patterns of contamination by organochlorines and mercury in the eggs of two river passerines in Britain and Ireland with reference to individual PCB congeners

Unhatched eggs were collected in 1988 and 1990 from nests of the Eurasian Dipper Cinclus cinclus and the Grey Wagtail Motacilla cinerea in Wales, eastern Scotland and south-western Ireland. Mercury concentrations in Dipper eggs (geometric means 0.45-0.91 ppm (microg g(-1)) dry mass) were significantly lower in eastern Scotland than in either south-western Ireland or Wales, where the incidence of detectable residues increased markedly between 1988 (2% of eggs) and 1990 (69%). By contrast, DDE (geometric means 0.63-3.54 ppm in lipid), TDE (<0.01-1.80 ppm), DDT (<0.01-0.65 ppm), total PCBs (3.99-10.47 ppm), HEOD (0.39-0.61 ppm) and HCB (0.02-0.13 ppm) were all significantly higher in Scottish eggs than others. Around 33-46% of the total PCB burden in Dipper and Grey Wagtail eggs could be accounted for by six congeners (IUPAC numbers 118, 180, 101, 153, 138 and 170). Amongst these attributable PCBs, Dipper eggs from eastern Scotland were dominated by congener 153 (2,2',4,4',5,5'-hexachlorobiphenyl), whilst Welsh and Irish eggs were dominated by congener 118 (2,3',4,4',5-pentachlorobiphenyl). With the latter exception, all the individual congeners were found at significantly higher concentrations in Scottish eggs than others. Grey Wagtail eggs were dominated by congeners 118 and 101 (2,2,4,5,5'-pentachlorobiphenyl). In general, these congeners are common, widespread, and dominant components in the eggs of other wild birds for which data are available. Consistent with the low to medium levels of contaminants found in Dipper eggs, there was only slight evidence of any toxic effects. These included moderate shell thinning in relation to increasing DDE, and some evidence that contaminants had contributed to egg failure.     

Temporal variability in particle-associated pesticide exposure in a temporarily open estuary, Western Cape, South Africa

This study assesses the risk of current-use pesticides in a temporarily open estuary in South Africa by developing probabilistic risk estimates. Particle-associated pesticides (chlorpyrifos, prothiofos, cypermethrin, fenvalerate, endosulfan and p,p-DDE) and physicochemical parameters (salinity, temperature, flow, and total organic content (TOC)) were measured in the Lourens River estuary (Western Cape) twice a month over a period of two years and equilibrium partitioning theory was applied to calculate concentrations of pesticides in the water. The 90th percentile concentrations of pesticides associated to suspended particles and the calculated concentrations in water were 34.0microg kg(-1) and 0.15microg l(-1) for prothiofos, 19.6microg kg(-1) and 0.45microg l(-1) for chlorpyrifos and 18.6microg kg(-1) and 0.16microg l(-1) for endosulfan. Highest average concentrations were found around the summer season due to higher application rates and as a result of the low flow during this season. Species sensitivity distribution indicated a 1.5-2.8 times higher toxicity (hazardous concentration HC5) for marine organisms compared to freshwater organisms. The calculated concentrations in the water exceeded all threshold values suggested by international water guidelines. Chlorpyrifos and endosulfan posed the highest acute risk to the Lourens River estuary. No sufficient toxicity data and threshold values were found for prothiofos.     

Mussel watch: a review of Cu and other metals in various marine organisms in Taiwan, 1991-98

This study presents the distribution of Cu, Zn, Pb, Cd, Hg and As in various marine organisms collected along the western coast of Taiwan from 1991 to 1998, and also evaluates the time variation of Cu in oysters before (1980-85) and after (1986-98) the "green oyster" incident. The results show that relatively high geometric mean (GM) concentrations of Cu, Zn, Pb, Cd, As and Hg were generally found in Crassostrea gigas (Cu=229 microg/g, Zn=783 microg/g), Gomphina aeguialtera (Pb=30.3 microg/g), Tegillarca granosa (Cd=2.85 microg/g), Thais clavigera (As=96.9 microg/g) and Parapenaeopsis cornuta (Hg=1.35 microg/g), respectively. Especially, maximum Cu and Zn concentrations (GM=229 and 783 microg/g, respectively) in oysters (C. gigas) from different culture areas were much higher than those of the other organisms by about 1.13-458 and 2.40-63.7 times, respectively. Similarly, rock-shells (Thais clavigera) had a high capacity for accumulating Cu (GM=202 microg/g) and Zn (GM=326 microg/g) under the same physico-chemical conditions. The highest GM Cu and Zn concentrations of 1108 (range from 113 to 2806) and 1567 (range from 303 to 3593) microg/g were obtained in oysters from the Hsiangshan coastal area, one of the most important oyster culture areas in Taiwan. However, the highest GM Cd and As concentrations of 6.82 and 19.3 microg/g were found in oysters from the Machu Islands. Mean Cu concentrations in the oysters from the Erhjin Chi estuary declined from 2194+/-212 microg/g in 1986-90 to 545 microg/g (GM) in 1991-96. In the Hsiganshan area, GM Cu concentrations of 909 microg/g (1991-96) and 1351 microg/g (1997-98) in oysters were significantly higher than those of 201 microg/g (1980-85) and 682 microg/g (1986-90). The gradually increasing levels of Cu and Zn in the oysters from the Hsiangshan area have been observed year by year.     

Reduced breeding success of Cormorants (Phalacrocorax carbo sinensis) in relation to persistent organochlorine pollution of aquatic habitats in The Netherlands

Cormorants (Phalacrocorax carbo sinensis) breeding in the heavily contaminated sedimentation area of the rivers Rhine and Meuse have a severely reduced breeding success as compared to several other Dutch colonies. A detailed analysis of reproductive performance in combination with chemical analysis of eggs and food from colonies in differently contaminated aquatic habitats is presented. The differences in breeding success between colonies are caused mainly in the egg-stage of breeding. Eggshell thinning and increased embryonic mortality cause the differences in hatching success. The observed effects seem to be related to chlorinated hydrocarbons. Significant correlations are found for concentrations of DDE with eggshell thinning and for concentrations of PCBs with hatching and breeding success. The correlations between concentrations of chlorinated hydrocarbons in eggs and biological effects measured in the field are established both on colony and individual clutch level.     

Mercury bioaccumulation and risk to three waterbird foraging guilds is influenced by foraging ecology and breeding stage

We evaluated mercury (Hg) in five waterbird species representing three foraging guilds in San Francisco Bay, CA. Fish-eating birds (Forster's and Caspian terns) had the highest Hg concentrations in thier tissues, but concentrations in an invertebrate-foraging shorebird (black-necked stilt) were also elevated. Foraging habitat was important for Hg exposure as illustrated by within-guild differences, where species more associated with marshes and salt ponds had higher concentrations than those more associated with open-bay and tidal mudflats. Importantly, Hg concentrations increased with time spent in the estuary. Surf scoter concentrations tripled over six months, whereas Forster's terns showed an up to 5-fold increase between estuary arrival and breeding. Breeding waterbirds were at elevated risk of Hg-induced reproductive impairment, particularly Forster's terns, in which 48% of breeding birds were at high risk due to their Hg levels. Our results highlight the importance of habitat and exposure timing, in addition to trophic position, on waterbird Hg bioaccumulation and risk.     

Removal of pyrene from contaminated sediments by mangrove microcosms

The potential of mangrove wetland systems to remove pyrene from surface- or bottom-contaminated sediments was investigated by microcosm studies. The performance of two mangrove plant species, Kandelia candel and Bruguiera gymnorrhiza in pyrene removal was also compared. During the six-months experimental period, the growth of both species in the surface-contaminated microcosms was not significantly different from that in the bottom-contaminated ones, and was comparable to the control (without any pyrene contamination). At the end of six-months treatment, pyrene concentrations in contaminated sediments declined from an initial 3 microg g(-1) to less than 0.4 microg g(-1), indicating that pyrene was successfully removed by mangrove microcosms. Around 96.4% and 92.8% pyrene in microcosms planted with K. candel were removed from the surface- and bottom-contaminated sediments, respectively. The removal percentages were slightly lower in microcosms planted with B. gymnorrhiza. Significant accumulation of pyrene in roots was only found in microcosms having bottom-contaminated sediments, and pyrene concentrations were 3.05 microg g(-1) and 4.50 microg g(-1) in roots of K. candel and B. gymnorrhiza, respectively. These values were much higher than that in control microcosms (without pyrene contamination, root pyrene concentrations were 0.27 microg g(-1) for K. candel and 0.34 microg g(-1) for B. gymnorrhiza) and in microcosms with contaminated sediments placed at the surface layer. Nevertheless, the overall contribution of root accumulation and plant uptake to the removal of pyrene from contaminated sediments was insignificant.     

Short-term Pb accumulation by slugs sampled from clean and contaminated sites when fed artificial Pb-spiked diets

Slugs (Deroceras reticulatum and Arion subfuscus) were sampled from two distinct sites, an uncontaminated site at Dinas Powys and a Pb-contaminated, disusedmine site at Llantrisant. Batches of the slugs were exposed for ten days under laboratory conditions to an artificial diet consisting of a 5% (w/v) agar + 5% (w/v) sucrose matrix contaminated with different concentrations of Pb, as Pb (NO(3))(2). The food 'cubes' contained approximately 0, 10, 100, and 1000 microg Pb ml(-1). Tissue-Pb concentrations increased with increasing dietary-Pb concentration in both species. However, at the highest Pb exposure (1000 microg ml(-1)) the tissue-Pb concentrations in D. reticulatum and A. subfuscus sampled originally from the clean site were higher than those in their counterparts from the contaminated site, even though the Llantrisant slugs had significantly higher baseline Pb concentrations than the Dinas Powys slugs. It is suggested that these observations indicate metal tolerance phenotypically expressed as reduced accumulation in the populations with a history of Pb-exposure in their natural habitat. We discuss how biomonitoring may be affected by the way in which different slug populations deal with metals.     

Dioxins and congener-specific polychlorinated biphenyls in three avian species from the Wisconsin River,Wisconsin

Sediments from the Wisconsin River. WI. USA are contaminated with 2,3,7,8-tetrachloro-p-dioxin (TCDD) and polychlorinated biphenyls (PCBs). Wet weight concentrations of TCDD and PCBs in eggs were at background levels and highest in the piscivorous = 7 pg/g TCDD a hooded merganser (Lophodytes cucullatus; geometric m ean nd 0.92 microg/g PCBs) a nd lowest in the omnivorous wood duck (Aix sponsa) (< 1 pg/g and 0.07 microg/g); concentrations in eggs of the insectivorous tree swallow (Tachycineta bicolor) were intermediate (< 1 pg/g and 0.33 pg/g). Positive accumulation rates of TCDD (8-19 pg/day) and PCBs (0.4-0.7 microg/day) in tree swallow nestlings suggest that the Wisconsin River is the source of these contaminants for tree swallow nestlings. The lower representation of trichlorobiphenyls and tetrachorobiphenyls in hooded merganser eggs compared to wood duck or tree swallow eggs suggests that the hooded merganser or its diet has a greater ability to metabolize lower-numbered PCB congeners than wood ducks or tree swallows.