Concentrations Of Organochlorine Contaminants Research Articles

Using Plasma Vitellogenin in Loggerhead Sea Turtles to Assess Reproductive Maturation and Estrogen-Like Contaminant Exposure.

Vitellogenin (VTG), an egg yolk precursor, is abnormally produced by male and juvenile oviparous species after exposure to estrogens. Plasma VTG in loggerhead sea turtles (Caretta caretta) helped us understand their reproductive maturation and investigate it as a biomarker of contaminant exposure. The presence of VTG was screened in plasma from 404 loggerheads from the northwestern Atlantic Ocean using a freshwater turtle antibody in western blots. The concentrations of VTG were semiquantified using band intensities calibrated to results from a loggerhead antibody enzyme-linked immunoassay. The detection and concentrations of VTG were in (from highest to lowest): nesting females, in-water adult females, subadult females, smaller females, unknown sex, and males. Loggerheads from this region begin vitellogenesis at ≅77 cm straight carapace length. We classified VTG expression as abnormal in nine male or juvenile turtles. Organochlorine contaminant (OC) concentrations were measured in blood and/or fat biopsies of some turtles. One abnormal VTG female had the second highest fat polychlorinated biphenyl (PCB) and 4,4'-dichlorodiphenyldichloroethylene concentrations compared among 43 VTG-negative juveniles. The nine VTG-abnormal turtles had average blood PCB concentrations 8.5% higher, but not significantly different, than 46 VTG-negative juveniles (p = 0.453). In turtles less than 77 cm, blood PCB concentrations were significantly, but weakly, correlated with semiquantified VTG concentrations (tau = 0.1, p = 0.004). Greater blood OC concentrations were found in adult females than in males, which motivated the creation of a conceptual model of OC, VTG, and hormone concentrations across a reproductive cycle. A decision tree is also provided incorporating VTG as a sexing tool. Abnormal VTG expression cannot conclusively be linked to endocrine disruption caused by these OC concentrations. Studies should further investigate causes of abnormal VTG expression in wild sea turtles. Environ Toxicol Chem 2023;42:1309-1325. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

The combined use of organochlorine contaminant profiles and molecular genetics for stock discrimination of white whales (Delphinapterus leucas) hunted in three communities on southeast Baffin Island

Putative stock differences in white whales (Delphinapterus leucas) landed by hunters between 1992 and 1996 from the southeast Baffin Island communities of Kimmirut (KI), Iqaluit (IQ) and Pangnirtung (PA) were examined using organochlorine contaminant (OC) profiles of 124 whales, the molecular genetics of 270 whales and both types of data from 97 whales. OC concentrations were generally lower in whales hunted in PA than those hunted in KI and IQ, and many OCs were lower in KI than IQ. In canonical discriminant function (CDA) using 13 OC predictor variables (10 OC groups, mirex, octachlorostyrene and endosulfan), the first canonical function accounted for 77% of the variance and separated whales from PA with those from IQ and KI; the second canonical function separated whales from KI with those from IQ. A previous study of the molecular genetics of white whales showed that whales hunted in the three communities were significantly differentiated on the basis of haplotype and/or microsatellite allele frequencies (de March et al., 2002). When the results of two studies were combined, many whales were slightly more strongly associated with a particular source hunting community than they were in the component studies. Using a posteriori crossvalidation probabilities in an analysis with variables from both studies, 72% of white whales were correctly crossvalidated to their source hunting community; 82.5% from PA; 56.5% from IQ; and 58.8% from KI. The highest misclassification rates were KI to IQ (23.5%), IQ to KI and IQ to PA (21.7% in both cases) and the lowest rates were PA to KI (3.5%), PA to IQ (14.0%) and KI to PA (17.6%). This pattern of assignments was not significantly different from those in the genetics or contaminants studies alone. However, the crossvalidation probabilities to the most likely source communities were approximately 20% larger in the combined analysis than in the component studies. Canonical scores in the combined analysis were more strongly correlated with variables from the OC Study than with variables from the genetics study. Whales placed to PA and IQ could be identified primarily by their OC signatures, however many whales from PA also had a strong PA genetics signature. Whales from IQ were identifiable only by their OC signatures. Both a strong KI genetics and OC signature described approximately half of whales from KI. We believe that at least three stocks were sampled from the three communities. Some whales in PA were very distinct, confirming previous beliefs that a separate stock occurs in Cumberland Sound. Whales hunted in IQ and KI differed to a lesser degree, and may be from stocks subject to a gradient or from a mixture of stocks. Some whales from PA are more likely to have genotypes and OC signatures that are also found in IQ and KI than the reverse. It is possible that summering areas of the stocks that were identified in KI and IQ are not consistent from year to year or across generations. The main problems in combining results for individuals used in several studies, particularly when there are many measurements for relatively few individuals, is to find a limited number of relevant predictor variables that can be used in the combined analysis, while avoiding both overparameterisation and results blurred by meaningless variables.

Concentration dynamics of polychlorinated biphenyls and organochlorine pesticides in blood of growing Grey heron (Ardea cinerea) chicks in the wild

Organochlorine contaminants (OCs) – organochlorine pesticides (OCPs) and industrial products and byproducts – are included in different monitoring programmes and surveys, involving various animal species. Fish-eating birds are suitable indicator species for OCs. Adult birds may be difficult to capture, but chicks can be sampled more easily. Blood of birds is a potentially suitable non-destructive matrix for analysis, as OC levels in blood reflect their concentrations in the body. The study was aimed at investigating how age of fast-growing Grey heron (Ardea cinerea) chicks affects contaminant levels in their blood and thus how important is sampling at exact age for biomonitoring purposes. In 1999 on Lake Engure in Latvia whole blood samples of heron chicks were collected at three different time points, with seven and nine days in between the first and second and second and third sampling points, respectively. Twenty-two chicks were sampled at all three times. In total, 102 samples were analysed for 19 polychlorinated biphenyl (PCB) congeners, DDT metabolites – DDE and DDD, hexachlorobenzene (HCB), α-, β-, γ-hexachlorocyclohexane (HCH), and trans-nonachlor. Total PCB concentrations averaged around 2000 ng/g dry extracted matter (EM). DDE was the dominant individual contaminant (ca. 800 ng/g EM), followed by CB-153, -138, and −118. Most of the other analysed OCs were below 100 ng/g EM. No significant (p > 0.05) differences in OC concentrations were found between the three sampling occasions, except for trans-nonachlor. This means that blood can safely be sampled for biomonitoring purposes during the 17 days’ time window. The analysed legacy contaminants may serve as model substances for other persistent organic pollutants.

Organochlorine contaminant concentrations in blubber of young Steller sea lion (Eumetopias jubatus) are influenced by region, age, sex, and lipid stores

Contaminant exposure is particularly important for species and populations of conservation concern, such as the Steller sea lion (Eumetopias jubatus). We used blubber samples (n = 120) to determine organochlorine concentrations, including polychlorinated biphenyls (PCBs) and dichloro-diphenyl-trichloroethane (DDTs), and blood samples (n = 107) to estimate total body lipids based on the hydrogen isotope dilution method. We assessed the influence of age, sex, condition, and geographic area on contaminant concentrations in blubber and contaminant body load. The concentration of ΣPCBs was highest in pups (<6 months) from the Aleutian Islands, and the concentrations in males were higher than females in all regions. The ΣPCBs and ΣDDTs concentrations and loads decreased with increasing mass in pups, however, there were no regional or sex differences in contaminant load. Within each of the five age classes, the concentrations of ΣPCBs and ΣDDTs decreased with increasing mass, but overall these OCs increased with age. Further, accounting for the lipid content, a potential proxy for energy balance, in the animal load reduced or removed the regional and sex effects present in age models for contaminants. We propose, that adjusting OCs concentration by the lipid content of the blubber sample alone may not fully account for the variability in OC concentrations associated with differences in condition or energy states between young Steller sea lions.

Trophic transfer of persistent organic pollutants through a pelagic food web: The case of Lake Como (Northern Italy)

Despite DDT and PCB having been banned for about 40 years, they are still detectable in the environment. In the present research we specifically investigated the trophic transfer of these organochlorine contaminants (OC) through a pelagic food web of a deep lake in Northern Italy (Lake Como) over time. Zooplankton and fish were sampled each season of a year and OC concentrations and the carbon and nitrogen isotopic ratios were measured. By using stable isotopes, the direct trophic relationship between pelagic zooplankton and zooplanktivorous fish was confirmed for Alosa agone only in summer. Based on this result, the biomagnification factor normalized on the trophic level (BMFTL) for organic contaminants was calculated. BMFTL values were within the range 0.9–1.9 for DDT isomers and 1.6–4.9 for some PCB congeners (PCB 95, PCB 101, PCB 149, PCB 153, PCB 138 - present both in zooplankton and in fish and representing >60% of the PCB contamination), confirming the biomagnification of these compounds in one of the two zooplanktivorous fish species of the lake.

Organochlorine Contaminants, Immunocompetence and Vitellogenin in Herring Gulls (Larus argentatus) and Great Black-Backed Gulls (Larus marinus) Nesting on Lake Ontario in 2001–2002

Abstract. In 2001–2002, Great Black-backed Gull (Larus marinus) eggs from Lake Ontario had significantly higher concentrations of organochlorine contaminants than Herring Gull (L. argentatus) eggs. This study investigated whether higher contaminants in Great Black-backed Gulls affected immunocompetence, packed cell volume (PCV) and body condition in chicks, endocrine disruption and body condition in adults, and reproductive success. Variables were compared between species at two Lake Ontario sites (one in Ontario, Canada, and one in New York, USA), and with a control site in the Bay of Fundy, Canada. For Herring Gull chicks, body condition and total antibody titers to sheep red blood cells were greater at one contaminated site; PCV, phytohemagglutinin-P stimulation and reproductive output did not differ among sites. For Great Black-backed Gull chicks, PCV was significantly lower at one contaminated site; there were no other significant differences among sites. Between species, Herring Gull chicks had sign...

Organochlorine contaminant concentrations in multiple tissues of free-ranging Steller sea lions (Eumetopias jubatus) in Alaska

The relationships of selected organochlorine (OC) contaminants between blubber, blood, feces, and milk of young, free-ranging Steller sea lions (Eumetopias jubatus) were examined. Both between and within each tissue there was considerable individual variation. In spite of the variation, similar patterns were observed across the tissues for most of the selected PCB congeners. In all four tissues, the major PCB congeners were PCB101, PCB118, PCB138, and PCB153. The most prominent congener, both as a weight (ng/g lipid) and as a percentage of summed PCBs (∑PCBs), was PCB 153. Comparisons between paired tissues showed that ∑DDTs in blubber samples were related to concentrations in blood, feces, and milk. The ∑PCBs in blubber were related to concentrations in milk and fecal samples, though the relationship with feces was weak. Our findings show milk samples, in particular, are useful for assessing OCs in young sea lions. Blubber concentrations of PCB101, PCB118, and PCB138 were an order of magnitude higher than those in milk, supporting the biomagnification of these PCB congeners in SSL tissues. The findings indicate alternative tissues may be used as indicators of relative contaminant exposure in lieu of surgical blubber biopsy.

Stable isotopes of carbon and nitrogen in the study of organochlorine contaminants in albatrosses and petrels

Carbon and nitrogen stable isotopes in albatrosses and petrels collected off southern Brazil were compared with concentrations of organochlorine contaminants (OCs). δ13C and δ15N values, as well as OCs concentrations, exhibited a high degree of variability among individuals and overlap among species. δ13C values reflected latitudinal differences among species, with lower values found in Wandering and Tristan Albatrosses and higher values found in Black-browed and Atlantic Yellow-nosed Albatrosses and White-chinned Petrels. Some relationships were found between OCs and stable isotopes, but in general a partial ‘uncoupling’ was observed between OCs concentrations and stable isotopes ratios (especially for δ15N). δ13C and δ15N values in Procellariiformes tissues during the non-breeding season appear to be a better indicator of foraging habitats than of trophic relationships, which may partially explain the high degree of variability between concentrations of OCs and stable isotopes ratios in birds with a diversified diet and wide foraging range.

Population surveys in Greenland 1993–2009: Temporal trend of PCBs and pesticides in the general Inuit population by age and urbanisation

The purpose of the study was to analyse temporal trends (1993–2009) of the concentrations of organochlorine contaminants (14 congeners of polychlorinated biphenyls (PCB) and 11 pesticides) in the blood of Greenland Inuit according to age and urbanisation. Statistical determinants for the contaminant concentrations included (for PCB congener 153) age (Δr2=0.35), marine diet (Δr2=0.10), smoking (Δr2=0.02), and sex (Δr2=0.01) with comparable results for other organochlorine contaminants. After adjustment for age, diet, smoking, and sex a significant decreasing trend was present for all contaminants ranging from 41% for mirex to 56% for hexachlorobenzene. The temporal trend was most pronounced among participants below the age of 65years. The decrease started later in villages than in towns. The decrease was present in all age groups and in the capital, other towns, and villages. The decrease is probably due to a combination of reduced concentrations of the contaminants in the wildlife and a slight temporal reduction in the consumption of marine mammals. The significant downwards trend of legacy POPs shows that the legislation works but it must be kept in mind that according to the cumulated scientific evidence there are a multitude of non-regulated persistent organic contaminants in the diet as well as high levels of methylmercury.

Improved reproductive success in otters (Lutra lutra), grey seals (Halichoerus grypus) and sea eagles (Haliaeetus albicilla) from Sweden in relation to concentrations of organochlorine contaminants

We studied indices of reproductive outcome in three aquatic species in relation to organochlorine concentrations during four decades. In female otters, the frequency of signs of reproduction increased after 1990. In grey seals, pregnancy rate increased 1990–2010 and uterine obstructions ceased after 1993. The frequency of uterine tumours was highest 1980–2000. The number of sea eagle nestlings per checked nest increased 1985–2000, while the frequency of desiccated eggs decreased. Organochlorine concentrations decreased at annual rates between 3.5 and 10.2%. The estimated mean concentration (mg/kg lw) for total-PCB decreased from 70 to 8 (otters), from 110 to 15 (seals) and from 955 to 275 (eagles). The corresponding concentrations for ΣDDT decreased from 3.4 to 0.2 (otters), from 192 to 2.8 (seals) and from 865 to 65 (eagles). This study adds evidence to support the hypothesis that PCBs and DDTs have had strong negative effects on the reproduction and population levels of these species.

Assessment of organochlorine pesticides in human milk and risk exposure to infants from North-East India

Despite the worldwide ban on use of persistent organochlorine pesticides, their usage continued until recently in India, for vector-borne disease eradication programs and agricultural purposes. The concentrations of organochlorine contaminants, DDT and HCH, have been determined in human breast milk from Dibrugarh and Nagaon districts of Assam state, North-East India. The results demonstrated that the mean levels of total DDT were 3210 ng/g lipid wt. and 2870 ng/g lipid wt. and total HCH were 2720 ng/g lipid wt. and 2330 ng/g lipid wt. in Nagaon and Dibrugarh respectively. There was no significant difference in the levels of investigated pollutants between the two districts. Significant differences in ADI (Average daily intake) for total DDT were found between the two districts. In addition, a positive correlation was observed between OCP levels in breast milk and age of mothers. Based on OCP levels in human breast milk, the ADI by the infants has been estimated. It has been found that high daily intake of DDTs and HCHs by the infants exceeded the TDI (Tolerable daily intake) which implied that infants of the region are potentially at high risk by these contaminants.

PCB and organochlorine pesticides in northern fulmars (Fulmarus glacialis) from a High Arctic colony: Chemical exposure, fate, and transfer to predators

Organochlorine contaminant concentrations, associated fugacities, and stable isotopes of nitrogen (δ(15) N) are reported for liver, whole body homogenate, and opportunistically collected samples of prey (amphipods), stomach oils, digestive tract contents, and guano for northern fulmars (Fulmarus glacialis) collected at Cape Vera, Devon Island in the Canadian High Arctic. Liver concentrations of polychlorinated biphenyls (ΣPCB) and ΣDDT were on average 49.9 ± 35.4 ng g(-1) and 29.9 ± 25.2 ng g(-1) wet weight, respectively. Whole body homogenate concentrations of ΣPCB and ΣDDT were 637 ± 293 ng g(-1) and 365 ± 212 ng g(-1) wet weight, respectively. A mass and energy balance showed that whole body contaminant concentrations, which are seldom reported for Arctic seabirds, are critical in determining contaminant exposure and associated risk to predators such as the Arctic fox (Alopex lagopus). Biomagnification in the fulmars is evident, because concentrations and fugacities of contaminants were generally one to three orders of magnitude higher than those of likely prey items. The fate of diet-derived contaminants along the digestive tract is discussed, in particular with respect to stomach oils, which are used to feed chicks and for defensive purposes. The benefits of considering both concentrations and fugacities are demonstrated and provide information on the absorption and distribution of chemicals within the fulmars and contaminant transfer to offspring and predators.

Temporal variability in organochlorine contamination in blood and blubber of captive Steller sea lions (Eumetopias jubatus)

AbstractThree adult captive Steller sea lions (SSL; two females, one male) housed in Alaska were longitudinally sampled for organochlorine contaminant (OC) analysis in both blubber (n= 19) and blood (n= 69) over a 2 yr period (March 2001 to March 2003). Blood OC concentrations were similar between individuals, and exhibited significant increases in summer months (July through September) relative to winter (January through March). Additionally, paired blood and blubber sample (n= 18) OC were significantly related for all animals. The relationship of blubber OC concentrations to lipid content was significant in all animals. Although limited to a small number of animals, our study results indicate that in SSLs, blood OC were both consistent among all animals and likely changed in association with physiologically driven metabolism of blubber.

Maternal transfer of chlorinated contaminants in the leatherback turtles, Dermochelys coriacea, nesting in French Guiana

We examined the maternal transfer of organochlorine contaminants (OCs), pesticides (DDTS and HCHs) and polychlorinated biphenyls (PCBs), and the temporal variation of blood and eggs concentrations from 38 leatherback turtles ( Dermochelys coriacea) nesting in French Guiana. PCBs were found to be the dominant OCs with respective mean concentrations of 55.14 ng g −1 lipid-mass for egg and 1.26 ng mL −1 wet-mass for blood. OC concentrations were lower than concentrations measured in other marine turtles which might be due to the lower trophic position (diet based on gelatinous zooplankton) and to the location of their foraging and nesting grounds. All OCs detected in leatherback blood were detected in eggs, suggesting a maternal transfer of OCs. This transfer was shown to depend on female blood concentration for ΣDDTs and for the most prevalent PCB congeners, since significant relationships were found between paired blood–egg concentrations. During the nesting season, OC concentrations in eggs and the percentage of lipid in eggs were found to decline in successive clutches, highlighting a process of offloading from females to their eggs and a decreasing investment of lipid from females into their clutches. OCs in eggs tended to be higher in females spending 3 years in the foraging grounds between two nesting seasons than in those spending 2 years, suggesting an impact of time spacing two breeding seasons, called remigration interval, and of location of the foraging grounds.

Geographical PCB and DDT Patterns in Shearwaters (Calonectrissp.) Breeding Across the NE Atlantic and the Mediterranean Archipelagos

Although seabirds have been proposed as useful biomonitors for organochlorine contaminants (OCs) in marine environments, their suitability is still unclear. To understand the geographic variability and the influence of seabird trophic ecology in OC levels, we analyzed PCBs, DDTs, delta(13)C, and delta(15)N in the blood of adult Calonectris shearwaters throughout a vast geographic range within the northeast Atlantic Ocean (from Cape Verde to Azores) and the Mediterranean Sea (from the Alboran Sea to Crete). OC concentrations were greater in birds from the Mediterranean than in those from the Atlantic colonies, showing higher and lower chlorinated PCB profiles, respectively. This large-scale pattern may reflect the influence of historical European runoffs in the Mediterranean basin and diffused sources for OCs in remote Atlantic islands. Spatial patterns also emerged within the Atlantic basin, probably associated with pollutant long-range transport and recent inputs of DDT in the food webs of shearwaters from Cape Verde and the Canary islands. Moreover, a positive association of OC concentrations with delta(15)N within each locality points out diet specialization as a major factor explaining differences in OCs at the intraspecific level. Overall, this study highlights wide range breeding seabirds, such as Calonectris shearwaters, as suitable organisms for biomonitoring large geographic trends of organochlorine contamination in the marine environment.

Organochlorine Pesticide and Polychlorinated Biphenyl in Feathers of Resident and Migratory Birds of South-West Iran

Persistent organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, hexachlorobenzene (HCB), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH) isomers, together with polychlorinated biphenyl (PCB) congeners (IUPAC Nos. 28, 52, 101, 138, 153, and 180) were determined in tail feathers from 35 birds belonging to 15 species, all originating from the southwest of Iran (Khuzestan, coast of the Persian Gulf) and kept in museum collections. The patterns of organochlorine contaminants (OCs) in birds varied depending on their migratory behavior. Resident birds contained higher median PCB concentrations (<LOQ-151 ng/g feather) than HCHs, DDTs, and HCB. Locally migrating birds had higher median concentrations of HCHs (19-83 ng/g feather). In contrast, long-distance migrants had lower concentrations of HCB and HCHs. A positive correlation was observed among OCs in these birds, suggesting that trophic level, feeding strategy, and taxonomic group are influencing factors for the OC concentrations in bird feathers. An estimate of the risk associated suggests that levels of OCPs and PCBs were lower or close to the threshold reported to affect reproduction in 1990s.

Organochlorine Contaminants in Water, Sediment and Fish of Lake Burullus, Egyptian Mediterranean Sea

Lake Burullus is one of the Delta lakes, connected with the Mediterranean Sea through El Boughaz opening. Concentrations of organochlorine contaminants were measured in water, sediments and biota of the lake because of concerns about their effects on its productivity. The concentrations of chlorinated hydrocarbons decreased in the order of PCBs > DDTs > TC > HCHs for all water samples collected from Lake Burullus during 2006. Higher concentrations were recorded during summer season, this clearly affected by higher agricultural and sewage activities. The concentrations of DDTs in water were ranged from 0.07 to 221.9 ng L(-1); 46.3-656.5 ng L(-1); 94.3-882.6 ng L(-1) and 24.8-233 ng L(-1) during winter, spring, summer and autumn, respectively. Among DDTs metabolites p,p-DDE was the most dominant with a maximum of 520.13 ng L(-1) recorded at station 10 (El Boughaz opening). In sediment samples, PCBs concentrations were ranged from 4.6 to 213.9 ng g(-1) with an average 47.2 ng g(-1); dry weight. Total pesticides were higher than PCBs for mostly all sediment samples of Lake Burullus. Concentrations of DDTs in fish tissues were ranged from 2.76 to 24.23 ng g(-1) and from 14.16 to 45.13 ng g(-1); wet weight for Oresochromus niloticus and Clarries sp., respectively.

Dietary biomagnification of organochlorine contaminants in Alaskan polar bears

Concentrations of organochlorine contaminants in the adipose tissue of polar bears ( Ursus maritimus Phipps, 1774) vary throughout the Arctic. The range in concentrations has not been explained fully by bear age, sex, condition, location, or reproductive status. Dietary pathways expose polar bears to a variety of contaminant profiles and concentrations. Prey range from lower trophic level bowhead whales ( Balaena mysticetus L., 1758), one of the least contaminated marine mammals, to highly contaminated upper trophic level ringed seals ( Phoca hispida (Schreber, 1775)). We used δ15N and δ13C signatures to estimate the trophic status of 42 polar bears sampled along Alaska’s Beaufort Sea coast to determine the relationship between organochlorine concentration and trophic level. The δ15N values in the cellular portions of blood ranged from 18.2‰ to 20.7‰. We found strong positive relationships between concentrations of the most recalcitrant polychlorinated biphenyls (PCBs) and δ15N values in models incorporating age, lipid content, and δ13C value. Specifically these models accounted for 67% and 76% of the variation in PCB153 and oxychlordane concentration in male polar bears and 85% and 93% in females, respectively. These results are strong indicators of variation in diet and biomagnification of organochlorines among polar bears related to their sex, age, and trophic position.

The potential impact of environmental variation on the concentrations and ecological effects of pollutants in a marine avian top predator

Concentrations of organochlorine contaminants (OCs) and associations between OCs and fitness components were examined in great black-backed gulls (Larus marinus) in three colonies along the coast of northern Norway. In one of the colonies, data were collected in two subsequent seasons. Concentrations of four OCs (HCB, oxychlordane, DDE and PCB) were measured in blood (n=260) and fitness components (reproductive variables and adult return rate between breeding seasons) were recorded. In the first year, in two of the colonies, body condition and reproductive performance among the gulls were poor compared to the third colony, suggesting spatial variation in environmental conditions, especially food availability. However, in the third colony, body condition and reproductive performance were even better in the second season; i.e. environmental conditions varied temporally. OC residues were higher in the colonies where environmental conditions were poor, but much of this variation was explained by differences in body condition among colonies. Moreover, concurrent with improved body condition from one season to the next, the concentrations of OCs were halved. In the two colonies where environmental conditions were poor, female OC residues were negatively related to egg-laying date, egg size and nesting success, and in the colony where the concentrations of OC were highest, gulls with elevated DDE residues had low probability of returning between breeding seasons. In comparison, in the colony where environmental conditions were better in the first year, other types of adverse relationships between OCs and fitness components were found; i.e. chicks from females with high OC concentrations were in poor condition at hatching, suggesting maternal transfer of OCs to the eggs, and males with high OC residues had poor nesting success and chick survival, suggesting OC-mediated behavioural changes. With improved environmental conditions and lower OC concentrations in the second season, no significant adverse relationships between OCs and fitness components were found. This study thus suggests that there are complex interrelationships between both concentrations and ecological effects of OCs, and the environment, indicating that effects of OCs in nature may only be assessed after considering environmental variation.

Reproductive performance and organochlorine pollutants in an Antarctic marine top predator: The south polar skua

Despite low levels of organochlorine contaminants (OCs) in Antarctic biota, some compounds may exceed the levels in equivalent Arctic species, and previous studies have found biochemical evidence of pollutant exposure in south polar skuas (Catharacta maccormicki), a common marine top predator in the region. In this study we examined relationships between fitness components (fecundity and adult return rate between breeding seasons) and concentrations of OCs in this species. In 65 nests, both males and females were caught, and using principal component analyses (PCA) we produced composite measurements (PC1 and PC2) of six highly correlated OCs measured in blood samples. Although the concentrations of OC were below those documented to have reproductive effects in other aquatic birds, we found that the eggs of females with high levels of OCs in the blood hatched later, and their chicks were in poorer condition at hatching, than females with low OC levels. Thus OCs may delay reproduction and reduce foetal growth in the skuas. However, there was no relationship between the parents' OC residues and the occurrence of non-viable eggs, although the proportion of nests containing non-viable eggs was high (47%). Moreover, there were no significant relationships between OCs and reproductive variables in males, even if males had higher OC levels than females, and no associations between OCs and adult return rate between breeding seasons.