I have studied persistent environmental pollutants in herring (Clupea harengus), in adult guillemot (Uria aalge) and in guillemot eggs from the Baltic Sea. The studied contaminants were organochlorines (OCs); dichlorodiphenyltrichloroethanes (DDTs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and brominated flame retardants (BFRs); polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD). The highest concentration in both species was shown by p,p′DDE with a concentration in guillemot egg (geometric mean (GM) with 95% confidence interval) of 18200 (17000 – 19600) ng/g lipid weight. The BFR with the highest concentration in guillemot egg was HBCD with a GM concentration of 140 (120 – 160) ng/g lw. To extract additional and essential information from the data, not possible to obtain using only univariate or bivariate statistics, I used multivariate data analysis techniques; principal components analysis (PCA), partial least squares regression (PLS), soft independent modelling of class analogy (SIMCA), and PLS discriminant analysis (PLS-DA). I found e.g.; that there are significant negative correlations between egg weight and the concentrations of HCB and p,p'DDE; that concentrations of OCs and BFRs in the organisms co-varied so that concentrations of OCs can be used to calculate concentrations of BFRs; and, that several contaminants (e.g. HBCD) had higher concentration in guillemot egg than in guillemot muscle, that several (e.g. BDE47) showed no concentration difference between muscle and egg and that one contaminant (BDE154) showed higher concentration in the guillemot muscles than in egg. In this thesis I developed a new method, “randomly sampled ratios” (RSR), to calculate biomagnification factors (BMFs) i.e. the ratio between the concentration of a contaminant in an organism and the concentration of the same contaminant in its food. With this new method BMFs are denoted with an estimate of variation. Contaminants that biomagnify are e.g., p,p′DDE, CB118, HCB, βHCH and all of the BFRs. Those that do not biomagnify are e.g., p,p′DDT, αHCH and CB101. Lastly, to investigate which of the contaminants descriptors (physical-chemical/other properties and characteristics) that correlates to the biomagnification of the contaminants, I modeled the contaminants’ respective BMFRSR versus ~100 descriptors and showed that ~20 descriptors in combination were important, either favoring or counteracting biomagnification between herring and guillemot.

The bioaccumulation of organic contaminants in aquatic ecosystems has been a key focus in environmental toxicology over the last decades. Bioaccumulation is a key concept in ecological risk assessments since it controls the internal dose of potential environmental contaminants. Information on the bioaccumulation of contaminants is used by regulatory authorities in the development of water quality standards, categorizing substances that are potential hazards and quantifying the risk of chemicals to human health. A basis for identifying priority chemicals has been the use of the octanol-water partition coefficient (KOW) as a criterion to estimate bioaccumulation potential. However, recognizing that the bioaccumulation process is not controlled by the hydrophobicity of a chemical alone, this thesis proposes a set of tools, incorporating chemical properties, environmental characteristics and physiological properties of organisms, to study the bioaccumulation of contaminants in aquatic ecosystems.  In striving to achieve this objective, a tool based on an equilibrium lipid partitioning approach was used in Paper I to evaluate monitoring data for bioaccumulation of organic contaminants. In Papers II and III, mechanistic based modelling tools were developed to describe bioaccumulation of hydrophobic compounds in aquatic food webs. In Paper IV, the bioaccumulation of organic compounds in aquatic food chains was studied using stable isotopes of nitrogen. The mechanistic fate and food web models developed in this thesis provide regulators and chemical manufacturers with a means of communicating scientific information to the general public and readily applicable mechanistic fate and food web models that are easily modified for evaluative assessments purposes.

The overall objective of this thesis was to determine selenium (Se) levels in the major compartments of aquatic ecosystems and correlate these data with potential Se effects on early life stages of two native fish species. This work was conducted at two uranium (U) mines located in northern Saskatchewan, Key Lake mine and McClean Lake mine. In addition, a site fidelity study was conducted at Key Lake mine to evaluate movement patterns of northern pike inhabiting lakes receiving effluent discharges.<p> At Key Lake mine, Se was accumulated and biomagnified several orders of magnitude higher than its concentration in water (0.7-2.7 µg/L) in lakes receiving discharges, with Se in prey organisms reaching levels above the proposed 3-11 µg/g dry weight (DW) dietary toxicity threshold for fish. Increased concentrations of Se in aquatic biota led to an increase in the Se concentrations in eggs and tissues of northern pike that rely on these organisms as food sources. Furthermore, increases in the incidence of Se-induced deformities above 30% were recorded in fry originating from adults exposed to high levels of dietary Se (> 3µg/g, DW). The increased frequency of deformities found in northern pike fry was associated with a significant increase in the level of Se in northern pike eggs from exposure sites (31.28 - 48.23 µg/g DW) compared to reference (3.19 ± 0.29 µg/g DW).<p> At McClean Lake mine, Se was accumulated and biomagnified through the aquatic food chain with concentrations in some biota groups (e.g., forage fish) exceeding the lower limit (> 3µg/g DW) of the 3-11µg/g (DW) threshold for dietary Se toxicity in fish. Although both northern pike and white sucker females collected from the exposure site showed greater levels of Se in egg and tissues compared to fish collected from a reference site (likely caused by exposure to elevated levels of Se in prey organisms), no increases in Se-induced deformities were found in the developing fish larvae. The lack of a toxic response in fish larvae is in agreement with Se thresholds for early life stage deformities, with egg Se concentrations in northern pike and white sucker collected at the exposure site below the proposed 10 µg/g (DW) threshold associated with the presence of developmental abnormalities. The applicability of the proposed 7.91 µg/g (whole body, DW) Se toxicity threshold to cold water fish is controversial given that most of the research has focused on warm water fish. Therefore, there is an urgent need to conduct studies that allow us to better understand the environmental fate and effects of Se in north temperate (cold water) aquatic systems. The results of my research will contribute valuable information for the establishment of a realistic and environmentally relevant Se threshold for the protection of fish populations in Canadian waters. During the site fidelity study, fish locations were seasonally and daily recorded using a Lotek SRX_400 receiver with handheld Yagi antenna. The results suggest that tagged pike did not migrate out of the study area throughout the study period, with the mean distance traveled ranging from 50 to 400 m. Differences in movement (distance traveled) and home range were found between reference and exposure sites. Overall data suggest that radio-telemetry is a useful tool in environmental studies. This information on northern pike behavior will be valuable towards developing non-lethal sampling methods that could be applied for assessing the effects of industrial discharges in north temperate aquatic ecosystems.

The overall objective of this thesis was to determine selenium (Se) levels in the major compartments of aquatic ecosystems and correlate these data with potential Se effects on early life stages of two native fish species. This work was conducted at two uranium (U) mines located in northern Saskatchewan, Key Lake mine and McClean Lake mine. In addition, a site fidelity study was conducted at Key Lake mine to evaluate movement patterns of northern pike inhabiting lakes receiving effluent discharges.<p> At Key Lake mine, Se was accumulated and biomagnified several orders of magnitude higher than its concentration in water (0.7-2.7 µg/L) in lakes receiving discharges, with Se in prey organisms reaching levels above the proposed 3-11 µg/g dry weight (DW) dietary toxicity threshold for fish. Increased concentrations of Se in aquatic biota led to an increase in the Se concentrations in eggs and tissues of northern pike that rely on these organisms as food sources. Furthermore, increases in the incidence of Se-induced deformities above 30% were recorded in fry originating from adults exposed to high levels of dietary Se (> 3µg/g, DW). The increased frequency of deformities found in northern pike fry was associated with a significant increase in the level of Se in northern pike eggs from exposure sites (31.28 - 48.23 µg/g DW) compared to reference (3.19 ± 0.29 µg/g DW).<p> At McClean Lake mine, Se was accumulated and biomagnified through the aquatic food chain with concentrations in some biota groups (e.g., forage fish) exceeding the lower limit (> 3µg/g DW) of the 3-11µg/g (DW) threshold for dietary Se toxicity in fish. Although both northern pike and white sucker females collected from the exposure site showed greater levels of Se in egg and tissues compared to fish collected from a reference site (likely caused by exposure to elevated levels of Se in prey organisms), no increases in Se-induced deformities were found in the developing fish larvae. The lack of a toxic response in fish larvae is in agreement with Se thresholds for early life stage deformities, with egg Se concentrations in northern pike and white sucker collected at the exposure site below the proposed 10 µg/g (DW) threshold associated with the presence of developmental abnormalities. The applicability of the proposed 7.91 µg/g (whole body, DW) Se toxicity threshold to cold water fish is controversial given that most of the research has focused on warm water fish. Therefore, there is an urgent need to conduct studies that allow us to better understand the environmental fate and effects of Se in north temperate (cold water) aquatic systems. The results of my research will contribute valuable information for the establishment of a realistic and environmentally relevant Se threshold for the protection of fish populations in Canadian waters. During the site fidelity study, fish locations were seasonally and daily recorded using a Lotek SRX_400 receiver with handheld Yagi antenna. The results suggest that tagged pike did not migrate out of the study area throughout the study period, with the mean distance traveled ranging from 50 to 400 m. Differences in movement (distance traveled) and home range were found between reference and exposure sites. Overall data suggest that radio-telemetry is a useful tool in environmental studies. This information on northern pike behavior will be valuable towards developing non-lethal sampling methods that could be applied for assessing the effects of industrial discharges in north temperate aquatic ecosystems.

Elevated polychlorinated biphenyl (PCB) concentrations have been detected in marine mammals inhabiting the Strait of Georgia, British Columbia (Canada) and Puget Sound, Washington State (USA). This raises concerns about adverse health effects and underscores the importance of documenting source, transport, and fate of contaminants. This marine mammal-oriented study- (1) examines dietary exposure to complex mixtures of persistent organic pollutants (POPs); (2) characterizes POP accumulations using congener-specific contaminant analyses, stable isotope ratios, and multivariate statistical methods; and (3) explores some of the influencing factors for POP bioaccumulation in marine mammals. A first application of a food basket approach to assessing real-world dietary exposure to mixtures of chemicals in marine mammals has revealed Puget Sound as a regional “hotspot” for PCB contamination. The consistency between PCB concentrations in Puget Sound and the Strait of Georgia harbour seals (Phoca vitulina) and their food baskets validates the use of this method as a basis for exploring dietary exposure, metabolism, biomagnification, and health risks in marine mammals. Concentration rankings of POPs and estimated daily intakes based on our food baskets suggests that both legacy (e.g., PCB, dichlorodiphenyltrichloroethane [DDT]) and new (polybrominated diphenyl ethers [PBDEs]) POPs may pose potential health risks to seals. Accumulations of PCBs in the Strait of Georgia seal food web demonstrate the bioaccumulative nature and persistence of PCBs. Correlations of PCB concentrations with physicochemical properties and trophic level revealed the important role that metabolism plays in biomagnification in seals, alongside trophic level and log Kow. We estimate a PCB load of 77 kg within the Strait of Georgia biomass, with the largest proportion (36 %) detected in marine mammals. Dietary exposure of POPs to resident killer whales (Orcinus orca) was assessed by measuring POPs in four stocks of chinook salmon (Oncorhynchus tshawytscha), their primary prey. Differences in POP concentrations between chinook smolts and returning adults suggest that the majority of POPs are acquired at sea during the major growth period in their life cycle. Higher POP concentrations and low lipid content were observed among the more southerly stocks suggesting a migration-associated metabolism and loss of lighter congeners, thereby exposing southern residents to more highly contaminated chinook salmon. Consumption on a lipid-weight basis, (higher consumption on a wet weight basis), as well as consuming prey from a more contaminated region, likely increases killer whale exposure to POPs, offering an explanation for higher contaminant burdens in southern residents. While previous research has examined species inhabiting different trophic levels or food chains in other regions, this study has provided an assessment of POP dietary exposure, biomagnification, and influencing factors on trophic accumulations in a North-eastern Pacific marine mammal food web. These results have provided further insight into the influence of such factors as age, sex, lipid content, diet, migration-related metabolism, physicochemical properties (degree of chlorination, log Kow), and chemical structure on POP accumulation in marine mammals. We have identified the largely unregulated PBDEs as posing potential health risks to marine mammals and offered a means to update existing tissue residue guidelines for the protection of wildlife.

Title from first page of PDF document. Includes bibliographical references (p. 24-30).

Made available in DSpace on 2014-06-11T19:30:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-23Bitstream added on 2014-06-13T20:21:10Z : No. of bitstreams: 1 farias_ra_dr_jabo.pdf: 809420 bytes, checksum: 5a9750b5ac70ff565c70abad88e736c8 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A região amazônica foi alvo de intensa atividade garimpeira nas décadas de 80 e 90. Esta atividade vinculada à utilização intensiva de mercúrio no processo de amalgamação do ouro, gerou uma preocupação mundial com a região, uma vez que acidentes com mortes e seqüelas já ocorreram em países ao redor do mundo devido à exposição direta e indireta ao mercúrio A presença do mercúrio antropogênico no ambiente amazônico, com possíveis contaminações dos seus ecossistemas aquáticos, e conseqüente contaminação dos peixes preocupa, principalmente sendo estes, uma das principais vias de acesso aos seres humanos na exposição indireta ao metal. Esta preocupação aumenta ainda mais, uma vez que os peixes na Amazônia são a principal fonte protéica para ribeirinhos e pequenos produtores rurais. Assim se torna necessário, além da determinação dos níveis de mercúrio, a identificação de propostas práticas para mitigar os riscos a saúde das populações da região. Este estudo apresenta tópicos relacionados ao mercúrio na Amazônia brasileira, caracterizando seu ciclo biogeoquímico e a presença deste metal na biota aquática, enfocando inicialmente a contaminação de peixes por mercúrio nos ecossistemas naturais, e posteriormente insere a piscicultura, de sistemas semi intensivo e intensivo, como uma nova prática de mitigação para os possíveis danos a saúde humana, decorrente da ingestão de peixes. A inserção da piscicultura nesta temática, segue basicamente o conceito de que, uma vez bem manejada, a piscicultura limita os fatores da transformação do mercúrio metálico, quando presente no ambiente, para o metil mercúrio, a forma tóxica do metal e meio de entrada na cadeia trófica. / The amazonian region was the object of intensive gold explotaitaion in the 1980's and 90's. The intensive use of mercury in the amalgamation process became a worldwide concern as the aftereffects of direct and indirect mercury exposure were becoming apparent in other countries. The presence of anthropogenic mercury in the Amazonian environment, related to possible contamination of its aquatic ecosystems and imminent fish contamination, is an issue of high concern largely because food contamination is one of the main ways of human contamination. This concern increases due to the fact that amazonian fishes are the main protein source for the rural inhabitants. As such, it is necessary to determine the actual levels of mercury in the fishes and identify practical ways of mitigating health risks to the local population. This study exposes the problem of mercury contamination on fish in the Brazilian Amazon by describing mercury's biogeochemical cycle and its presence in the aquatic biota, initially focusing on the contamination of fish by mercury through bioaccumulation and biomagnification in natural ecosystems. The study finally proposes intensive and semi-intensive fish farming as a new activity to be taken into account to mitigate the harmful risks to human health due to ingestion of Amazonian fish. The rational of using fish farming as a mitigation activity is that once it is well managed, fish farming limits the transformation factors of mercury to its toxic form, metal mercury, and its pathway into the trophic chain.

Resumo: A região amazônica foi alvo de intensa atividade garimpeira nas décadas de 80 e 90. Esta atividade vinculada à utilização intensiva de mercúrio no processo de amalgamação do ouro, gerou uma preocupação mundial com a região, uma vez que acidentes com mortes e seqüelas já ocorreram em países ao redor do mundo devido à exposição direta e indireta ao mercúrio A presença do mercúrio antropogênico no ambiente amazônico, com possíveis contaminações dos seus ecossistemas aquáticos, e conseqüente contaminação dos peixes preocupa, principalmente sendo estes, uma das principais vias de acesso aos seres humanos na exposição indireta ao metal. Esta preocupação aumenta ainda mais, uma vez que os peixes na Amazônia são a principal fonte protéica para ribeirinhos e pequenos produtores rurais. Assim se torna necessário, além da determinação dos níveis de mercúrio, a identificação de propostas práticas para mitigar os riscos a saúde das populações da região. Este estudo apresenta tópicos relacionados ao mercúrio na Amazônia brasileira, caracterizando seu ciclo biogeoquímico e a presença deste metal na biota aquática, enfocando inicialmente a contaminação de peixes por mercúrio nos ecossistemas naturais, e posteriormente insere a piscicultura, de sistemas semi intensivo e intensivo, como uma nova prática de mitigação para os possíveis danos a saúde humana, decorrente da ingestão de peixes. A inserção da piscicultura nesta temática, segue basicamente o conceito de que, uma vez bem manejada, a piscicultura limita os fatores da transformação do mercúrio metálico, quando presente no ambiente, para o metil mercúrio, a forma tóxica do metal e meio de entrada na cadeia trófica. / Abstract: The amazonian region was the object of intensive gold explotaitaion in the 1980's and 90's. The intensive use of mercury in the amalgamation process became a worldwide concern as the aftereffects of direct and indirect mercury exposure were becoming apparent in other countries. The presence of anthropogenic mercury in the Amazonian environment, related to possible contamination of its aquatic ecosystems and imminent fish contamination, is an issue of high concern largely because food contamination is one of the main ways of human contamination. This concern increases due to the fact that amazonian fishes are the main protein source for the rural inhabitants. As such, it is necessary to determine the actual levels of mercury in the fishes and identify practical ways of mitigating health risks to the local population. This study exposes the problem of mercury contamination on fish in the Brazilian Amazon by describing mercury's biogeochemical cycle and its presence in the aquatic biota, initially focusing on the contamination of fish by mercury through bioaccumulation and biomagnification in natural ecosystems. The study finally proposes intensive and semi-intensive fish farming as a new activity to be taken into account to mitigate the harmful risks to human health due to ingestion of Amazonian fish. The rational of using fish farming as a mitigation activity is that once it is well managed, fish farming limits the transformation factors of mercury to its toxic form, metal mercury, and its pathway into the trophic chain. / Orientador: Roberto Goitein / Coorientadora: Sandra de Souza Hacon / Banca: Claudinei da Cruz / Banca: Alfredo Martins Paiva Filho / Banca: Augusto Shinyia Abe / Banca: Isabella Braz Cardone / Doutor

Os estudos realizados em diversas partes do mundo sobre a utilização de pesticidas e os impactos que estes podem causar ao ambiente são uma das ações prioritárias para o desenvolvimento da agricultura, principalmente para aqueles pesticidas que são persistentes ao meio biótico e abiótico, como o inseticida heptacloro, que apesar de seu uso restrito para tratamento de madeira, ainda é muito usado no Brasil clandestinamente para outros fins. A maioria dos estudos realizados até agora sobre biomagnificação envolve o meio terrestre e uma pequena porcentagem desses é direcionada para o meio aquático e tem sido realizada em modelos de campo. O objetivo deste projeto foi determinar a CL50 96 horas para peixes a acumulação, biomagnificação e depuração do heptacloro em um modelo de sistema aquático. Como não existe nenhuma norma que defina o efeito cumulativo através dos níveis tróficos, pretendeu-se com esta pesquisa estimar a biomagnificação e depuração do heptacloro. Este estudo foi realizado em laboratório, em um modelo dividido em compartimentos individualizados, no qual somente as algas (Pseudokirchneriella subcapitata) foram submetidas por um período de 7 dias ao heptacloro, obtendo-se uma concentração final de 0,10 x 10-5µg heptacloro/µg algas, as quais posteriormente serviram de alimento para os microcrustáceos (Daphnia magna) durante 9 dias, que ao final concentraram 0,12 x 10-5 µg heptacloro/µg organismos. Por último, os peixes (Danio rerio) foram alimentados com microcrustáceos, no período de 5 dias, alcançando uma concentração final de 0,62 x 10-8 µg heptacloro/µg organismos. Nos últimos 9 dias, durante o período de depuração, os peixes foram alimentados em dias intercalados com microcrustáceos e ração sem contaminação com o produto, atingindo uma concentração final de 0,25 x 10-8 µg heptacloro/µg organismos. Nos testes realizados com esses três organismos, observou-se que a concentração ficou maior conforme o nível dentro do modelo proposto era mais alto, comprovando assim a hipótese do poder de bioacumulação, biomagnificação e depuração do heptacloro. / The studies carried out in different parts of the world about the pesticides use and the impacts that they can cause to the environment, are one of the priority actions for the agriculture development, mainly for those pesticides that are persistents in the biotic and abiotic environment, such as the heptachlor insecticide, which is still illegally used for others purposes in Brazil, although its use is limited for the wood treatment. The majority of the studies carried out until now about biomagnification involves the terrestrial environment and a small percentage of these studies are directed for the aquatic environment, and this small percentage has been carried out in field models. The aim of this project was to determine the LC50 96 hours for fish, accumulation, biomagnifications, and depuration of heptachlor in an aquatic system model and, as there isn?t any norm that defines the cumulative effect through trophic levels, it was claimed with this research to esteem the heptachlor biomagnification and depuration. This study was carried out in a laboratory, in a model divided in single chambers, in which the algae (Pseudokirchneriella subcapitata were submitted during 7 days to the heptaclhor, getting a final concentration of 0.10 x 10-5µg heptaclhor/µg algae, which was later served as food for the microcrustaceans (Daphnia magna) were submitted during 7 days to the heptaclhor, getting a final concentration of 0.10 x 10-5Mµg heptaclhor/µg algae, which was later served as food for the microcrustaceans (Daphnia magna) were fed with microcrustaceans, in the period of 5 days, reaching a final concentration of 0.62 x 10-8 µg heptaclhor/µg organisms. In the last 9 days, during the period of depuration, the fish were fed in days intercalated with microcrustaceans and ration without contamination with the product, reaching a final concentration of 0.25 x 10-8 µg heptacloro/µg organisms. In tests carried out with these three organisms, it was observed that the concentration was bigger as higher the level inside of the considered model, thus proving the hypothesis of the bioaccumulation, biomagnification, and depuration power of heptachlor.

La compréhension des mécanismes de bioaccumulation des contaminants organiques persistants (POP) dans les réseaux trophiques marins est un enjeu majeur pour l'évaluation des risques environnementaux liés aux pressions anthropiques, notamment en zone côtière. Le plancton joue un rôle pivot dans le devenir des PCB dans l'environnement marin, notamment sur la base des observations de fortes concentrations de ces contaminants chez les zooplanctonophages. Les processus d'accumulation de ces contaminants au sein du plancton restent mal connus. Dans le cadre du projet COSTAS, les teneurs en PCB dans trois classes de tailles de plancton ont été étudiées en baie de Marseille entre sept. 2010 et oct. 2011. Les concentrations étaient fortes en comparaison à d'autres mesures réalisées dans le golfe du Lion. Du fait des apports variables en PCB, aucun «effet de dilution par la biomasse» n'a pu être détecté. Le niveau de contamination est fortement corrélé aux conditions météorologiques qui augmentent les concentrations en PCB dans l'eau. Le passé récent des organismes planctoniques, caractérisable par leur taille ou leur teneur en lipides, ne montre pas d'influence sur les teneurs observées. Le rapport C/N met en évidence l'importance de la contribution des détritus dans les niveaux de contaminations des différentes classes de taille. Une bioamplification modérée mais significative avec la position trophique est mise en évidence par les signatures de δ15N. La relation linéaire entre les BAF et log Kow indiquerait que le partage à l'équilibre avec la phase aqueuse suffit à contrôler les niveaux de PCB dans le plancton. / The understanding of bioaccumulation mechanisms of persistent organic pollutants (POP) in marine trophic networks is a major issue for scaling environmental risks linked to anthropogenic pressure, particularly in coastal areas. The plankton is assumed to play a pivotal role in the fate of PCBs in marine environment, as highlighted by the high concentrations found in planktivorous predators. However the accumulation processes of these contaminants in plankton are still poorly documented. The COSTAS project aimed at improving our knowledge on this issue. PCB levels in three plankton size-classes were studied in the bay of Marseilles (N-W Mediterranean Sea), between September 2010 and Octobre 2011. Measured PCB concentrations in Marseille bay plankton were high in comparison to those measured in other areas of the Gulf of Lion. No "dilution effect" was detected, due to the high variability in PCB inputs in the bay.receive, . The level of contamination in plankton appeared directly linked to weather conditions which increase the PCB concentration either through continental inputs or by sediment re-suspension events and hydrodynamic transport. The recent history of plankton organisms, derived from their size or their lipid content, had no influence on their PCB concentrations. The C/N ratio highlights the contribution of detritus in driving the contamination levels measured in the various size-classes. A moderate but significant bioamplification through planktonic trophic levels was highlighted using δ 15N signatures. The linear relationship between BAF and log Kow would indicate that the equilibrium with water phase is sufficient to control the PCB levels in the plankton.