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Program Title: Aquatic Contaminants - Fiscal Year 1996/1997
This research program combines process studies and mathematical modeling focused on toxic organic contaminants to increase our understanding of the dynamics and effects of pollutants in the ecosystem.
Task Leader: Peter Landrum, 734-741-2276, Peter.Landrum@noaa.gov
Aquatic Contaminants Program Main Page
Persistent contaminants introduced into the ecosystem bind to particles and either remain suspended in the water column (particle-associated contaminants) or settle into the sediment (sediment-associated contaminants). Aquatic bottom-dwelling organisms (benthos) are exposed to certain critical pollutants through their contact with the sediment. These pollutants may then be introduced into the lower food chain, from which they can be transferred up the aquatic food web, ultimately fish, and threaten human health as well as the health of the ecosystem.
GLERL's Aquatic Contaminants Research focuses on organic contaminants in the Great Lakes and coastal marine environments. Considerable progress has been made over the last 25 years in reducing inputs of toxic pollutants to the aquatic environment through point-source control. This control technique has resulted in detectable decreases in contaminants levels in both fish and recently deposited surface sediments, especially in the Great Lakes ecosystem. However, the success of point-source controls has elevated the importance of secondary sources of contaminants, such as atmospheric deposition, non-point-source runoff, and release from contaminated sediments. These are now the most prevalent sources of contaminants entering the aquatic food web. Therefore, despite the great improvements in reducing toxics from point-sources, toxic contaminants from these secondary sources continue to cause problems, such as reproductive failure in lake trout and fish-eating birds and mammals, deformities in the offspring of fish-eating birds, and possible effects on human reproduction for heavy consumers of Great Lakes fish.
GLERL's past research primarily focused on the transport and fate of toxic organic contaminants in the ecosystem - on the routes, pathways, and processes by which organisms are exposed to these contaminants, and how these contaminants enter and move within the aquatic food web. Our research in the early 1980s demonstrated the importance of sediments in the Great Lakes as long-term, capacitor-like sources of contaminants. We have shown that it can take in excess of 100 years for a particle-associated contaminant recently introduced into the Great Lakes to be buried to the point of removing it from the ecosystem. Because of the potential for long-term inputs from sediments, the factors that influence the bioavailability of sediment-associated contaminants to the lower food web have been a focus of GLERL's recent research. The lower food web is the major pathway for reintroduction of these contaminants into the aquatic community. Food web transport of contaminants in the Great Lakes has recently gained added significance because of the changes in ecosystem structure brought about by the invasion of nonindigenous species, especially the zebra mussel, in the late 1980s.
This research program has also improved hazard assessment for contaminated sediments by exploring and revealing the limitations of existing methodologies for evaluating the hazard level associated with a contaminated sediment. It has become clear that trying to evaluate the exposure of benthic organisms to contaminants in sediments using the standard approach, which is to measure the contaminant concentration in the external environment, is not satisfactory. GLERL's research has shown that exposure to sediment-associated contaminants depends on the composition of the sediment, the characteristics of the toxin, and the behavior and physiology of the organism. Benthic organisms exhibit a wide range of feeding behaviors, ranging from filtering the overlying water (most bivalves) to general sediment ingestion (oligochaete worms). As a result, not all benthos receive equivalent exposures.
Project Index GLERL 06 - Aquatic Contaminants
- Bioaccumulation of Organic Contaminants by Diporeia spp.: Kinetics and Factors Affecting Bioavailability
- Measurement of Select Toxic Organic Contaminants in Surficial Sediments of Lake Michigan: Estimation of Lakewide Inventories and Seasonal Settling Fluxes
- Contaminant Effects and the Relationship to Exposure(GLERL funding)/Testing Equilibrium Partitioning and Residue-Based Measures for Sediment-associated Contaminants. (EPA Funding)
- Sampling the Resuspendible Pool of Sediments and Associated Contaminants and Measuring Mass and Contaminant Fluxes in Lake Michigan Using Sediment Traps
- Long-Term Trends in Benthic Populations
- Bioavailability of Sediment-Associated Toxic Organic Contaminants
- Trophic transfer of atmospheric and sedimentary contaminants into Great Lakes fish: controls on ecosystem scale response times
[RETURN to FY96/97 Accomplishments and Plans Cover Page] [RETURN to Research Overview page] [RETURN to GLERL home page]
ERL Research Task: GLERL 6 - Aquatic Contaminants
Bioaccumulation of Organic Contaminants by Diporeia spp.: Kinetics and Factors Affecting Bioavailability
Principal Investigator: Peter Landrum (734-741-2276; peter.landrum@noaa.gov)
Collaborating Scientists: Michelle Gedeon (CILER-University of Michigan); Duane Gossiaux (GLERL)
Accumulation of contaminants by benthic organisms may occur several ways: (1) by ingestion of sediment particles, (2) by respiration of the interstitial water, (3) by respiration of the overlying water, (4) by ingestion of freshly deposited food particles, and/or (5 through physical contact with any of the above. Resolving the factors and routes of accumulation are necessary to develop accurate predictions of bioaccumulation (amount of contaminant that accumulates in an organism). Recent attempts to include the benthic food web in bioaccumulation models indicate that benthos contribute significantly to the food web transfer of organic contaminants. Attempts to model the bioaccumulation of polycyclic aromatic hydrocarbons (PAH) by Diporeia, a major benthic food web component in the Great Lakes, suggests that there are substantial seasonal changes in the concentration of contaminants, but these seasonal changes have not yet been incorporated into more complex food chain models. This work focuses on how temperature, sediment composition, and feeding on fresh detritus affect bioaccumulation in benthic organisms.
This project also provides specific data related to the needs of the EPA-sponsored Lake Michigan Mass Balance Study (LMMB), which seeks to determine a mass balance of inputs and outputs of select contaminants for Lake Michigan and to predict their concentrations in the upper food web. The LMMB Study is designed to answer questions posed in the amended Clean Air Act, and to assist environmental managers in developing and implementing the Lake Michigan Lakewide Management Plan.
FY96 Progress and Accomplishments
Toxicokinetic data for the accumulation of selected polychlorinated biphenyl congeners were determined for the amphipod, Diporeia spp., as part of the LMMB Study. The impact of environmental and physiological factors, temperature and organism size, on accumulation from both water and sediment were measured. The size of the organism greatly affects the uptake from both media. However, temperature has a lessor effect for accumulation from sediment. This is the first study to investigate the role of these variables on the accumulation of these contaminants from sediment.
Bioaccumulation experiments with PCB congeners in sediments at selected temperatures were completed; and water and sediment bioaccumulation experiments where data were found to be inconsistent were repeated.
FY97 Plans
- Determine the relationship between temperature, organism size and accumulation kinetics for Diporeia spp. from laboratory measured toxicokinetics to predict toxicant accumulation in this lower food web organism.
- Complete draft report to the U.S. EPA on the relationship between temperature, organism size and accumulation kinetics for selected PCB congeners.
Measurement of Select Toxic Organic Contaminants in Surficial Sediments of Lake Michigan: Estimation of Lakewide Inventories and Seasonal Settling Fluxes
Principal Investigator: Patricia Van Hoof
Collaborating Scientists: Sander Robinson, Jui-Lan Hseih, Jeffrey Johnson (CILER-University of Michigan)
This project provides specific data related to the needs of the EPA-sponsored Lake Michigan Mass Balance Study (LMMB), and also the EPA-sponsored Environmental Monitoring and Assessment Program (EMAP). The LMMB Study seeks to determine a mass balance of inputs and outputs of select contaminants for Lake Michigan. The study is designed to answer questions posed in the amended Clean Air Act, and to assist environmental managers in developing and implementing the Lake Michigan Lakewide Management Plan. The goal of EMAP is to estimate the current status, trends, and changes in the Nation's ecological resources. More specifically, the program in Lake Michigan seeks to determine the areal extent of sub-nominal conditions in the nearshore zone. Status and spatial trends in the benthic community have been identified as the primary environmental indicator. Supplemental indicators include sediment toxicity (as determined by bioassay) and concentrations of organic contaminants.
The purpose of this project is to provide an inventory of critical contaminants (PCBs and trans nonachlor) in the Lake Michigan surface sediments. Contaminant deposition zones, hot spots, and local sources will be identified using trace organic contaminant concentration maps and sediment inventories. In addition, the seasonal transport of contaminants between regions of the water column, and between the water column and surface sediment will be estimated from sediment trap collections.
To test the applicability of the Equilibrium Partitioning model for assessing contaminant bioaccumulation in Lake Michigan benthic invertebrates, Diporeia spp. were collected at 72 LMMB/EMAP stations. Accumulation of PCBs, chlorinated pesticides and PAHs will be examined to determine controlling factors, such as, organism size, organism lipid content, sediment composition, sediment contamination and compound hydrophobicity.
FY96 Progress and Accomplishments
Of the 125 surface sediment samples collected at EMAP stations in July, 1994, 101 have been extracted and 65 analyzed for PCBs and transnonachlor. 45 sediment samples were analyzed for organic contaminants and organic carbon content and reviewed for quality control. Of the 72 Diporeia spp. samples collected at these EMAP stations, 58 have been analyzed for PCBs and lipid content and BSAFs calculated.
The third and final year of field sampling for the LMMB Study was completed. A spring 1996 cruise involved completing collections for the LMMB Study as well as sampling select transitional, depositional and nondepositional regions for analysis of nutrients, trace organic contaminants, and radionuclides on size-fractionated sediments (<20 microns, 20-65 microns, >65 microns).
Developed a sediment size-fractionation method that was verified with laser light-scattering particle sizing. Size fractionated the sediments collected at 6 stations in southern Lake Michigan for contaminant and organic carbon analyses.
Analysis for trace organic contaminant residues (PCBs, chlorinated pesticides, and PAHs) in 58 of the 72 Diporeia spp. samples collected at LMMB/EMAP stations were completed. Spatial variability of PCB bioaccumulation at station depths <80m was examined for animals >3 mm in length. The relationships of PCB congener log K ow to Biota/Sediment Accumulation Factors (BSAF, normalized for tissue lipid and sediment organic carbon) were notably different in northern versus southern regions of Lake Michigan. At northern stations, where amphipod lipid fractions were approximately 30-40%, BSAFs increased with log Kow values, then plateau in the superhydrophobic range (>6.5). In contrast, at most southern stations, where lipid fractions averaged 16-25%, BSAFs were generally higher and continued to increase with log Kow even for superhydrophobic congeners. Despite lipid normalization, BSAFs reflect a further relationship with organism lipid content. Spatial variability of the quality and/or amount of the amphipods' food source will be investigated as a potential determinant of lipid content as well as contaminant residues.
FY97 Plans
- Analyze LMMB trap samples to obtain PCB, PAH and organochlorine pesticide fluxes to depositional and nondepositional regions of Lake Michigan. Trap particulate matter will also be examined as a mechanism for delivery of contaminants to the benthic amphipod Diporeia spp.
- Analyze 5-8 high resolution cores for depth profiles of PCBs, PAHs, and organochlorine pesticides. The profiles will be used to determine bed sediment inventories and historical fluxes to depositional regional of Lake Michigan.
- Size-fractionated sediment at 5 sites (depositional and nondepositional) in southern Lake Michigan will be analyzed for PCBs, PAHs, and organochlorine pesticides. Transport of particulate-associated contaminants and their bioaccumulation by benthos is a function of particle size. Measurements of this kind are scarce but necessary to improve our understanding and our models of the fate and transport hydrophobic organic pollutants.
- Toxaphene is emerging as a pesticide mixture of concern in northern Lake Michigan and Lake Superior sportfish. In collaboration with Deborah Swackhamer of the University of Minnesota, extracts from LMMB cores will be analyzed for toxaphene using electron capture negative ionization (ECNI) gas chromatography/mass spectrometry (GC/MS). Evidence of regional sources and signal response to the 1982 ban will be examined.
- Complete analysis of Diporeia spp. samples collected at LMMB 1995 stations (offshore) and generate bioaccumulation factors using bed sediment and trapped particulate matter as food sources. Preliminary data from EMAP stations (nearshore) suggest a south-north trend of increasing bioaccumulation by these amphipods for lower molecular weight PCBs and PAHs. Statistical analysis of environmental parameters, such as sediment contamination, grain size, sediment organic carbon and nitrogen content, organism lipid level and composition, will be examined to explain spatial differences in bioavailability.
- Submit surficial sediment, trap and core data to USEPA-Great Lakes Program Office, along with appropriate quality control/quality assurance data.
Contaminant Effects and the Relationship to Exposure(GLERL funding)/Testing Equilibrium Partitioning and Residue-Based Measures for Sediment-associated Contaminants. (EPA Funding)
Principal Investigator: Peter Landrum (734-741-2276; peter.landrum@noaa.gov) Collaborating Scientists: Susan Fisher (Ohio State University); Duane Gossiaux (GLERL)
The goal of this project is to explore the relationship between contaminant exposure and contaminant effects on biota. To accomplish this goal, new procedures (bioassays) will be developed to determine the body burdens (concentration of the contaminant that builds up in the organism's body) required to produce measurable effects in specific biota.
FY96 Progress and Accomplishments
The utility of EPA's Equilibrium Partitioning Approach and the critical body residue approach were investigated for assessing contaminant exposure from sediments. The toxicity of fluoranthene to Diporeia spp. and Hyalella azteca were better evaluated through the use of the critical body residue approach. The Equilibrium Partitioning Approach did not readily predict the toxicity of sediment associated fluoranthene for either species. However, based on the body residue the toxicity occurred when the concentrations exceeded approximately 2 mol per gram wet weight.
Feeding organisms during sediment bioassay exposures has been considered problematic as it was expected to change the potential exposure to the sediment-associated contaminants. In a study of Hyalella azteca exposures to sediment-associated fluoranthene, the organisms fed low levels of uncontaminated food actually accumulated greater doses and were less sensitive to the effect of the toxin than those that were not fed. Thus, feeding uncontaminated food will not necessarily reduce exposure to the sediment-associated contaminants. The reduced toxicity was thought to result from the improved health of the fed organisms. Thus, the current protocol for performing toxicity bioassays on sediments may underestimate the toxicity of the associated contaminants while over estimating exposure.
The critical body residue approach is being studied for its utility in chronic exposures, including whole life-cycle for midges. This work is developing the methods for determining the experimental designs for chronic exposures. These studies have demonstrated differences in residue-affects levels between contaminants presumably resulting from differing mechanisms of action. Further, the approach demonstrates that different species of aquatic benthos are significantly more sensitive to some contaminants and specifically more susceptible to compounds when mechanisms of action other than narcosis are important in the toxic action.
Products
Ingersoll, C.G., G.T. Ankley, D.A. Benoit, E.L. Brunson, G.A. Burton, F.J. Dwyer, R.A. Hoke, P.F. LANDRUM, T.J. Norberg-King, and P.V. Winger. 1995. Toxicity and bioaccumulation of sediment-associated contaminants using freshwater invertebrates: A review of methods and applications. Environ. Toxicol. Chem. 14:1885-1894.
FY97 Plans
- Improve assessment of bioaccumulation through the development of data on residue concentrations required to produce toxic effects particularly for chronic endpoints.
- Evaluate EPA's Equilibrium Partitioning approach for evaluating toxicity of sediment-associated contaminants through selected experiments to Diporeia spp. and Hyalella azteca.
Sampling the Resuspendible Pool of Sediments and Associated Contaminants and Measuring Mass and Contaminant Fluxes in Lake Michigan Using Sediment Traps
Principal Investigator: Brian Eadie (734-741-2281; brian.eadie@noaa.gov)
Collaborating Scientists: John Robbins, Patricia Van Hoof (GLERL); Douglas Endicott, Ronald Rossman (EPA/ORD-Grosse Ile); Thomas Johengen (CILER-University of Michigan)
Since 1977, GLERL has examined the processes of particle flux and resuspension through the use of sediment traps. We have learned much about the transport of mass, contaminants, and tracers, and the results are now routinely incorporated into program sampling, modeling strategies, and management considerations.
In the Great Lakes, the largest fraction of persistent trace contaminants reside in the sediments due to sorption and settling processes. Studies of the long-term behavior of fallout radionuclides and stable contaminants in the Great Lakes have shown that higher levels exist in the lakes than expected if settling and burial were the only transport processes. Materials are resuspended into the water column from sediments and are then consumed by biota. It is now accepted that this recycling, caused by the processes of bioturbation and resuspension, is responsible for the continued high levels of trace contaminants (e.g. PCB, DDT) in fish and the slow response of the lakes to abatement of contaminant inputs.
This project also provides specific data related to the needs of the EPA-sponsored Lake Michigan Mass Balance Study (LMMB), which seeks to determine a mass balance of inputs and outputs of select contaminants for Lake Michigan. The LMMB Study is designed to answer questions posed in the amended Clean Air Act, and to assist environmental managers in developing and implementing the Lake Michigan Lakewide Management Plan.
FY96 Progress and Accomplishments
Of the potential total of 250 trap samples, we have collected 120 and 46 are still in the lake. All of the retrieved samples have been split in half, one portion going for PCB analysis, and the other fraction freeze dried and analyzed for mass flux, carbon, nitrogen, phosphorus and silica. Data have been entered into an EPA-approved data base format.
Spring and fall food web samples have been set aside by the National Biological Service - Great Lakes Science Center (now the U.S. Geological Survey, Biological Resources Division - Great Lakes Science Center) for us to perform stable isotope analysis. We (in Saginaw Bay) and others have found stable isotopic interpretation of food webs helpful in interpreting organic contaminant bioaccumulation data.
We developed, tested and had EPA-LMMB certify a wet sample-splitter for our trap samples. Organic contaminants must be analyzed without drying the samples however dry sample mass is required for calculation of flux and for numerous other analytical procedures. A commercial trap sample-splitter is available for $35,000; we were able to adapt a dry micro-spliter for less than $1000. Samples are split in half with an accuracy and precision for mass and organic carbon of less than 1%.
FY97 Plans
- Weigh subsamples of all LMMB trap samples for Ron Rossmann (EPA-Grosse Ile) for the analysis of mercury, one of the LMMB Studys target contaminants.
- Complete LMMB project mass flux, C and N data base; deliver it to EPA and achieve certification for model applications.
- Continue as member of the LMMB Technical Coordinating Committee to advise EPA on overall program progress and synthesis.
- Attempt to retrieve the trap near the mouth of Green Bay; these samples will be the best measure that the LMMB Study has made for estimating PCB transfer from Green Bay into Lake Michigan.
Long-Term Trends in Benthic Populations
Principal Investigator: Thomas Nalepa (734-741-2285; tom.nalepa@noaa.gov) Collaborating Scientist: Steve Lozano (EPA/ERL-Duluth)
The objectives of this project are to determine trends in population abundances of benthic macroinvertebrates in selected areas of the Great Lakes and to determine the significance and reasons for any observed changes.
In FY93 this project was expanded to incorporate the requirements of EPA's Environmental Monitoring and Assessment Program (EMAP) for the Great Lakes. The goal of EMAP is to estimate the current status, trends, and changes in the Nation's ecological resources. More specifically, the program in Lake Michigan seeks to determine the areal extent of sub-nominal conditions in the nearshore zone. Status and spatial trends in the benthic community have been identified as the primary environmental indicator. Supplemental indicators include sediment toxicity (as determined by bioassay) and concentrations of organic contaminants. EMAP-related field samples were collected in Lake Michigan in both FY93 and FY94.
FY96 Progress and Accomplishments
Of the benthic samples collected in 1992 and 1993 from southern Lake Michigan, about one-half (540 samples) have been tabulated. Benthic invertebrates samples collected in July 1994 were picked, counted, identified, and the data tabulated.
Lipid concentrations in Diporeia collected from 24 sites in offshore Lake Michigan were measured. These samples were from sites visited during the Lake Michigan Mass Balance Study in fall, 1995. These additional values will supplement data collected in nearshore Lake Michigan in July, 1994.
Progress was made in determining species abundances in 148 samples from Lake Ontario and in 91 samples from Lake Superior. These samples were collected by EPA and shipped to us for identification and tabulation. These samples are part of the EMAP Great Lakes program in these two lakes.
Length/weight relationships and size frequency distributions were obtained for Diporeia collected from the 46 sites in Lake Michigan sampled in July, 1994.
The spatial differences in weight per unit length and lipid concentration of Diporeia from Lake Michigan were described. Sites were divided into three regions: north, central, and south. Both variables declined from north to south. These regional differences were likely related to differences in the quantity/quality of food sedimenting to the bottom. The spring bloom lasts longer in the north than in the south, allowing a greater supply of lipid-rich diatoms to settle to the bottom.
A data set was provided to EPA which gave abundances of all species found in 138 samples collected in Lake Michigan in July 1994. This met our obligations for one aspect of the EMAP Great Lakes Program.
FY97 Plans
- Complete compilation and file input of all benthic data collected in 1992 and 1993 from southern Lake Michigan. When completed, trends in macroinvertebrate populations between 1980-81 and 1992-93 will be assessed.
- Complete analysis of benthic macroinvertebrate samples collected in Lake Ontario (148 samples) and Lake Superior (91 samples). Data sets giving species abundances will be provided to EPA to complete our present obligations to the EMAP Great Lakes Program.
Bioavailability of Sediment-Associated Toxic Organic Contaminants
Principal Investigator: Peter Landrum (734-741-2276; peter.landrum@noaa.gov) Collaborating Scientists: Steve Wilcoxin (University of Michigan); Duane Gossiaux (GLERL)
Assessing the environmental risks associated with contaminated sediments requires determining the conditions under which sediment-associated toxic organic compounds accumulate in benthic organisms (bioaccumulation), determining whether the toxins are transferred up the food chain (biotransfer; biomagnification), and developing models for describing bioaccumulation. This work will help define the relationship between sediment characteristics and the bioavailability of organic contaminants, which in turn should improve our ability to predict the effects of contaminants associated with sediments.
FY96 Progress and Accomplishments
Data analysis was completed for a large multi-sediment investigation including investigating the character of the sediment that affects the bioavailability of non-polar organic contaminants to Diporeia spp. For the polychlorinated biphenyl (PCB) congeners, the amount of organic carbon in the sediment seemed to be the dominant factor affecting the bioavailability. However, for the polycyclic aromatic hydrocarbon (PAH) congeners, the polarity of the organic matter was most dominant with the more non-polar organic matter yielding the highest bioavailability. This finding is contrary to the expected behavior that the more non-polar the organic matter the lower would be the bioavailability.
Products
Kukkonen, J. and P.F. LANDRUM. 1996 Distribution of organic carbon and organic xenobiotics among different particle-size fractions in sediments. Chemosphere 32:1063-1076
Mulsow, S.G. and P.F. LANDRUM. 1995. Bioaccumulation of DDT in a marine polychaete, the Conveyor-belt deposit feeder Heteromastus filiformis (Claparede) Chemosphere 31:3141-3152.
FY97 Plans
- Demonstrate that factors other than sediment organic carbon content are primarily responsible for the bioavailability of organic contaminants by Diporeia spp.
- Review and summarize the role of lipid content on the bioaccumulation and toxicity of environmental contaminants in aquatic organisms.
- Develop new research focus on bioavailability of sediment-associated contaminants in light of past findings.
Trophic transfer of atmospheric and sedimentary contaminants into Great Lakes fish: controls on ecosystem scale response times
Principal Investigator: Brian Eadie (734-741-2281; brian.eadie@noaa.gov) Collaborating Scientists: Joel Baker (University of Maryland); Nathanial Ostrum, Peggy Ostrum, Donald Hall (Michigan State University); Douglas Lee (University of Connecticutt).
During the past two decades, inventories of persistent, bioaccumulative organic contaminants have decreased dramatically in the Great Lakes ecosystem. Initial rates of decline of PCBs in the Great Lakes were rapid during the 1970's and early 1980's, but, unfortunately, this rate of decline has apparently slowed since the second half of the 1980s. The most recent data show little or no change in PCB levels in the Great Lakes fishery. This apparent stabilization of PCB levels near the Food and Drug Administration (FDA) advisory level is problematic. The persistence of PCBs in Great Lakes fish has led some to the call for additional regulations, but others argue that the decrease in the rate of recovery of PCBs in the Great Lakes is a natural consequence of internal recycling and continental scale atmospheric exchange and that further regulations are neither cost-effective or warranted.
This project will conduct a field study in Grand Traverse Bay, Lake Michigan to quantify trophic transfer of PCBs through the northern Great Lakes food web, with emphasis on the heretofore unstudied linkage between atmospheric contaminant inputs and benthic food webs via rapidly-settling particles. A quantitative, process-driven model of contaminant transfer in the Great Lakes food web will be developed that distinguishes between `new' (i.e., regional atmospheric deposition) and `in-place' (i.e., recycling from contaminated sediments) sources of contaminants that support the slowly-changing contaminant inventories in the highest trophic levels of the Great Lakes.
Our objectives are to quantify the absolute and relative magnitudes of PCB transfers into the northern Great Lakes fisheries from three exposure routes: (1) atmospheric deposition transferred through the pelagic food web, (2) atmospheric deposition transferred via rapidly-settling particles, trough the benthic food web, and; (3) transfer from historically-contaminated, in-place sediments through the benthic food web. We hypothesize that each of these routes differ both in their efficiencies of contaminant transfer and in their characteristic response times.
FY96 Progress and Accomplishments
None - this is a new project starting in FY97.
FY97 Plans
- Deploy, retrieve, and redeploy two arrays of sequencing sediment traps in Grand Traverse Bay to sample settling fluxes of PCB and other contaminants
- Process and distribute samples to collaborators for constituent analyses.
Last updated: July 10, 2002 mbl