CURRICULUM VITAE
GERHARDT F. RIEDEL

Research Biogeochemist
Smithsonian Institution
Smithsonian Environmental Research Center
PO Box 28, 647 Contees Wharf Road
Edgewater, MD 21037

443-482-2499 (V)
443-482-2380 (F)

riedelf@si.edu

EDUCATION
1983 Ph.D., Biological Oceanography, Oregon State University 
1978 M.S., Biological Oceanography, Oregon State University
1974 A.B., Biology, Humboldt State University 
1974

B.S., Oceanography, Humboldt State University  

PROFESSIONAL EXPERIENCE

2004-Present  Research Biogeochemist, Smithsonian Institution, Smithsonian Environmental Research Center.
1999-2004

Associate Curator, The Academy of Natural Sciences, Estuarine Research Center.

1993-1999    Assistant Curator, The Academy of Natural Sciences, Benedict Estuarine Research Center.
1987-1993

Senior Scientist, The Academy of Natural Sciences, Benedict Estuarine Research Laboratory.

1985-1987 Postdoctoral Investigator, The Academy of Natural Sciences, Benedict Estuarine Research Laboratory.
1983-1985 Postdoctoral Fellow, Harbor Branch Foundation.
1977-1983 Graduate Research and Teaching Assistant, Oregon State University.
1974-1977 Graduate Research Assistant, Oregon State University.

RESEARCH INTERESTS

Trace metal and nutrient geochemistry and biogeochemistry, particularly the influence of organisms on the speciation of trace elements, and the flux of trace elements across the sediment/water interface.  Trace element and nutrient uptake and incorporation by aquatic organisms, with emphasis on uptake by phytoplankton and food chain transfer.

HONORS and AWARDS
2002

Appointed to Editorial Board, 2002-2004, Marine Ecology Progress Series

Appointed to Editorial Board, 2002-2004, Environmental Toxicology and Chemistry.

2001

Session Co-Chair, Fate and Transfer of Arsenic in the Environment, 22 nd Annual SETAC Meeting, Washington, D.C. November 11-14, Baltimore Convention Center, Baltimore, Maryland.

Invited Poster - Bioaccumulation of Arsenic in Southeast Coastal and Chesapeake Bay Oysters. 22 nd Annual SETAC Meeting, Washington, D.C. November 11-14, Baltimore Convention Center, Baltimore, Maryland.

Invited Speaker - Arsenic in Chesapeake Bay Tributaries. Arsenic in the Environment, U.S. Geological Survey Workshop, February 21-22, Denver, Colorado.

1999

Invited Speaker- The Effects of Stormwater Runoff on the Anacostia River, America's Archetypical Urban River: The influence of storm events on trace element concentrations. Session on Estuarine Biogeochemistry of Chemical Contaminants, Society of Environmental Toxicology and Chemistry 20 th Annual meeting, November 14-18, Philadelphia, PA.

Invited Speaker - The Effect of Metals in the Pocomoke Ecosystem, Harmful Algal Blooms Technical Advisory Committee, Salisbury State University, Aug. 19, 1999.

Invited Participant - Chesapeake Bay Programs Toxic ' s Non-Point Source Forum, Metropolitan Washington Council of Governments Training Center, Washington D.C., Aug. 17, 1999.

1998

Invited Speaker - Virginia-Maryland Natural Resources Colloquium, Stratford Hall Plantation, Virginia, Aug 12, 1998

Invited Speaker - Chesapeake Bay Mass Balance Workshop, Solomons, MD, May 7-8, 1998

1997

Invited Speaker, Understanding Selenium in the Aquatic Environment, Salt Lake City, Utah. March 6-7, 1997

1996

Session Co-Chair, 17'th Annual SETAC Meeting, Washington, D.C. November 17-21, 1996.

1995

Chairman, Toxic Data Compilation Meeting for the Patuxent River and Upper Chesapeake Bay. U.S. EPA, Annapolis MD.

Invited Poster, Society of Toxicology and Chemistry, Sixth World Conference, Vancouver, B.C. Canada. Nov. 5-9 1995.

1994

Session Co-Chair, International Association for Great lake Research and Estuarine Research Federation 37'th conference, Windsor, Ontario, Canada. June 5-9, 1994.

Session Chair, Ocean Sciences Meeting, American Geophysical Union, San Diego, CA. Feb 21-25, 1994.

1991

Invited Speaker, International Estuarine Research Conference, San Francisco, Calif.

Award for Creativity in Project Design, Academy of Natural Sciences, Division of Environmental Research.

1990 "Above and Beyond Award", Academy of Natural Sciences, Division of Environmental Research.
1988

Plenary Speaker, "Understanding the Estuary: Advances in Chesapeake Bay Research", Chesapeake Research Consortium, Baltimore, Maryland.

1987

Award for Contributions to Laboratory Operations, Academy of Natural Sciences, Division of Environmental Research.

1983 Postdoctoral Fellowship, Harbor Branch Institution
1980 Nominated to Membership in Sigma Xi, the Scientific Research Society
1974

Graduated Magna Cum Laude, Humboldt State University, B.S. Oceanography, A.B. Biology


PUBLICATIONS
2006

Riedel, GF. Ecotoxicology: Copper In: Encyclopedia of Ecology, Elsevier, submitted.

Breitburg, D. L. and Riedel G. F. Multiple Stressors in Marine Systems. 2004. Chapter 10 In: L. E. Crowder (ed.) Marine Conservation Biology: The Science of Maintaining the Sea ' s Biodiversity (MCB). Island Press.

2003

Riedel, G. F. and J. G. Sanders. The interrelationships between eutrophication, trace element cycling, and trophic complexity in estuaries: A mesocosm study. Estuaries 26: 339-351.

Riedel, G. F., J. G. Sanders and D. L. Breitburg. Seasonal variability in response of estuarine phytoplankton communities to stress: Linkages between toxic trace elements and nutrient enrichment. Estuaries 26:323-338.

2002

Riedel, G. F. and N. Valette-Silver. Bioaccumulation of arsenic in oysters from southeast coastal U.S. and Chesapeake Bay: seasonal and genetic factors. Chemosphere 49(1): 27-37.

2000

Riedel, G. F., S. A. Williams, G. S. Riedel, C. C. Gilmour and J. G. Sanders. Temporal and Spatial Patterns of Trace Elements in the Patuxent River: A Whole Watershed Approach. Estuaries 23: 521-535.

Abbe, G. R., G. F. Riedel and J. G. Sanders. Factors that Influence the Accumulation of copper and Cadmium by transplanted Eastern Oysters (Crassostrea Virginica) in the Patuxent River, Maryland. Marine Environmental Research 49:377-396.

1999

Valette-Silver, N. J., G. F. Riedel, E. A. Crecelius, H. Windom, R. G. Smith and S. S. Dolvin. Elevated arsenic concentrations in bivalves from the southeast coasts of the USA. Marine Environmental Research 48:311-333.

Breitburg, D. L., J. G. Sanders, C. C. Gilmour, C. A. Hatfield, R. W. Osman, G. F. Riedel, S. P. Seitzinger and K. P. Sellner. Variability in responses to nutrients and trace elements, and transmission of stressor effects through an estuarine food web. Limnology and Oceanography 44: 837-86 .

Riedel, G. F., J. G. Sanders and R. W. Osman. Biogeochemical Control on the Flux of Trace Elements from Estuarine Sediments: Effects of Seasonal and Short-term Anoxia. Marine Environmental Research 47:349-372.

1998

Riedel, G. F., G. R. Abbe and J. G. Sanders. Trace Metals Concentrations in Oysters from the Patuxent River, Maryland: Temporal and Spatial Variation. Estuaries 21: 423-434.

Sanders, J. G. and G. F. Riedel. Metal accumulation and impacts in phytoplankton. pp 59-76 in: W. Langston and M. Bebianno (eds.) Metal Metabolism in Aquatic Environments. Chapman and Hall, London.

Riedel, G. F and J. G. Sanders. Trace Element Speciation and Behavior in the Tidal Delaware River. Estuaries 21:78-90.

Benoit, J. M., C. C. Gilmour, R. P. Mason, G. S. Riedel, G. F. Riedel, and K. A. Sullivan. Sources and cycling of mercury in the Patuxent Estuary. Biogeochemistry 40:249-265.

1997

Riedel, G. F., J. G. Sanders and R. W. Osman. Biogeochemical control on the flux of trace elements from estuarine sediments: Water column oxygen and benthic infauna. Estuarine Coastal and Shelf Science 44:23-38.

1996

Riedel, G. F., J. G. Sanders, and C. C. Gilmour. Uptake, transformation and impact of Selenium in freshwater phytoplankton and microbial communities:. Aquatic Microbial Ecology 11:43-51.

Riedel, G. F and J. G. Sanders. The Influence of pH and Media Composition on the Uptake of Inorganic Selenium by Chlamydomonas reinhardtii. Environmental Toxicology and Chemistry 15:1577-1583.

Bowie, G. L., J. G. Sanders, G. F. Riedel, C. C. Gilmour, D. L. Breitburg, G. A. Cutter and D. B Porcella. 1996. Assessing selenium cycling and accumulation in aquatic ecosystems. Water Air and Soil Pollution 90:93-104
1996 Riedel, G .F., G. R. Abbe, and J. G. Sanders. Silver and copper accumulation in two estuarine bivalves, the eastern oyster (Crassostrea virginica) and the Hooked Mussel (Ischadium recurvum). Estuaries 18:445-455.
1994

Abbe, G. R., J. G. Sanders, and G. F. Riedel. Silver uptake by the oyster (Crassostrea virginica): Effect of organism size and storage sites. Estuarine Coastal and Shelf Science 39:249-260.

Sanders, J. G., G. F. Riedel and R. W. Osman. Arsenic Cycling and Impact in Estuarine and Coastal Marine Ecosystems. J. Nriagu (ed.) "Advances in Environmental Science and Technology: Arsenic in the Environment," John Wiley and Sons, New York, pp. 289-308.

Riedel, G.F., J.G. Sanders, and R.W. Osman. 1994. The influence of fluctuating oxygen on the flux of As, Cd, Cu and Mn from contaminated Chesapeake Bay sediments. Transactions of the American Geophysical Union 75(3):144.

1993

Riedel, G. F. The annual cycle of arsenic in a temperate estuary. Estuaries 16: 533-540.

Sanders, J. G. and G. F. Riedel. Trace element transformation during the development of an estuarine algal bloom. Estuaries 16: 521-531.
1992 Sanders, J. G. and G. F. Riedel. Sources, cycling and fate of contaminants in Chesapeake Bay. Water Science and Technology. 26:2645-2652.
1991

Riedel, G. F., D. P. Ferrier, and J. G. Sanders. Uptake of selenium by freshwater phytoplankton. Water Air and Soil Pollution 57-58:23-30.

Connell, D. B., J. G. Sanders, G. F. Riedel, and G. R. Abbe. Pathways of silver uptake and trophic transfer in estuarine organisms. Environmental Science and Technology 25:921-924.

Sanders, J. G., G. F. Riedel, and G. R. Abbe. Factors controlling the spatial and temporal variability of trace metal concentrations in Crassostrea virginica (Gmelin). Pages 335-339 in M. Elliott and J. P. Ducrotoy (eds.) Estuaries and Coasts: Spatial and Temporal Intercomparisons. Olsen & Olsen, Helstedsvej.

Sanders, J. G., G. F. Riedel, and D. P. Ferrier. 1991. Changes in community structure of Chesapeake Bay phytoplankton when exposed to low levels of trace metals: Management implications. Pages 451-460 in J. A.

Mihursky and A. Chaney (eds.) New Perspectives in the Chesapeake System: A Research and Management Partnership. Proceedings of a Conference 4-6 December 1990, Baltimore MD. Chesapeake Research Consortium Publication No. 137 1990.

1990 Sanders, J. G., G. R. Abbe, and G. F. Riedel. Silver uptake and subsequent effects on growth and species composition in an estuarine community. Sci. Tot. Environ. 97:761-769.
1989

Sanders, J.G., R.W. Osman and G.F. Riedel. Pathways of arsenic uptake and incorporation in estuarine phytoplankton and the filter-feeding invertebrates, Eurytemora affinis , Balanus improvisus , and Crassostrea virginica . Mar. Biol. 103:319-325.

Riedel, G. F., J. G. Sanders, and R. W. Osman. The role of three species of benthic invertebrates in the transport of arsenic from contaminated estuarine sediments. Journal of Experimental Marine Biology and Ecology 134:143-155.

1988

Riedel, G. F. Interspecific and geographic variation of the chromium sensitivity of algae. Pages 537-548 in G. W. Suter and M. Lewis (eds.), Proceedings, 11th Symposium on Aquatic Toxicology and Hazard Assessment. American Society of Testing and Materials.

Riedel, G. F. and J. G. Sanders. Factors affecting the bioavailability of toxic trace elements to estuarine organisms. Pages 14-25 in M.P. Lynch and E.C. Krome (eds.) Understanding the Estuary: Advances in Chesapeake Bay Research. Chesapeake Research Consortium Publication 129.

Sanders, J. G. and G. F. Riedel. Chemical and physical processes influencing bioavailability of toxics in estuaries. Pages 87-106 in M. P. Lynch and E. C. Krome (eds.), Perspectives on the Chesapeake Bay. Recent Advances in Estuarine Sciences. Chesapeake Research Consortium, Publication 127.

Sanders, J. G. and G. F. Riedel. The use of enclosed ecosystems for the study of cycling and impact of trace elements. Pages 23-28 in Proceedings of the Oceans '88 Conference. IEEE, Publication CH2585 8/88.

1987

Sanders, J. G. and G. F. Riedel. Control of trace element toxicity by phytoplankton. Pages 131-149 in J. A. Sanders, L. Kosak-Channing and E. E. Conn (eds.), Recent Advances in Phytochemistry, Vol. 21.

Riedel, G. F., J. G. Sanders, and R. W. Osman. The effect of biological and physical disturbances on the transport of arsenic from contaminated sediments. Estuarine Coastal and Shelf Science 25:693-706.

1985

Riedel, G. F. Photoreduction of Cr(VI) in natural waters. Transactions of the American Geophyical Union 66:1257.

Riedel, G. F. The relationship between chromium(VI) uptake, sulfate uptake and chromium(VI) toxicity to the estuarine diatom Thalassiosira pseudonana . Aquatic Toxicolgy 7:191-204.

Riedel, G. F. and D. M. Nelson. Uptake of silicon by algae with no known Si requirement . II. Strong pH dependence of uptake parameters in Phaeodactylum tricornutum (Bacillariophyceae). Journal of Phycology 21:168,171.

1984

Nelson, D. M., G. F. Riedel, J. R. Lara,Lara and R. Millam,Nunez. Uptake of silicon by algae with no known Si requirement. I. True cellular uptake and pH-induced precipitation by Phaeodactylum tricornutum (Bacillariophyceae) and Platymonas sp. (Prasinophyceae). Journal of Phycology. 20:141-147.

Riedel, G. F. The influence of salinity and sulfate on the toxicity of chromium(VI) to the estuarine diatom Thalassiosira pseudonana . Journal of Phycology 20:496-500.

Riedel, G. F., S. Wilson, and R. L. Holton. Trace metals in the Columbia River estuary following the 18 May 1980 eruption of Mount St. Helens. Pacific Science 38:340-349.

1983 Frey, B. E., G. F. Riedel, B. Bass, and L. F. Small. Sensitivity of estuarine phytoplankton to hexavalent chromium. Estuarine Coastal and Shelf Science 17:181-188.

PRESENTATIONS
2004

Riedel, G.F., D.J. Velinsky, J Ashley, T.L. Wade and J. Cornwell. Sediment Contamination in the Anacostia River: A Pollution History of Washington, D.C. Society of Environmental Toxicology and Chemistry, Fourth SETAC World Congress, 14-18 Nov., 2004, Portland, OR.

Velinsky, D.J., G.F. Riedel, J.T. Ashley, G.D. Forster and C. Schultz. Spatial and Temporal Changes in Trace Contaminants in the Tidal Anacostia River after Precipitation Events. Society of Environmental Toxicology and Chemistry, Fourth SETAC World Congress, 14-18 Nov., 2004. Portland, OR.

Hancock, T.C., J.M. Denver, C.V. Miller J.R. Gabarino, R.L. Wershaw, D.W Rutherford, R.S. Oremland, A.L. foster, M. Schreiber, G.F. Riedel, J.F. Stoltz. Arsenic in the Environment from the Land Spreading of Poultry Waste: Summary of Recent Findings. Regional Science Workshop on Animal Feeding Operations (AFOs), Dec. 6-9, 2004, University of Maryland, College Park, MD.

Riedel, G.F. Arsenic speciation as an Indicator for Estuarine Phosphate Limitation. 8 th International Estuarine Biogeochemistry Symposium. May 16-20, 2004. Chesapeake Biological Laboratory, Solomons, Maryland.

2003 Riedel, G.F. Trace Element Studies in the Patuxent River, Maryland. Dec. 3, Smithsonian Environmental Research Center, Shady Side, Maryland.
2002 Riedel, G.F. and C. C. Gilmour and J. G. Sanders. Estuarine Eutrophication and Trace Element Cycling: Cadmium in the Patuxent River as an example. COASTES Final Workshop. Sept. 18, Smithsonian Environmental Research Center, Shady Side, Maryland.
2001

Riedel, G. F. and Nathalie Valette-Silver - Bioaccumulation of Arsenic in Southeast Coastal and Chesapeake Bay Oysters. Poster presentation at 22 nd Annual SETAC Meeting, Washington, D.C. November 12, Baltimore Convention Center, Baltimore, Maryland.

Riedel, G.F. An Introduction to the Academy of Natural Sciences ' Estuarine Rearch Center. Coastal Conservation Association, Southern Maryland Chapter, Hughesville, Maryland.

Riedel, G.F. Current Concepts in Sediment Toxicity. Environmental Associates, March 29. Academy of Natural Science, Philadelphia, Pennsylvania.

Riedel, G. F. Environmental Health Studies at Eagle Harbor, Maryland. Eagle Harbor City Council Meeting, March 3 Eagle Harbor, Maryland.

Riedel, G. F. Trace Elements in the Patuxent River Watershed: The Canary in the Coal Mine or the Boy Who Cried Wolf? Old Dominion University, Department of Ocean, Earth, and Atmospheric Sciences, March 1, Norfolk, Virginia.

Riedel, G. F. Arsenic in Chesapeake Bay Tributaries. Arsenic in the Environment, U.S. Geological Survey Workshop, February 21-22, Denver, Colorado.

2000 Riedel, G. F., J. G. Sanders and D. L. Breitburg. Seasonal Differences in the Response of Estuarine Phytoplankton to Individual Trace Elements, Trace Element Mixtures, and Nutrients Loads. AGU/ASLO Ocean Sciences 2000 Meeting,, January 24-28, 2000, Austin, Texas.
1999

Riedel, G.F., D.J. Velinsky, S.A. Williams, A. Wilson-Finelli. The Effects of Stormwater Runoff on the Anacostia River, America's Archetypical Urban River: The influence of storm events on trace element concentrations. Society of Environmental Toxicology and Chemistry 20 th Annual meeting, November 14-18, Philadelphia, PA.

Riedel, G. F, C. C. Gilmour, S. A. Williams, G. S. Riedel. The Sources of Trace Elements to The Patuxent River Estuary. Society of Environmental Toxicology and Chemistry 20 th Annual meeting, November 14-18, Philadelphia, PA.

Riedel, G. F., J. G. Sanders and D. L. Breitburg. The role of individual trace elements, trace element mixtures, and nutrients in the inhibition of phytoplankton in the Patuxent River Estuary. Estuarine Research Federation Meeting, New Orleans, Sept.25-30, 1999

Riedel, G.F and J.G. Sanders. Metals in the Chesapeake Bay Ecosystem and its Effect on Phytoplankton Production. The Effect of Metals in the Pocomoke Ecosystem, Harmful Algal Blooms Technical Advisory Committee, Salisbury State University, Aug. 19, 1999.

Riedel, G.F. G. S. Riedel and C. C. Gilmour. Regional and Temporal Variations in the Sources of Trace Elements to the Patuxent River Estuary. American Society of Limnology and Oceanography, Feb. 1-5, 1999, Santa Fe, New Mexico.

1998

Riedel, G.F., Sanders J.G., and Breitburg, D.L. The Effects of Multiple Stressors on Estuarine Ecosystems: The Influences of Nutrient Enrichment on Trace Element Cycling. Society of Toxicology and Chemistry Meeting, Nov. 15-20, Charlotte, North Carolina.

Riedel, G. F. Toxic Substances in Chesapeake Bay, Virginia-Maryland Natural Resources Colloquium, Aug 12, 1998, Stratford Hall Plantation, Virginia.

Riedel, G.F. Benthic Fluxes of Trace elements in Chesapeake Bay. Chesapeake Bay Mass Balance Workshop, May 7-8, Solomons, Maryland.

1997

Riedel, G.F. Flux of trace elements from Chesapeake Bay sediment, and the effect on lower trophic levels. G.F. Riedel and J.G. Sanders . Poster presentation at Estuarine Research Federation Meeting, October 12-16, Providence, Rhode Island.

Riedel, G.F., S. A. Williams, G. S. Riedel and C. C. Gilmour. The Relationship Between Urbanization and Trace Elements in a Chesapeake Bay Watershed: the Patuxent River Maryland. Poster presentation. American Geophysical Union meeting, May 19-24, Baltimore, MD.

Riedel, G. F., J. G. Sanders, C. C. Gilmour, C. E. Goulden, D. L. Breitburg and R. W. Osman. Se Interactions in Aquatic Ecosystems and Effects on Fish Populations. Presented at Understanding Selenium in the Aquatic Environment: Kennecott Selenium Symposium, March 6-7,1997, Salt Lake City, Utah.

Riedel, G.F., S.A. Williams, G.S. Riedel and C.C. Gilmour Trace Elements in the Patuxent River. Presented at COASTES Review meeting, Jefferson Patterson Park, St. Leonard, Maryland, Feb. 3-4, 1997

1996

Riedel, G.F. S. Williams, G.S. Riedel and C.C. Gilmour. Trace Elements in the Patuxent River. Presented at Watershed Symposium: Runoff and Retention, 17'th Annual SETAC Meeting, Washington, D.C.

Riedel, G. F. S. Williams, G. S. Riedel and C. C. Gilmour. Trace Elements in the Patuxent River. Presented at session on Contaminants, ECSA 26 and ERF 96 Symposium, Middelburg, The Netherlands.

1995

Riedel, G.F, J.G. Sanders and G. R. Abbe. High Concentrations of Trace Metals in Oysters from the Patuxent River, Maryland. Presented at SETAC Second World Congress, Poster Session on Temporal Trends in Contamination, Nov. 9, 1995, Vancouver, B.C., Canada.

Riedel, G. F. Trace element concentrations in the Patuxent River. Presented at the Toxics Data Compilation Meeting on the Patuxent River and Upper Chesapeake Bay. Dec 15, 1995, Annapolis, Maryland.
1994

Riedel, G. F., J. G. Sanders & R. W. Osman The Influence of Fluctuating Oxygen on the Flux of As, Cd, Cu and Mn from Contaminated Chesapeake Bay Sediments. Joint American Geophysical Union-American Society of Limnology and Oceanography Ocean Sciences meeting, February 21-25, 1994, San Diego, California.

Riedel, G. F., J. G. Sanders and C. C. Gilmour. A Microcosm Study of Interactions between Sediment, Water and Biota in Chesapeake Bay. Chesapeake Research Conference, Norfolk Virginia, June 1-3, 1994.

Riedel, G. F., J. G. Sanders and R. W. Osman. The Influence of Water Column Oxygen Concentrations and Benthic Infauna on the Flux of Trace Elements from Contaminated Estuarine Sediments. Joint Estuarine Research Federation/International Association of Great Lakes Research meeting, Windsor, Ontario, Canada, June 5-9, 1994.

1993 Riedel, G. F. Dissolved trace elements in Chesapeake Bay - A review. United States Environmental Protection Agency, Chesapeake Bay Critical Issues Forum, April 14, 1993, Annapolis, Maryland
1992

Riedel, G. F., J. G. Sanders and R. W. Osman The effects of fluctuating oxygen concentrations and biota on the flux of trace elements from Chesapeake Bay sediments. Joint ECSA-Estuarine Research Federation Meetings, September 13-18, Plymouth, England.

Riedel, G. F., J. G. Sanders and R. W. Osman. The effects of fluctuating oxygen concentrations and biota on the flux of trace elements from Chesapeake Bay sediments. Chesapeake Bay Toxic Studies Workshop, February 19-20, Virginia Institute of Marine Sciences, Gloucester, Virginia.

Riedel, G. F. Trace element speciation and behavior in the tidal Delaware River. Delaware Estuary Program Scientific and Technical Advisory Committee, Nov.5, 1992, Philadelphia, Pennsylvania.

Riedel, G. F. Selenium cycling and impact in aquatic systems. Progress report for 1990-1991 on phytoplankton, analytical and zooplankton sections at annual review meeting for Electric Power Research Institute, June 1992, Raleigh, North Carolina.

1991 Riedel, G. F. , J. Sanders and R. Osman. Factors affecting arsenic cycling and geochemistry in Chesapeake Bay: The influence of intermittent anoxia and biota on flux from sediment. 11th International Estuarine Research Conference, November 10-14, 1994, San Francisco, California.
1990

Riedel, G. F. and D. Ferrier. Uptake of selenium by freshwater phytoplankton. International Conference on Metals in Soils, Water, Plants and Animals, Orlando, FL, April 30 - May 3, 1990.

Riedel, G. F., G. Abbe and J. G. Sanders Trace element concentrations in bivalves transplanted to the upper Patuxent River Estuary, Maryland. Annual Meeting of the American Society of Limnology and Oceanography, Williamsburg, Virginia, June 10-15, 1990.
1988

Riedel, G. F and J. G. Sanders . Use of enclosed ecosystems for the study of cycling and impact of trace elements. Oceans 88, Baltimore, Maryland, Nov. 1-2, 1988.

Riedel, G. F. and J. G. Sanders. Modification of trace element speciation by phytoplankton. Atlantic Estuarine Research Society, Oct. 29-30, 1988. Solomons, Maryland.

Riedel, G. F. and J. G. Sanders. Modification of trace element toxicity by estuarine phytoplankton. International Symposium on the Fate and Effects of Toxic Chemicals in Large River and Estuaries, Oct. 10-14, 1988, Quebec, Canada.

Riedel, G. F. and J. G. Sanders. Factors affecting bioavailability of toxic trace elements to estuarine organisms. "Understanding the Estuary: Advances in Chesapeake Bay Research." Chesapeake Research Consortium, March 29-30, 198, Baltimore, Maryland.

Riedel, G. F., J. G. Sanders and R. W. Osman. Control of arsenic distribution and flux in estuarine sediments by benthic organisms. Annual Meeting of American Geophysical Union, Jan. 18-22, 1988, New Orleans, Louisiana.

1987

Riedel, G. F. Interspecific and geographic variation of chromium sensitivity of algae. 11th Symposium on Aquatic Toxicology and Hazard Assessment. Poster Session. American Society of Testing and Materials, May 10-12, 1987, Cincinnati, Ohio.

Riedel, G. F., J. G. Sanders and R. W. Osman. The role of benthic invertebrates in the flux of arsenic between sediments and the water column, Environmental risk: Recognition, assessment and management. 8th Annual Meeting, Society of Environmental Toxicology and Chemistry, Nov. 9-12, 1987, Pensacola, Florida.

1986

Riedel, G. F. Photoreduction of hexavalent chromium in natural waters. Winter meeting, American Geophysical Union, January 13-17, 1986, New Orleans, Louisiana.

Riedel, G. F. The environmental chemistry of chromium(VI). The University of Maryland, October 3, 1986, College Park, Maryland.

Riedel, G. F. The sensitivity of algae to chromium(VI). The American Society of Limnology and Oceanography/American Phycological Society meeting, June 22-26, 1986, University of Rhode Island, Providence, Rhode Island.

1985 Riedel, G. F. The biogeochemistry of chromium. The Academy of Natural Sciences, Nov. 3, 1985, Philadelphia, Pennsylvania.
1984

Riedel, G. F. The salinity dependence of Cr(VI) toxicity to Thalassiosira pseudonana : competitivity with sulfate. Joint American Geophysical Union-American Society of Limnology and Oceanography Ocean Sciences meeting, Jan. 23, 1984, New Orleans, Louisiana.

Riedel, G. F. Chromium(VI) effects on algae: regulation by sulfate ion concentration. The Sixth Southeastern Phycological Colloquy, Florida Institute of Technology, Oct. 18-19, 1984, Melbourne, Florida.

Riedel, G. F. Chromium(VI) uptake by Thalassiosira pseudonana : Competition for uptake with sulfate ion. Winter Meeting of the American Society of Limnology and Oceanography, Dec. 3-7, 1984, San Francisco, California.

1981 Riedel, G. F. , S. Wilson and R. Holton Trace metals in the Columbia River Estuary following the May 18, 1980 eruption of Mt. St. Helens. Estuarine Research Federation, Nov. 6, 1981, Glendenen Beach, Oregon.
1980

Riedel, G. F., D. M. Nelson, J. R. Lara-Lara and R. Millam-Nunez Uptake and release of silicic acid by the diatom Phaeodactylum tricornutum and the green algae Platymonas sp. The American Society of Limnology and Oceanography, 27 Dec. 1980, Seattle, Washington.

AFFILIATIONS

American Association for the Advancement of Science

American Geophysical Union

American Society of Limnology and Oceanography

Estuarine Research Federation

Phycological Society of America

Sigma Xi

Society of Environmental Toxicology and Chemistry