Large Lakes Observatory

Biogeochemistry and Geochemistry

• Anoxia and Black Shales
   
• Carbon Isotope Biogeochemistry
   
• Geochemistry of cosmogenic nuclides
   
• Microbial Biogeochemistry
   
• Natural Organic Matter Structure and Reactivity
   
• Organic Sulfur Formation and Sedimentary Sulfur Cycling
   
• Photoreactivity of Riverine and Estuarine Organic Matter
   
• Trace metal and nutrient biogeochemistry

Anoxia and Black Shales

The factors controlling the formation of organic rich sedimentary deposits are debated, but include primary production, sedimentary decomposition, and bulk sedimentation and dilution. Among the factors involved in sedimentary decomposition, anoxia and related microbial activity have received significant attention. We are investigating these processes in modern environments such as the Cariaco and Orca Basins, and applying our understanding of these environments to reconstruct the factors controlling the deposition of ancient organic rich black shales (Devonian Appalachian Basin, New York) such as have occurred widespread at times in Earth's history. Collaborators include B. Sageman (Northwestern University), T. Lyons (MU), and D. Hollander (USF).

Publications:

Lyons, T.W., J.P. Werne, and D.J. Hollander, R.W. Murray, 2003. Contrasting sulfur geochemistry and Fe/Al and Mo/Al ratios across the last oxic-to-anoxic transition in the Cariaco Basin, Venezuela. Chemical Geology. v. 195, p. 131-157.

Sageman, B.B., A.E. Murphy, J.P. Werne, C.A. Ver Straeten, D.J. Hollander, and T.W. Lyons, 2003. A tale of shales: the relative roles of production, decomposition, and dilution in the accumulation of organic-rich strata, Middle-Upper Devonian, Appalachian basin. Chemical Geology, v. 195, p. 229-273.

Werne, J.P., B.B. Sageman, T.W. Lyons, and D.J. Hollander, 2002. An integrated assessment of a "type euxinic" deposit: Evidence for multiple controls on black shale deposition in the middle Devonian Oatka Creek Formation. American Journal of Science, v. 302, pp. 110-143.

Back to top

Carbon Isotope Biogeochemistry

Carbon isotopes, particularly of individual organic compounds traceable to a known biological source, are extremely useful for understanding a variety of biogeochemical processes and environmental conditions. Our studies focus on the factors controlling carbon isotope fractionation by autotrophs, primarily photosynthesizers, and how we can utilize carbon isotope data for reconstructing environmental processes and changes. Work has been carried out in the Cariaco Basin, Venezuela (with collaborator D. Hollander at Univ. South Florida, USF), and projects are being initiated in Lake Superior and Crater Lake, Oregon.

Publications:

Werne, J.P. and D.J. Hollander (2004) Balancing supply and demand: Controls on carbon isotope fractionation in the Cariaco Basin (Venezuela) Younger Dryas to Present. Marine Chemistry. v. 92, no. 1-4, pp. 275-293.

Back to top

Geochemistry of cosmogenic nuclides

In situ -produced cosmogenic nuclides are used for quantification of rates and timing of geomorphological processes. Detailed knowledge of the production systematics of cosmogenic nuclides is required for rigorous interpretation of their distributions in near-surface rocks.

Publications:

R. Braucher E.T. Brown, D.L. Bourlès and F. Colin, 2003. In situ produced 10 Be measurements at great depths: Implications for production rates by fast muons, Earth and Planetary Science Letters, 211, 251-258.

E.T. Brown, T.W. Trull, P. Jean-Baptiste, G.M. Raisbeck, D.L. Bourlès, F. Yiou, and B. Marty, 2000. Determination of cosmogenic production rates of 10 Be, 3 He, and 3 H in water, Nuclear Instruments and Methods in Physics Research B, 172, 876-886.

T.W. Trull, E.T. Brown, B. Marty, G.M. Raisbeck, and F. Yiou, 1995. Accumulation of cosmogenic 10 Be and 3 He in quartz from Pleistocene beach terraces in Death Valley: Implications for cosmic ray exposure dating of young surfaces in hot climates, Chemical Geology 119, 191-207.

E.T. Brown, D.L.Bourlès, F. Colin, G.M. Raisbeck, F. Yiou and S. Desgarceaux, 1995. Evidence for muon-induced in situ production of 10 Be in near-surface rocks from the Congo, Geophysical Research Letters 22, 703-706.

Back to top

Microbial Biogeochemistry

Microbes control the vast majority of biogeochemical processes in sedimentary and aqueous environments, but identifying the critical organisms, the chemical signals they leave in aquatic systems, and linking the structure of microbial communities to the biogeochemical processes they perform is difficult. We are involved in a number of studies combining molecular isotopic studies with microbiology to try to understand the impact of microbes on natural systems. Work has been carried out in eastern Mediterranean mud volcanoes on the molecular isotopic signature of the anaerobic oxidation of methane (with collaborators J. Sinninghe Damsté from the Royal Netherlands Institute for Sea Research (NIOZ) and others), and studies are being initiated in Crater Lake, Oregon on the microbial biogeochemistry of green nonsulfur bacteria and crenarchaeota (with collaborators E. Urbach and H. Simon from Univ. Wisconsin).

Publications:

Werne, J.P., and J.S Sinninghe Damsté (2005) Mixed sources contribute to the molecular isotopic signature of methane-rich mud breccia sediments of Kazan mud volcano (Eastern Mediterranean). Organic geochemistry, v. 36, no. 1, pp. 13-27.

Werne, J.P., T. Zitter, R.R. Haese, G. Aloisi, I. Bouloubassi, S. Heijs, A. Fiala-Medioni, R.D. Pancost, J.S. Sinninghe Damsté, G. de Lange, L.J. Forney, J.C. Gottschal, J.-P. Foucher, J. Mascle, J. Woodside, and the MEDINAUT and MEDINETH Shipboard Scientific Parties. 2004. Life at cold seeps: A synthesis of ecological and biogeochemical data from Kazan mud volcano, eastern Mediterranean Sea. Chemical Geology, v. 205, no. 3-4, p. 367-390.

Werne, J.P., M. Baas, J.S. Sinninghe Damsté, 2002. Molecular isotopic tracing of carbon flow and trophic relationships in a methane-supported microbial community. Limnology & Oceanography v. 46 no. 6, p. 1694-1701.

Back to top

Natural Organic Matter Structure and Reactivity

Natural organic matter (NOM) in aquatic systems differs in structure, with land-derived material showing generally higher molecular-weights and greater aromaticity while most aquatic-derived NOM has a smaller average molecular weight, contains more straight-chain organic structures, and also contains a higher fraction of proteins. The variations in structure of NOM at different locations should affect its reactivity toward other molecules, such as small anthropogenic compounds, that may be present in an aquatic system. In this multi-lab project ( a collaboration with R.F. Dias, and P. Hatcher at Old Dominion University) we are characterizing NOM from various aquatic systems using mass spectrometry, chromatography, and spectroscopy techniques, and evaluating its reactivity with isotopically labeled small molecules using IRM-MS and NMR.

Back to top

Organic Sulfur Formation and Sedimentary Sulfur Cycling

The sulfurization of organic matter during early diagenesis is a globally significant biogeochemical process relevant to petroleum formation, global biogeochemical cycles, paleoenvironmental studies, and microbial biogeochemistry. We are working to understand better the biogeochemical controls on the timing and pathways of organic matter sulfurization, in part using the sulfur isotope composition of organic and inorganic sulfur species in various sedimentary environments. Our study sites so far have included the Cariaco Basin, Florida Bay, Effingham Inlet (British Columbia), the Orca Basin ( Gulf of Mexico), and Lake Edward (East Africa), and collaborators on these projects include J. Sinninghe Damsté, S. Schouten, and E. Hopmans at NIOZ, D. Hollander at USF, and T. Lyons at the Univ. Missouri Columbia (MU). As part of this work we have made the first compound specific sulfur isotope measurements on naturally formed organic sulfur compounds.

Publications:

Werne, J.P., D.J. Hollander, T.W. Lyons, E.C. Hopmans, S. Schouten, and J.S. Sinninghe Damsté (In review '07) Investigating pathways of diagenetic organic matter sulfurization using compound-specific sulfur isotope analysis. Submitted to Geochimica et Cosmochimica Acta

Werne, J.P., D.J. Hollander, T.W., Lyons, J.S. Sinninghe Damsté, 2004. Organic sulfur biogeochemistry: Recent advances and future directions for organic sulfur research. In: Sulfur Biogeochemistry: Past and Present. J. Amend, K. Edwards, & T. Lyons, eds. GSA Special Paper 379, Ch. 9 pp. 135-150

Werne, J.P., T.W. Lyons, D.J. Hollander, M.J. Formolo, J.S. Sinninghe Damsté, 2003. Reduced sulfur in euxinic sediments of the Cariaco Basin: sulfur isotope constraints on organic sulfur formation. Chemical Geology v. 195, p. 159-179.

Werne, J.P., D.J. Hollander, A. Behrens, P. Schaeffer, P. Albrecht, J.S. Sinninghe Damsté, 2000. Timing of early diagenetic sulfurization of organic matter: A precursor-product relationship in Holocene sediments of the anoxic Cariaco Basin, Venezuela, Geochimica et Cosmochimica Acta, v. 64, no. 10, pp. 1741-1751.

Back to top

Photoreactivity of Riverine and Estuarine Organic Matter

Rivers deliver terrigenous (land-derived) organic matter (OM) into ocean waters. The structure and history of this OM suggests that it should not be particularly biodegradable. However, isotope and biomarker studies indicate that little terrigenous OM is present in open ocean waters. Photochemistry is believed to be at least a partial solution to this conundrum. Photochemical reactions can cause both direct oxidation of OM to carbon dioxide and conversion of the OM into more edible material that microbes then respire to carbon dioxide. In this study, a collaboration between the Minor lab at UMD and the Mopper lab at Old Dominion University in Virginia, the photochemical reactivity of OM from a temperate river/estuary system is measured two times a year. The resulting changes in chemical composition are measured by a suite of photochemical and geochemical parameters including mass spectrometry, size-exclusion chromatography, UV-Vis light spectroscopy, carbon monoxide production, dissolved inorganic carbon production, and oxygen consumption. The bioavailability of initial and light-exposed OM from each sample site is also evaluated. In addition to actual transects, artificial transects (which vary ionic strength and pH) have also been evaluated using a fresh-water, terrigenous end-member as the organic matter source.

Back to top

Trace metal and nutrient biogeochemistry

Modern processes in large lakes are not well understood. In Lake Superior, for example, we still do not have a detailed understanding of carbon cycling, which may have significant spatial and temporal heterogeneity. Understanding modern lake functioning is critical for interpretation of paleolimnological records and for evaluation of how human activities may affect lake systems.

Publications:

R.M.L. McKay, G.S. Bullerjahn, D. Porta1, E.T. Brown, R.M. Sherrell, T.M. Smutka, R.W. Sterner, M.R. Twiss, and S.W. Wilhelm, in press. Consideration of the bioavailability of iron in the North American Great Lakes, Aquatic Ecosystem Health and Management.

R.W. Sterner, T.M. Smutka, R.L.M. McKay, Qin Xiaoming, E.T. Brown, and R.M. Sherrell, 2004, Phosphorus and trace metal limitation of algae and bacteria in Lake Superior, Limnology and Oceanography, 49, 495-507.

Baehr, M. M. and J. McManus, 2003. The measurement of phosphorus and its spatial and temporal variability in the western arm of Lake Superior. J. Gt. Lakes Res., 29:479-487.

McManus, J., Heinen, E. A., and M. M. Baehr, 2003. Hypolimnetic oxidation rates in Lake superior: Role of dissolved organic material on the lake's carbon budget. Limnol. Oceanog., 48: 1624-1632.

Bootsma, H. A., Hecky, R. E., Johnson, T. C., Kling, H. and Mwita, J., 2003. Inputs, outputs and internal cycling of silica in a large, tropical lake. Journal of Great Lakes Research, v. 29, p. 121-138.

Back to top