James W. McClelland 

Assistant Professor, Department of Marine Science  Research Assistant Professor, Marine Science Institute and Environmental Science Institute Ph.D., Boston University (1998)  B.S., University of Washington (1991)  Home page (Under Construction)

Land-Sea Coupling/Coastal Ecosystem Dynamics/Biogeochemistry

Effects of human activity on water, carbon, and nutrient fluxes from land to sea; responses of estuarine and coastal food webs to changes in land-derived resources; use of stable isotopes and other natural tracers to follow water and water-borne constituents across the land-sea interface.

Research Interests

Environmental changes as a consequence of human activity, including changes in land use, land cover, and global warming, provide the context for much of my work. These changes are having a profound influence on the transport of water and water-borne constituents from land to sea. In turn, changes in the fluxes of water, carbon, and nutrients to estuaries and the coastal ocean are altering fundamental ecosystem properties such as primary production and food web structure. Changes in land-sea fluxes have broader implications as well, including alteration of the global carbon budget and potential impacts of freshwater inputs on global ocean circulation and climate. To identify and explore changes in land-sea coupling I use a wide variety of approaches including analysis of historic data sets, field studies of biogeochemical cycling and constituent transport, and modeling. In my field studies, I frequently take advantage stable isotopes and other natural markers to track the fate of water, organic matter, and nutrients from land through estuarine and marine systems.

I am currently working on three interrelated projects that focus on changes in hydrology and biogeochemistry in response to warming in the Arctic.

1. In fall 2002, I began a 5-year collaborative effort with U.S., Russian, and Canadian scientists to quantify constituent fluxes from the six largest rivers draining the pan-arctic watershed. This project was named PARTNERS in recognition of the many dedicated individuals cooperating to make it a success. . Our overall objective in this project was to use river water chemistry to study the origins and fate of continental runoff in the Arctic. PARTNERS officially ended in fall 2007, but our work on the major arctic rivers will continue at least through 2010 as a component of the burgeoning Arctic Observing Network (AON), a core contribution to the 2007-2008 International Polar Year (IPY). Within this context, our program focusing on the six largest arctic rivers is now identified as the Arctic Great Rivers Observatory (Arctic-GRO). This work is funded by the National Science Foundation.
    

2. In winter 2005, I began a 3-year collaborative project looking at discharge-constituent flux relationships in a set of smaller rivers on the North Slope of Alaska. As with the larger rivers, we are interested in the origins and fate of the river waters. In addition, we are developing modeling tools and analytical approaches that will help us to estimate contemporary and future fluxes of water, carbon, and nutrients from other small coastal watersheds around the Arctic that are less accessible for field studies. This work is funded by the National Science Foundation.
    

3. In summer 2005, I began a 3-year collaborative effort focusing on the carbon budget of the Arctic. Our primary objective in this project is to couple previously independent models of the land, ocean, and atmosphere domains. Incorporation of land-ocean fluxes is a critical step in the development of the coupled model. Once completed, we will use the coupled model to explore contemporary and future carbon dynamics. This work is funded by the National Science Foundation.

I am also working on two new projects closer to home. Like my work in the Arctic, these projects emphasize changes in hydrology and biogeochemistry in response to human activities. However, proximate drivers such as land use and increasing demand for fresh water are major considerations in addition climate change.

1. In spring 2007, I began working with colleagues at UT-Austin, UT-San Antonio, and Texas A&M Corpus Christi on development of a model to explore how linked upland and estuarine ecosystems respond to changes in hydrology and biogeochemistry as a consequence of changes in climate, water use, and land use/cover characteristics. The model is being developed and calibrated on a pair of major Texas watersheds of similar size and contrasting land use/cover characteristics – the Nueces watershed and the San Antonio/Guadalupe watershed. My specific role in the project is to empirically define the relationships between watershed characteristics, hydrographic conditions, and water chemistry. A combination of archived data and new measurements are being used to define these relationships. While ample data exist for low flow conditions, very few data exist for storm events. Thus, our field program specifically targets such events. Capturing these events is important because a large proportion of watershed export to estuaries of south Texas occurs during a few major storm events each year. This project, funded by the National Aeronautics and Space Administration, will continue into 2010.
    

2. In summer 2007, I began working on land-ocean linkages in the Mission-Aransas National Estuarine Research Reserve. Unlike the projects listed above, this work is not coupled to a large collaborative framework. However, the proximity of the NERR to the UTMSI makes it an excellent target for class field trips, undergraduate research projects, and independently funded graduate work. Rae Mooney (graduate student) is currently working on a two-year thesis project titled “Watershed Export Events and Ecosystem Responses in the Mission-Aransas Estuarine Research Reserve” that is supported by a NERR Graduate Research Fellowship. Stephanie Diaz (undergraduate) conducted a summer research project on nitrate dynamics in the Mission and Aransas rivers with support of a National Science Foundation Research Experiences for Undergraduates grant through the UT Environmental Science Institute.

Selected Publications

Holmes, R. M., J. W. McClelland, P. A. Raymond, B. B. Frazer, B. J. Peterson, and M. Stieglitz. 2008. Lability of DOC transported by Alaskan rivers to the Arctic Ocean. Geophys. Res. Lett., 35, L03402, doi:10.1029/2007GL032837.

McClelland, J. W., M. Stieglitz, F. Pan, R. M. Holmes, and B. J. Peterson. 2007. Recent changes in nitrate and dissolved organic carbon export from the upper Kuparuk River, North Slope, Alaska. J. Geophys. Res., 112, G04S60, doi:10.1029/2006JG000371.

Raymond, P. A., J. W. McClelland, R. M. Holmes, A. V. Zhulidov, K. Mull, B. J. Peterson, R. G. Striegl, G. R. Aiken, and T. Y. Gurtovaya. 2007. Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers. Global Biogeochem. Cycles, 21, GB4011, doi:10.1029/2007GB002934.

Peterson, B.J., J. McClelland, R. Curry, R.M. Holmes, J.E. Walsh, and K. Aagaard. 2006. Trajectory shifts in the arctic and subarctic freshwater cycle. Science 313:1061-1066.

McClelland, J.W., S.J. Déry, B.J. Peterson, R.M. Holmes, and E.F. Wood. 2006. A pan-arctic evaluation of changes in river discharge during the latter half of the 20th century. Geophys. Res. Lett., 33, L06715, doi:10.1029/2006GL025753.

Cooper, L., R. Benner, J. McClelland, B. Peterson, R. Holmes, P.A. Raymond, D. Hansell, J.M. Grebmeier, and L.A. Codispoti. 2005. Linkage among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean. J. Geophys. Res. 110, G02013, doi:10.1029/2005JG000031.

McClelland, J.W., R.M. Holmes, B.J. Peterson, and M. Stieglitz. 2004. Increasing river discharge in the Eurasian Arctic: Consideration of dams, permafrost thaw, and fires as potential agents of change. J. Geophys. Res. 109, D18102, doi:10.1029/2004JD004583.

McClelland, J.W., C.M. Holl, and J.P. Montoya. 2003. Attributing low δ15N values of zooplankton to an N2-fixing source in the tropical North Atlantic: Insights provided by stable isotope ratios of amino acids. Deep-Sea Res. I, 50:849-861.

Peterson, B.J., R.M. Holmes, J.W. McClelland, C.J. Vorosmarty, R.B. Lammers, A.I. Shiklomanov, I.A. Shiklomanov, and S. Rahmstorf. 2002. Increasing river discharge to the Arctic Ocean. Science 298:2171-2173.

Valiela, I., M. Geist, J. McClelland, and G. Tomasky. 2000. Nitrogen loadings from watersheds to estuaries: Verification of the Waquoit Bay Nitrogen Loading Model. Biogeochemistry 49:277-293.

McClelland, J.W. and I. Valiela. 1998. Linking nitrogen in estuarine producers to land-derived sources. Limnol. Oceanogr. 43:577-585.

McClelland, J.W. and I. Valiela. 1998. Changes in food web structure under the influence of increased anthropogenic nitrogen inputs to estuaries. Mar. Ecol. Prog. Ser. 168:259-271.

Contact: James W. McClelland
Modified: Friday, February 15, 2008