Craig Tobias

(Ph.D., College of William and Mary) Professor of Marine Sciences

Much of my research targets nutrient pollution in the coastal zone. Nearly 40% of the Earth’s population resides within 100km of the coast. The growth of coastal communities is accompanied by increased nutrient delivery that impacts the marine environment in serious but often unpredictable ways. My research program focuses on numerous aspects of nutrient cycling, fate, and transport along an aquatic continuum from watersheds to the coastal ocean. Hydrologic and stable isotope tracer techniques are my primary tools. Presently funded projects examine these topics in tidal creeks, estuaries, and coastal embayments of the Mid Atlantic, and on the salt marshes of the Gulf Coast. Much of my work quantifies element processing rates in situ, and examines the interaction among hydrology, geochemistry, and biology in regulating overall fate, transport, and cycling of important macroelements (nitrogen, carbon, oxygen, sulfur, and phosphorus).

Click here for more information about my current research projects.

Research Projects

Benthic Microalgal Regulation of Carbon and Nitrogen Turnover in Land-Margin Systems: A Dual Isotope Tracer Approach: – National Science Foundation – DEB – Ecosystems

Hydraulic exchange and nutrient reactivity in the wetlands of the New River estuary – DOD/SERDP, Defense Coastal/Estuarine Research Program (DCERP)

Linking hydrogeomorphology and denitrification in the tidal freshwater region of coastal streams – National Science Foundation – EAR – Hydrologic Sciences

Implication of ANAMMOX community structure and microbial interactions in estuarine N removal processes – National Science Foundation – OCE – Biological Oceanography

Oceanography Students

Anna Mudahy – M.Sc. Student

Patrick Plummer – Ph.D. Student

Peter Ruffino – M.Sc. Student

Oceanography Alumni

Mark Ballentine – Ph.D. 2017

Nikki Chang – M.Sc. 2014

Jenay Guardiani – M.Sc. 2013

Faith Raymond – M.Sc. 2015

Amanda Vieillard – M.Sc. 2017

Research Assistant

Sydney Twarz

Postdoctoral Research Associate

Thivanka Ariyarathna


Hardison, A., Canuel, E., Tobias, C., Anderson, I., and Veuger, B. In Review. Carbon and nitrogen dynamics in shallow photic systems: Interactions between macro- and microalgal communities.  For submission to: Limnology & Oceanography.

Tobias, C. and Bohlke, J.K. In Review. Biological and Geochemical Controls on Diel Dissolved Inorganic Carbon Cycling in a Low-order Agricultural Stream: Implications for Reach Scales and Beyond. Chemical Geology.

Hardison, A., Tobias, C., Stanhope, J., Canuel, E., and Anderson, I. In press. An experimental apparatus for laboratory and field-based perfusion of sediment pore water with dissolved tracers. Estuaries and Coasts.

Tobias, C.R., Bohlke, J.K., and Harvey, J.W. 2009 A simple technique for measuring time-variable gas transfer in surface waters. Limnology and Oceanography Methods, 7:185-195.

Tobias, C.R., and Neubauer, S. 2009. Salt marsh biogeochemistry-an overview. In: Cahoon, D., Perillo, G., Wolansky, E., and Brinson, M. (eds), Coastal Wetlands: an ecosystem approach. Elsevier Press. p. 445-492.

Alexander, R.A., Böhlke, J.K., Boyer, E.W., David, M.B., Harvey, J.W., Mulholland, P.J., Seitzinger, S.P., Tobias, C.R., Tonitto, C., and Wollheim, W.M.. 2009. Hydrological and biochemical effects on stream denitrification and nitrogen loads in river networks. Biogeochemistry. DOI 10.1007/s 10533-008-9274-8

Fennel, K., Brady, D., DiToro, D., Fulweiler, R.W., Gardner, W.S., Giblin, A., McCarthy, M.J., Rao, A., Seitzinger, S., Thouvenot-Korppoo, M., and Tobias, C. 2009. . Modelling denitrification in aquatic sediments. Biogeochemistry. DOI 10.1007/s10533-008-9270-z

Fry, B., Cieri, M., Hughes, J., Tobias, C., Deegan, L.A., and Peterson, B. 2008. Stable isotope monitoring of benthic-pelagic coupling with salt marsh fish. Marine Ecology Progress Series, 369: 193-204.

Bratton, J.F., Böhlke, J.K., Krantz, D.E. and Tobias, C.R. 2009. Flow and geochemistry of groundwater beneath a back-barrier lagoon: the subterranean estuary at Chincoteague Bay, Maryland. Marine Chemistry, 113: 78-92.

Dale, O., Song, B.K., and Tobias, C.R. 2009. Biogeographical distribution of diverse anaerobic ammonium oxidizing (ANAMMOX) bacteria in Cape Fear River Estuary. Environmental Microbiology. Doi.10.1111/j.1462-2920.2008.01850.x.

Polito, M., Emslie, S., and Tobias C. 2009. Tissue-specific isotopic discrimination factors in Gentoo penguin (Pygoscelis Papua) egg components: implications for dietary reconstruction using stable isotopes. Journal of Experimental Marine Biology and Ecology 372: 106-

Tobias C., Böhlke, J.K., and J.W. Harvey. 2007. The oxygen-18 isotope approach for measuring aquatic metabolism in high productivity waters. Limnology and Oceanography, Vol 52: 1439-1453.

Seitzinger, S., Harrison , J.A., Böhlke, J.K., Bouwman, A.F., Lowrance, R., Peterson, B., Tobias C., and G. Van Drecht. 2006. Denitrification across landscapes and waterscapes: A synthesis. Ecological Applications. Vol. 16, 2064-2090.

Jarnegren, J, Tobias, C.R, Macko, S.A. and C.M. Young. 2005. Egg predation fuels unique species association at hydrocarbon seeps. Biol. Bull. Vol. 209: 87-93.

Tobias, C.R., Cieri, M., Peterson, B.J., Deegan, L.A., Vallino, J., and Hughes, J. 2003. Processing watershed-derived nitrogen in a well-flushed New England estuary. Limnology and Oceanography Vol. 48: 1766-1778.

Tobias, C.R., Giblin, A.E.. McClelland, J., Tucker, J., and Peterson, B.J. 2003. Sediment DIN fluxes and preferential recycling of benthic microalgal nitrogen in a shallow macrotidal estuary. Marine Ecology Progress Series. Vol. 257: 25-36.

Tobias, C.R., Anderson, I.C., Canuel, E.A., and Macko, S.A. 2001 Nitrogen cycling through a fringing marsh-aquifer ecotone. Marine Ecology Progress Series. Vol. 210: 25-39.

Tobias, C.R., Harvey, J.W., and Anderson, I.C. 2001 Quantifying groundwater discharge through fringing wetlands to estuaries: Seasonal variability, methods comparison, and implications for wetland-estuary exchange. Limnology and Oceanography. Vol. 46(3): 604-615.

Tobias, C.R., Macko, S.A., Anderson, I.C., Canuel, E.A., and Harvey, J.W. 2001. Tracking the fate of a high concentration groundwater nitrate plume through a fringing marsh: A combined groundwater tracer and in situ isotope enrichment study. Limnology and Oceanography. Vol 46: 1977-1989 (feature article).

Anderson, I.C., Tobias, C.R., Macko, S.A., and, Poth M.A. 2000. Sources and sinks of nitrogen in acidified glacial lakes of the Bohemian Forest, Czech Republic. Silva Gabreta.,Vol. 4: 135-146.

Bytnerowicz, A., Godzik, S., Poth, M., Anderson, I., Szdzuj, J., Tobias, C., Macko, S., Kubiesa, P., and Fenn, M. 1999. Chemical composition of air, soil, and vegetation in forests of the Silesian Beskid Mountains, Poland. Water Air and Soil Pollution. Vol. 116: 141-150.

Anderson, I.C., Tobias, C.R., Neikirk, B.B., and Wetzel, R.L. 1997. Development of a process-based nitrogen mass balance model for a Virginia Spartina alterniflora saltmarsh: Implications for net DIN flux. Marine Ecology Progress Series. Vol. 159: 13-27.

Canuel, E., Anderson, I., and Tobias, C. 1997. Organic carbon abundance, distribution and metabolism at the Oyster, Virginia study site. Final Data Report submitted to: Batelle Pacific Northwest National Laboratory.

Beretta, G., and Tobias, C. 1992. Monitoring water quality in Virgin Islands National Park. Park Science. Vol. 12(2): 11-12.

Rogers, C.S., McLain, L.N., and Tobias, C.R. 1991. Effects of Hurricane Hugo (1989) on a coral reef in St. John, USVI. Marine Ecology Progress Series. Vol. 78(2): 189-199.

Rogers, C.S., McLain, L.N., and Tobias, C.R. 1990. Damage to marine resources in Virgin Islands National Park: Often out of sight, but no longer out of mind. Proceedings of the 1990 Congress on Coastal and Marine Tourism. Vol.1: 132-137.


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