A. Robin Stewart

Research Hydrologist

B.S. University of Victoria, Biology
Ph.D. University of Manitoba, Botany

arstewar@usgs.gov

Research Interests
My research focuses on understanding transport, fate and bioaccumulation of trace metals, elements and organic contaminants in aquatic systems. I have studied a range of contaminants including trace elements (metals, Se, Hg) and organochlorine pesticides (PCBs, DDT), in a variety of aquatic systems including lakes and reservoirs, wetlands, estuaries and rivers, and in biota ranging in size from zooplankton to diving ducks and sturgeon. These diverse research interests have led me to a greater understanding of how contaminants behave chemically in the environment, interact with biological systems and manifest their effects in nature. Each research area is of sufficient importance and interest to continue dedicated research on them; however, it is how they interact in a larger ecosystem context that I find most intriguing. In the past, the goal of understanding complex environmental problems in nature was seen as unattainable. However, with new tools and combined approaches from a variety of disciplines I believe we will soon be able to develop ecosystem models that accurately depict mechanisms of contamination at all levels of ecosystem organization. It is only through this level of awareness that will we truly be able to understand chemical stressors and protect our environment.

Selected publications:

Selenium and mercury distribution in food webs of the San Francisco Bay-Delta:

Stewart, A.R., Saiki, M.K., Kuwabara, J.S., Alpers, C.N., Marvin-DiPasquale, M., and Krabbenhoft, D.P. Influence of plankton mercury dynamics and trophic pathways on mercury concentrations of top predator fish of a mining-impacted reservoir. Can.J.Fish.Aquat.Sci. 2008. In press.

Stewart, AR, Luoma, SN, Schlekat, CE, Doblin, MA and Hieb, KA. 2004. Food Web Pathway Determines How Selenium Affects Aquatic Ecosystems: A San Francisco Bay Case Study. Environ. Sci. Technol. 38(17):4519-4526.

Baines, S.B., N.S. Fisher, and A.R. Stewart. 2002. Assimilation of Se and trace metals from food in juvenile striped bass. Limnol. Oceanogr. 47: 646-655.

Stewart, A.R. and others. 2001. Applications of stable isotopes research in understanding complex ecological processes in the San Francisco Estuary. Interagency Ecological Program for the San Francisco Estuary. IEP Newsletter 14 (4): 27-32.

Fate and transport of trace elements and organic chemicals during the 1997 Red River flood:
Stewart, A.R., Stern, G.A., Lockhart, W.L, Kidd, K.A., Salki, A.G., Stainton, M.P., Koczanski, K., Rosenberg, G.B., Savoie, D.A., Billeck, B.N., Wilkinson, P., and Muir, D.C.G. 2003. Assessing Trends in Organochlorine Concentrations in Lake Winnipeg Fish Following the 1997 Red River Flood. J. Great Lakes Res. 29(2):332-354.

Stewart, A.R., Stern, G.A., Salki, A., Stainton, M.P., Lockhart, W.L., Billeck, B.N., Danell, R., Delaronde, J., Grift, N.P., Koczanski, K., MacHutcheon, A., Rosenberg, B., Savoie, D., Tenkula, D., Tomy, G., and Yarchewski, A. 2000. Effects of the 1997 Red River flood on contaminant transport and fate in southern Lake Winnipeg. International Red River Basin Task Force. http://www.ijc.org/pdf/winnipegwaterquality.pdf

Bioavailability and bioaccumulation of trace metals in Precambrian shield lakes in association with Canada's Experimental Lakes Area:
Stewart, A.R. 1999. Accumulation of cadmium by a freshwater mussel (Pyganodon grandis) is reduced in the presence of other metals. Can. J. Fish. Aquat. Sci. 56: 467-478.

Stewart, A.R. and Malley, D.F. 1999. The effect of a metal mixture (Cu, Zn, Pb and Ni) on cadmium bioavailability and accumulation by the freshwater macrophyte Eriocaulon septangulare. Environ. Toxicol. Chem. 18:436-447.

Stewart, A.R. 1998. Effect of a metal mixture (Cu, Zn, Pb and Ni) on the bioavailability and bioaccumulation of cadmium in natural systems. University of Manitoba, Winnipeg, Manitoba.

Malley, D.F., A.R. Stewart and B.D. Hall. 1996. Uptake of methyl mercury by the floater mussel, Pyganodon grandis (Bivalvia, Unionidae), caged in a flooded wetland. Environ. Tox. Chem. 15: 928-936.