My research interests center on modeling the fate of natural and globally dispersed radionuclides and contaminants in aquatic ecosystems, as well as the use of these substances as tracers of ecological processes. For example, Cs isotopes make particularly useful tracers in aquatic food webs because they have simple chemistry, no metabolic use, are taken up directly by primary producers, are taken up through food by consumers and exhibit first order elimination. Cs is also the only inorganic element that biomagnifies.

Aquatic research, which constitutes the bulk of current efforts, consists of three main areas: 1) fish bioenergetics through Cs mass balance modeling, with an emphasis on competitive interactions between native and non-native salmonids; 2) extension of the fish bioenergetics approach to aquatic invertebrates; 3) dynamic modeling of ¹³⁷Cs and other radionuclides in aquatic food webs; 4) development of isotopic techniques for in situ quantification of primary production in streams. Terrestrial research is aimed at developing a new technique for estimating ammonium production in soils.

Field work is primarily conducted in northern Colorado, which has a variety of lakes and streams, from alpine regions to the plains. Some of the invertebrate work is carried out at the Savannah River Ecology Laboratory, South Carolina.

Selected Publications:

Rowan, D.J., J.B. Rasmussen, and L.A. Chant. 1997. A bioenergetics approach to modeling seasonal patterns in the bioaccumulation of radiocesium, p. 399-405. In G. Desmet et al. [ed.] Freshwater and Estuarine Radioecology, Elsevier.

Rowan, D.J. and J.B. Rasmussen. 1996. Measuring the bioenergetic cost of fish activity in situ using a globally dispersed radiotracer (¹³⁷Cs).Canadian Journal of Fisheries and Aquatic Sciences 53: 734-745.

Rowan, D.J. and J.B. Rasmussen. 1995. The elimination of radiocesium from fish. Journal of Applied Ecology 32: 739-744.

Rowan, D.J., R.J. Cornett, K.King and B. Risto. 1995. Sediment focusing and ²¹⁰Pb dating: a new approach. Journal of Paleolimnology 13: 107-118.

Rowan, D.J. and J.B. Rasmussen. 1994. The bioaccumulation of radiocesium by fish: the influence of physico-chemical factors and trophic structure. Canadian Journal of Fisheries and Aquatic Sciences 51: 2388-2410.

Jackson, L.J., D.J. Rowan, R.J. Cornett and J. Kalff. 1994. The role of Myriophyllum spicatum as vector between sediment-bound elements and attached epiphytes. Canadian Journal of Fisheries and Aquatic Sciences 51: 1769-1773.

Rowan, D.J. and J. Kalff. 1993. Predicting sediment metal concentrations in lakes without point sources. Water, Air, and Soil Pollution 66: 145-162.

Rowan, D.J. and J.B. Rasmussen. 1992. Why don't Great Lakes fish reflect environmental concentrations of organic contaminants?--an analysis of between lake variability in the ecological partitioning of PCBs and DDT. Journal of Great Lakes Research 18: 724-741.

Rasmussen, J.B., D.J. Rowan, D.R.S. Lean and J.H. Carey. 1990. Food chain structure in Ontario lakes determines PCB levels in lake trout and other pelagic fish. Canadian Journal of Fisheries and Aquatic Sciences 40: 2030-2038.