Dr. Stewart is a biogeochemist with
interest in the interactions between organisms and elemental cycling,
particularly in the ocean. Currently she uses natural radionuclides to
investigate the trophic transfer and bioaccumulation of metals by plankton, as well
as to trace organic carbon cycling in the surface ocean. Her work sheds light
on the mechanisms of contaminant accumulation in ecosystems as well as the
ocean’s potential to sequester atmospheric carbon dioxide, a greenhouse gas.
Further, her research into the behavior of present-day radioactive tracers may
provide insight into the use of naturally-occurring paleotracers in the ocean.
Primarily she has focused her research on the unique, short-lived,
particle-reactive isotope polonium-210. At Queens College she has pursued
regional environmental contaminant studies, done local research on the impacts
of anthropogenic regional warming, and continues her work on large-scale
oceanographic questions. She has been an active participant in the
international GEOTRACES project.
Possible Future and Student
- Metal accumulation and distribution in local coastal
- The influence of dust on carbon assimilation in
- Development of more specific environmental tracers for
- The importance of food web structure in determining
- The effect of different particle types on radioisotope
- Species-specific nutrient uptake and loss in the
My teaching philosophy is very
straight-forward: Tough but fair.
- GEOL 08 Oceanography
- GEOL 25 Natural Resources and the Environment
- ENSCI 99 A Practical Guide to Environmental
- ENSCI 100 Our Planet in the 21st Century
- GEO 356 Advanced Oceanography
- GEO 373 Long Island Sound: Past and Present Climate
- HNRS 228: Honors Seminar: Waterways and Climate in NYC
- HMNS 102: Honors in Math and Na Sciences Directed
- GEO 799.3 Special Topics: Environmental Biogeochemistry
- GEO 799.3 Special Topics: Plankton Ecology
- GEO 791.3 Special Topics: Tracers in the Sea
- GEO 799.3 Special Topics: Environmental Science Course
Publications (selected, for full
list see CV)
Hayes, C. T., Black, E. E., Andersen, R. A., Baskaran, M.,
Buesseler, K. O., Charette, M. A., Cheng, H., Cochran, J. K., Edwards, R. L.,
Fitzgerald, P., Lam, P. J., Lu, Y., Morris, S. O., Ohnemus, D. C., Pavia, F.
J., Stewart, G., and Tang, Y. (2018) Flux
of particulate elements in the North Atlantic Ocean constrained by multiple
radionuclides. Global Biogeochemical Cycles,
Tang, Y., Castrillejo, M., Roca-Martí, M., Masqué, P.,
Lemaitre, N., and G. Stewart (2018) Distributions of 210Po
and 210Pb activities along the North Atlantic GEOTRACES GA01
(GEOVIDE) cruise: partitioning between the particulate and dissolved phase.
Biogeosciences, 15, 5437-5453, https://doi.org/10.5194/bg-15-5437-2018
Tang, Y., Stewart, G., Lam, P. J., Rigaud, S., & Church, T. (2017). The
influence of particle concentration and composition on the fractionation of 210
Po and 210 Pb along the North Atlantic GEOTRACES transect GA03. Deep Sea
Research Part I: Oceanographic Research Papers. doi.org/10.1016/j.dsr.2017.09.001
Schallenberg, C., Ross, A. R., Davidson, A. B., Stewart, G. M., & Cullen, J. T. (2017). Temporal variability of dissolved iron species in the mesopelagic zone at Ocean Station PAPA. Journal of Marine Systems, 172, 128-136.
Rice E.J. and G. Stewart (2016) Decadal changes in zooplankton abundance and
phenology of Long Island Sound reflect interacting changes in temperature and
community composition. Marine Environmental Research, 120, 154-165. doi.org/10.1016/j.marenvres.2016.08.003
Mackinson, B. L., Moran, S. B., Lomas, M. W., Stewart, G. M., & Kelly, R. P. (2015). Estimates of micro-, nano-,
and picoplankton contributions to particle export in the northeast Pacific.
Biogeosciences, 12(11), 3429-3446. doi.org/10.5194/bg-12-3429-2015
Seebaugh DR, Wallace WG, L’Amoreaux WJ, Stewart GM
(2012) Assimilation of elements and digestion in grass shrimp pre-exposed to
dietary mercury. Archives of Environmental Contamination and Toxicology, 63(2), 230-240. doi.org/10.1007/s00128-011-0493-7
Moran, S.B., Lomas M., and Kelly, R.P. (2010) Direct comparison of 210Po,
234Th and POC particle-size distributions and export fluxes at the
Bermuda Atlantic Time-series Study (BATS) site. Journal of Environmental
Radioactivity, 102 (5), 479-489. doi.org/10.1016/j.jenvrad.2010.09.011
Buesseler K., Benitez-Nelson C., Moran S. B., Burd
A., Charette M., Cochran J.K., Coppola L., Fisher N., Fowler S., Gardner W.,
Guo L., Gustafsson O., Lamborg C., Masque P., Miquel J-C., Passow U., Santschi
P., Savoye N., Stewart G., Trull T., (2006) An assessment of particulate
organic carbon to thorium-234 ratios in the ocean and their impact on the
application of 234Th as a POC proxy. Marine Chemistry, 100, 213-233. doi.org/10.1016/j.marchem.2005.10.013
Stewart G.M., S.W.
Fowler, J.L. Tessyie, O. Cotret, and N.S. Fisher (2005) Contrasting the
transfer of polonium-210 and lead-210 across three trophic levels in the marine
plankton. Marine Ecology Progress Series, 290,
Liu X.F., G.M. Stewart, J.K. Cochran, C. Lee, R.A. Armstrong, D. Hirschberg, J.C.
Miquel, and B. Gasser (2005) Constraints on the differences between POC
measured in samples from Niskin bottles and in-situ pumps. Deep Sea Research I,
Stewart G.M. and
N.S. Fisher (2003) Bioaccumulation of polonium-210 in marine copepods.
Limnology and Oceanography, 48(5),