Biological Oceanography and Biogeochemical Cycling

Romberg Tiburon Center

(415) 338-3518

rdugdale@sfsu.edu

userwww.sfsu.edu/~phytopl

Research Interests

I am interested in biogeochemical cycling and the interaction of phytoplankton, nutrients and CO2 . My career has centered on the concept of new production and its application particularly to upwelling ecosystems. I pioneered the use of the stable isotope 15 N in aquatic studies and these led to the ability to separate primary production by phytoplankton based on the input of "new" nutrients and on regenerated nutrients. The concept allows the estimate of primary production available for export up the food chain or downward to the deep sea and sediments. Recently I have considered the role of silicate and constructed a silicate pump mathematical model linking silicate with nitrogen cycling for upwelling systems. This model has had considerable success in answering the question "why isn't the equator greener?" and is likely to be applied to other areas of the ocean. I am interested in the role of the equatorial Pacific upwelling system in regulation of atmospheric CO2 and in the conditions that change that role in geological/climate-change time, primarily through changes in silicate source concentrations, and possible links to glaciation cycles. Our silicate-limited productivity model has been incorporated into a general circulation model run on super computers for the Pacific Basin. Current research is mostly on the role of diatoms in importing nitrogen into the primary production system, passed on to the microbial loop through grazing, thereby separating the primary production system into a high new production, large phytoplankton component, and a low new production, high regenerated production, small phytoplankton component. The field studies in support of this hypothesis are carried out in San Francisco Bay and nearby offshore waters. Since we often encounter El Niño conditions in our cruises this event has also become a research interest.

Selected Papers

Strutton, P G.; Chavez, F.P.; Dugdale, R.C.; Hogue, V. 2004. Primary productivity in the central equatorial Pacific (3°S 130°W) during GasEx-2001. Journal of Geophysical Research,Vol.109,No.C8,C08S06, .1029/2003JC001790.

Dugdale, R. C.; Lyle, M.; Wilkerson, F. P.; Chai, F.; Barber, R. T.; Peng, T.-H. Influence of equatorial diatom processes on Si deposition and atmospheric CO2 cycles at glacial/interglacial timescales, Paleoceanography,Vol.19,No.3,PA3011, 10.1029/2003PA000929.

Cloern, J. E., T. S. Schraga, C. B. Lopez, N. Knowles, R. Labiosa, R. Dugdale. 2005. Climate anomalies generate an exceptional dinoflagellate bloom in San Francisco Bay . Geophysical Research Letters, vol. 32, l14608, doi:10.1029/2005GL023321.

Wilkerson, F.P., R.C. Dugdale, V.E. Hogue and A. Marchi. 2006. Phytoplankton blooms and nitrogen productivity in San Francisco estuary. Estuaries and Coasts 29: 401-416.

Takabayashi, M., K. Lew, A. Johnson, A. Marchi, R. Dugdale, F.P. Wilkerson. 2006. The effect of nutrient availability and temperature on chain length of the diatom, Skeletonema costatum . Journal of Plankton Research 28: 831-840.

Parker, A.E., J. Fuller and R.C. Dugdale. 2006. Estimating dissolved inorganic carbin concentrations from salinity in San Francisco Bay for use in 14C- primary production studies. Interagency Ecological Program Newsletter 19 (3) 17-22.

Wilkerson, F.P. R.C. Dugdale, A. Marchi, V. Hogue, A. Lassiter. The phytoplankton bloom response to wind events and upwelled nutrients during the CoOP-WEST study. Deep-Sea Research II 53: 3023-3048.

Lassiter, A.M, F. Wilkerson, R.Dugdale and V. Hogue. Functiona phytoplankton groups in the CoOP-West upwelling region: the Chaeteoceros complex. Deep-Sea Research II 53: 3063-3077.

Dugdale, R.C., F.P. Wilkerson, A.Marchi and V.Hogue. Nutrient controls on new production in the Bodega Bay, California, coastal upwelling plume. Deep-Sea Research II 53: 3049-3062.

Dugdale, R.C., F. P. Wilkerson, F.Chai, R. Feely. 2007 Size fractionated nitrogen uptake measurements in the Equatorial Pacific and confirmation of the low Si-HNLC condition. Global Biogochemical Cycles, In press.

Dugdale, R.C., F.P. Wilkerson, V.E. Hogue and A. Marchi. 2007. Spring phytoplankton bloom development in San Francisco Estuary: the role of ammonium and nitrate. Estuarine, Coastal and Shelf Science. In press.