Tracy A Villareal

Department of Marine Science

Phytoplankton Ecology

Phone: 361-749-6732

Office Location
S13 L218

Postal Address
The University of Texas at Austin
Mar Sci Inst-Port Aran
750 Channel View Dr
Port Aransas, TX 78373

Ph.D., University of Rhode Island (1989)
M.S., Texas A&M University (1981)
B.S., Texas A&M University (1979)

Research Interest

Phytoplankton Ecology

Ecology of oceanic phytoplankton, transport of nutrients via phytoplankton vertical migration, adaptations to oligotrophic gyres, growth and nitrogen fixation in diatom symbioses

My research interests are in understanding the processes and interactions that structure phytoplankton communities. I have two major research programs focused on the autecology of the oceanic diatom species. My lab uses both field and laboratory studies to understand phytoplankton responses.

My current funding addresses N2 in marine systems from two perspectives. The first are laboratory studies on the growth requirements and N2 fixation rates of diatom-diazotroph symbioses. We have two taxa in culture at the moment: the Hemiaulus symbioses and the Rhizosolenia/Richelia symbioses. Our work is examining growth rates, light and nutrient requirements, and how N2 fixation rates vary in response to changes in these variables. These studies in support of a separate field program in the Gufl of Mexico that is examining N2 fixation in the system and how it is affected by the energetic physical processes in the Gulf (Loop Current, mesoscale eddies and interactions with the Mississippi River plume). This latter work has a field season in 2011, and perhaps in 2012. The recent work in the Gulf of Mexico is complementing a program that recent examined blooms of the diatom symbioses in the Pacific Ocean.

Another favorite theme I like to think about is how diatoms adapt to the oligotrophic, stratified conditions of the open sea. My oceanic work has explored vertical migration in the largest known phytoplankton species. These taxa can range up to several millimeters in diameter. Despite being non-motile (lacking flagella), various dinoflagellates, diatoms and Prasinophytes appear to be capable of extensive vertical migrations. They regulate their buoyancy to sink to sub-nutricline depth (>100 meters), take up nitrate and then return to the surface for photosynthesis. My work has focused on understanding how buoyancy is regulated, growth rates, sinking rates, ascent rates, nitrogen assimilation, and the biogeochemical implications of this biologically mediated N flux.

Selected Publications

Schouten S, T.A. Villareal, Hopmans EC, Mets A, Swanson KM, Damste JSS (2013) Endosymbiotic heterocystous cyanobacteria synthesize different heterocyst glycolipids than free-living heterocystous cyanobacteria. Phytochemistry 85: 115-121

Krause, J. W., M. A. Brzezinski, T. A. Villareal , C. Wilson (2013). Biogenic silica cycling during summer phytoplankton blooms in the North Pacific subtropical gyre. Deep-Sea Research, Part 1. 17: 49-60. s,

Luo, Y.-W., et. al.. (2012) Database of diazotrophs in global ocean: abundance, biomass and nitrogen fixation rates, Earth System Science Data, 4, 47-73, doi:10.5194/essd-4-47-2012.

Krause, J. W, M. A. Brzezinski, T. A. Villareal, C. Wilson. (2012). Increased kinetic efficiency for silicic acid uptake as a driver of summer diatom blooms in the North Pacific Subtropical Gyre. Limnology and Oceanography. 57 (4), 1084–1098. doi:10.4319/lo.2012.57.4.1084

Villareal, T.A., C. G. Brown, M.A. Brzezinski, J. W. Krause, and C. Wilson. (2012). Summer diatom blooms in the North Pacific subtropical gyre: 2008-2009. PLoS ONE 7(4): e33109. doi:10.1371/journal.pone.0033109

Zhong, Y. , Bracco, A., and T.A. Villareal (2012). Pattern formation at the ocean surface: Sargassum distribution and the role of the eddy field. Limnology and Oceanography: Fluids and Environments vol. 2. DOI:10.1215/21573689-1573372.

Schock, T. B, K. Huncik, K. Beauchesne, T. A. Villareal and P. D. R. Moeller. (2011)Identification of Trichotoxin, a novel chlorinated compound associated with the bloom forming cyanobacterium, Trichodesmium thiebautii. Marine Science and Technology. 45 (17) 7503-7509. doi: 10.1021/es201034r

Joye, S.B, I. Leifer, I.R. MacDonald, J. P. Chanton, C.D. Meile, A. P. Teske, J. E. Kostka, L. Chistoserdova, R. Coffin, D. Hollander, M. Kastner, J. P. Montoya, G. Rehder, E. Solomon, T. Treude, T. A. Villareal. (2011). Technical comment on “A Persistent Oxygen Anomaly Reveals the Fate of Spilled Methane in the Deep Gulf of Mexico” by Kessler et al. Science, Washington, D.C. 332, 1033-1034 DOI: 10.1126/science.1203307

Villareal, T. A., L.R. Adornato, and C. Wilson. (2011) Summer blooms of diatom-diazotroph assemblages (DDAs) and surface chlorophyll in the N. Pacific gyre – a disconnect Journal of Geophysical Research-Oceans Vol. 116, C03001, doi:10.1029/2010JC006268

Triggs, R., L. Jarmon, T.A. Villareal. (2010). An Interdisciplinary Design Project in Second Life®: Creating a Virtual Marine Science Learning Environment. International Journal of Virtual and Personal Learning Environments. 1(3): 17-35

  • 2010 IITAP 2010 Top Honor for Creativity in Instructional Innovation, Univ. Texas, Austin
  • 2005 Darbaker Prize, Botanical Society of America
  • 2004 Eisenhower National Clearinghouse Digital Dozen Award for STEAMER website
  • (
  • 1998 Luigi Provosoli Award, Phycological Society of America
  • 1988 Harold C. Bold Award, Phycological Society of America