Armbrust Lab

Research Scientist

Phone: 206-685-4196

e-mail: amarchetti-at-ocean.washington.edu

Education:

B.Sc. Biology, McGill Univeristy, Montreal PQ (1998)

Ph.D. Botany, University of British Columbia, Vancouver BC (2005)

Research Interests:

My primary research focus is biogeochemical evolution of phytoplankton in marine environments. Biogeochemical evolution is defined as the changes in the genomes of organisms and in the chemistry of their environment, as they influence each other over time. I combine laboratory-based and field-based studies to answer fundamental questions on factors influencing phytoplankton distributions and abundance, and to advance our understanding of how these organisms interact with their environment and influence ocean biogeochemistry. I am interested in studying trace metals, such as iron, that are essential for the nutrition of phytoplankton and how future climate changes will influence phytoplankton growth and ecology. For example, we have discovered that pennate diatoms such as Pseudo-nitzschia contain the gene to encode for ferritin, which is a highly specialized iron concentrating protein. The acquisition of ferritin by certain diatoms may contribute to their success in low-iron environments where new inputs of iron are primarily confined to pulse events through atmospheric dust deposition. More details about this study may be found here.  I also study how growing phytoplankton impact ocean nutrient inventories by measuring biological rate processes. Several approaches are taken to my investigations. First, I work with marine isolates of diatoms in the laboratory, which allows for refined studies to determine the molecular biology and physiology of a specific group of phytoplankton. Second, I participate on research cruises to investigate natural phytoplankton assemblages, as this provides for a more ecologically relevant context to assess how these organisms acclimate and adapt to different environments and how their nutrient requirements will influence marine biogeochemistry.

Publications:

• Marchetti A, Varela DE, Lance V, Johnson Z, Palmucci M, Giordano, M and Armbrust EV. (2010)  Iron and silicic acid effects on phytoplankton productivity, diversity and chemical composition in the central equatorial Pacific Ocean. Limnology and Oceanography. 55: 11-29. Link to paper
• Marchetti A and Cassar N. (2009) Diatom elemental and morphological changes in response to iron limitation: a brief review with paleoceanographic applications. Geobiology. 7: 419-431. Link to paper
• Zhang Z, Sachs JP and Marchetti A. (2009) Hydrogen isotope fractionation in freshwater and marine algae: II. Temperature and nitrogen-limited growth rate effects. Organic Geochemistry. 40: 428-439. Link to paper
• Marchetti A, Parker MS, Moccia LP, Ostlund EL, Arrieta A, Ribalet, F, Murphy MEP, Maldonado MT and Armbrust EV. (2009) Ferritin is used for iron storage in bloom-forming marine pennate diatoms. Nature. 457, 467-470. link to paper
• Marchetti A, Lundholm N, Kotaki Y, Hubbard KA, Harrison PJ and Armbrust EV. (2008) Identification and assessment of domoic acid production in oceanic Pseudo-nitzschia (Bacillariophyceae) from iron-limited waters in the NE Subarctic Pacific. Journal of Phycology 44, 650-661. link to paper
• Marchetti A and Harrison PJ. (2007) Coupled changes in the cell morphology and the elemental (C, N and Si) composition of oceanic and coastal species of the pennate diatom Pseudo-nitzschia due to iron deficiency. Limnology and Oceanography 52, 2270-2284. link to paper
• Marchetti A, Sherry ND, Kiyosawa H, Tsuda A and Harrison PJ. (2006) Phytoplankton processes during a mesoscale iron enrichment in the NE subarctic Pacific: Part I - biomass and assemblage. Deep-Sea Research II 53, 2095-2113. link to paper
• Marchetti A, Juneau P, Whitney FA, Wong CS and Harrison PJ. (2006) Phytoplankton processes during a mesoscale iron enrichment in the NE subarctic Pacific: Part II - nutrient utilization. Deep-Sea Research II 53, 2114-2130. link to paper
• Marchetti A, Sherry ND, Juneau P, Strzepek RF and Harrison PJ. (2006) Phytoplankton processes during a mesoscale iron enrichment in the NE subarctic Pacific: Part III - primary productivity. Deep-Sea Research II 53, 2131-2151. link to paper
• Marchetti A, Maldonado MT, Lane ES and Harrison PJ. (2006) Iron requirements of the pennate diatom Pseudo-nitzschia: Comparison of oceanic (HNLC) and coastal species. Limnology and Oceanography 51, 2092-2101. link to paper
• Scarratt MG, Marchetti A, Rivkin RB, Hale M et al. (2006) Assessing microbial responses to iron enrichment in the subarctic Northeast Pacific: Do microcosms reproduce the in situ condition? Deep-Sea Research II 53, 2182-2200. link to paper
• Needoba JA, Marchetti A, Henry M, Wong CS, Johnson K, and Pedersen TF. (2006) Stable nitrogen isotope dynamics during a mesoscale iron enrichment in the NE Subarctic Pacific. Deep-Sea Research II 53, 2214-2230. link to paper
• Levasseur, M et al. (2006) DMSP and DMS dynamics during a mesoscale iron fertilization experiment in the Northeast Pacific. Part I. Temporal and vertical distributions. Deep-Sea Research II 53, 2353-2369 link to paper
• de Baar et al. (2005) Synthesis of 8 iron fertilization experiments from the iron age in the age of enlightenment. Journal of Geophysical Research 110, C09S16, doi:10.1029/2004JC002601 link to paper
• Marchetti A, Trainer VL, Harrison PJ. (2004) Environmental conditions and phytoplankton dynamics associated with Pseudo-nitzschia abundance and domoic acid in the Juan de Fuca eddy. Marine Ecology Progress Series 281, 1-12. link to Paper
• Boyd et al. (2004) The decline and fate of an iron-induced subarctic phytoplankton bloom. Nature 428, 549-552. link to paper