Adrian Marchetti

Post-doctoral Research Associate

Phone: 206-685-4196

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

 

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. Currently I am studying iron homeostasis in marine pennate diatoms. Our group has recently discovered that pennate diatoms such as Pseudo-nitzschia contain the gene to encode for ferritin, which is a highly specialized iron concentrating protein. We hypothesize 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. 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 ocean environments and how their nutrient requirements will influence ocean biogeochemistry.


A Scanning Electron Microscope (SEM) image of the marine
pennate diatom Pseudo-nitzschia turgidula isolated from the
NE Pacific

 

Ph.D Thesis Research:

Ecophysiological Aspects of Iron Nutrition and Domoic Acid Production in Oceanic and Coastal Diatoms of the Genus Pseudo-nitzschia My dissertation research with Paul J. Harrison at the University of British Columbia focused on investigating the effects of iron limitation in marine phytoplankton. I participated in the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) which took place at Ocean Station Papa (144.45°W, 50.20°N) in the summer of 2002. In vast regions of the world’s oceans, phytoplankton, in particular diatoms, are growth-limited by low concentrations of the micronutrient, iron. SERIES was performed to determine the phytoplankton response to iron enrichment in low iron waters of the NE subarctic Pacific. The magnitude, duration and composition of the phytoplankton response to the iron enrichment clearly depicted a major shift in the structure of the algal assemblage to a dominance by large diatoms. I also studied the elemental (C,N,Si and Fe) composition and toxicity of the pennate diatom, Pseudo-nitzschia spp. This diatom genera is a universal respondent to iron enrichments in high-nutrient, low chlorophyll (HNLC) regions, whereas in coastal waters, they are widely acknowledged as a harmful algal bloom (HAB)-forming diatom due to their production of the neurotoxin, domoic acid.


A satellite image of surface chlorophyll in the
NE Pacific in August of 2002 displaying the
SERIES phytoplankton bloom (circled)

 

Peer-reviewed Publications:

  • 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

Photo Credits: § SeaWiFS satellite image coutesy of Jim Gower (IOS).