Natalie Cohen, Ph.D.

Postdoctoral Scholar, Marine Sciences, Woods Hole Oceanographic Institution

Education: University of North Carolina at Chapel Hill, Ph.D., Marine Sciences
Institution: Woods Hole Oceanographic Institution (laboratory of Mak Saito)

Project: Linking trace metal availability with phytoplankton metal metabolism

Trace metals are essential for marine phytoplankton to perform cellular processes including photosynthesis, nitrogen assimilation, and carbon fixation; however, we are currently limited in our understanding of how trace metal distributions influence phytoplankton metal-dependent cellular metabolism in large regions of the open ocean. In particular, it is unclear how shifts in metal availabilities influence metal-containing protein (metalloprotein) usage, and how metal allocations to biochemical pools may vary by taxa. The goal of this proposal is to examine the relationships among trace metal distributions, metalloprotein abundance, and biomarkers of trace metal status in eukaryotic phytoplankton using geochemical, metatranscriptomic and metaproteomic approaches across diverse ocean provinces.

This goal will be addressed through the following research objectives: 1) comparing phytoplankton metalloprotein expression patterns from contrasting water masses of the tropical and equatorial Pacific Ocean, 2) investigating how metal-dependent metabolism is influenced by the addition of iron or cobalt-dependent vitamin B12 in the North Atlantic Ocean, and 3) evaluating correlative patterns in trace metal distributions and metalloprotein abundance through the Tara Oceans repository of metatranscriptomic, trace metal and environmental metadata.

The first objective will be explored through eukaryotic metaproteomes obtained along a latitudinal transect of the tropical and equatorial Pacific Ocean, differing in nitrate, iron, cobalt and nickel concentrations. Biomarkers of iron and cobalt-containing-B12 stress will quantified along the transect, and taxa-specific metalloprotein abundances will be analyzed to determine whether diverse phytoplankton rely on distinct trace metal strategies. The second objective will be examined through mesocosm incubation experiments performed on an upcoming research cruise to the tropical Atlantic Ocean, where trace metal stress may seasonally occur. Combinations of macronutrients (nitrate and phosphate) and micronutrients (iron and B12) will be added to surface seawater to determine how metal-dependent metabolic processes are influenced by changes in metal availability among diverse North Atlantic Ocean phytoplankton assemblages. The third and final objective will be investigated by utilizing the global Tara Oceans metadata and identifying correlative relationships between metalloprotein transcript abundances and trace metal concentrations. These analyses will elucidate how diverse phytoplankton from biogeochemically distinct biomes have structured their metabolism as a function of trace metal regime.

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