Diatoms are significant contributors to carbon expor,t even in HNLC regions. To understand how changes in diatom metabolism in reaction to environmental variables might alter their role in food web dynamics and carbon export, we conducted metatranscriptome analysis of a time-series of surface water samples paired with incubation experiments with manipulated nutrients. Sampling was conducted as part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign conducted late summer in the HNLC subarctic Pacific.  Diatom communities were taxonomically and metabolically similar across three weeks of sampling, consistent with similarities in surface water N, P, Si and growth-limiting Fe concentrations. In situ diatom communities demonstrated upregulation of metabolism consistent with Fe stress. Experimental alleviation of Fe stress revealed genera-specific responses in expression of photosynthetic components and in glycan, carbohydrate, amino acid and lipid metabolism. Taxonomic comparison of responses within in situ communities reveals that Fe-sensitive metabolism in Pseudo-nitzschia spp. is uniquely and favorably adapted to low Fe environments with other taxa (e.g. Chaetoceros and Thalassiosira spp.) showing much higher regulatory impacts of low Fe on Fe-sensitive pathways. Taken together, our data show that this HNLC environment differently impacts potential nutritional quality and carbon fixation amongst prevalent diatoms with implications for food webs and carbon export. 

Primary Presenter: Bethany Jenkins, University of Rhode Island (bjenkins@uri.edu)

Authors:

Bethany Jenkins, University of Rhode Island  (bjenkins@uri.edu)

Sarah Lerch, Institute of Marine Research, Flødevigen Research Station, Norway  (sarah.lerch@hi.no)

Kristofer Gomes, University of Rhode Island  (kristofer_gomes@uri.edu)

Kristen Buck, Oregon State University  (kristen.buck@oregonstate.edu)

Mark Brezinski, Marine Science Institute, University of California Santa Barbara  (markbrzezinski@ucsb.edu)