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<p>Our next EOAS colloquium speaker will be TODAY at 3:30 in CAR 101:</p>
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<p>Dr. Nicolas Cassar of Duke University</p>
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<b><font size="+2"><span style="font-size: 11pt; color:
black;">Title: Revisiting the biogeography of marine N2 fixation with high-resolution observations</span></font><font size="+2"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black;mso-fareast-language:EN-US"><o:p></o:p></span></font></b></p>
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<div class="WordSection1"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black;mso-fareast-language:EN-US">“The supply of new nutrients to the ocean surface fuels primary production and the export of organic carbon to deep waters. As one
of the main sources of new nitrogen to marine ecosystems, N2 fixation is a microbial process with profound biogeochemical implications. However, the fundamental role that N2 fixation plays in the cycling of nitrogen and carbon stands in sharp contrast to our
poor understanding of its global distribution, a fact largely attributable to current methods that cannot capture the patchy distribution of marine N2 fixation. To ascertain its distribution, our lab recently developed a method for high-frequency underway
measurements of N2 fixation. From our deployment of this new method over large swaths of the western North Atlantic, we located hotpots of marine N2 fixation along the Eastern Seaboard. I will discuss our results in the context of microbial communities and
environmental conditions in this region. Overall, our observations of thriving cyanobacterial diazotrophs in coastal waters challenges the current paradigm of higher N2 fixation in the warm oligotrophic waters of the subtropical gyres.”
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