Research Insights

Despite significant advancements in our knowledge of marine microbial ecology over the past few decades, gaps remain in our understanding of microeukaryote diversity and physiology across vast regions of the open ocean, and how they contribute to community ecology and biogeochemistry. In an effort to address this, we combined omic and physicochemical measurements across a ~4,600 km section of the central Pacific Ocean, traversing oligotrophic gyres and the equatorial upwelling zone. A surprising finding was the relative abundance of dinoflagellates in these offshore communities, which are commonly observed in coastal settings but less understood in the open ocean. They were detected throughout the surface and mesopelagic, with distinct functional profiles between depth zones. Surface communities showed indications of phototrophic carbon fixation and potentially mixotrophy (both phototrophy and heterotrophy), while deep communities reflected nutrient cycling and degradation, suggesting this group is ecologically successful across a vast region of the ocean. In addition, metabolic signatures based on both dinoflagellate transcripts and proteins indicated metabolic plasticity in response to variable nitrogen and iron regimes, with ironstressed physiology in equatorial upwelling surface waters and nitrogen stress in the oligotrophic gyres. I led the data integration, performed the computational comparisons, and wrote the manuscript. This work has led to new questions I am interested in addressing, including whether surface and deep prostistan populations are taxonomically connected, how long proteins from the surface ocean can remain intact after sinking below the euphotic zone, and the ecological roles of mixotrophy in offshore environments.

Funder: Simons Foundation 

Amount: $810,000 

PI: Natalie Cohen, Franklin College of Arts and Sciences, Department of Marine Sciences