DIVERSITY AND DYNAMICS OF EUKARYOTIC PICOPLANKTON IN THE NORTH PACIFIC SUBTROPICAL GYRE
Diverse eukaryotic picoplankton have a substantial impact on ocean ecosystems by contributing to both photosynthetic energy capture and heterotrophic consumption of organic matter. Yet, temporal variability of open ocean picoeukaryote communities remains largely unknown. Spatio-temporal dynamics of epipelagic picoeukaryote community composition and diversity were assessed through sequencing of 18S rRNA gene fragments from DNA collected near-monthly between February 2011 and May 2013 at Station ALOHA in the North Pacific Subtropical Gyre (NPSG). Operational taxonomic units (delineated at 97% 18S rRNA gene identity) classified as Alveolata, non-alveolate/non-photosynthetic picoeukaryotes, and photosynthetic picoeukaryotes (PPE) comprised 58%, 17%, and 8% of total picoeukaryote sequences, respectively. We observed a distinct two-layer structuring of PPE assemblages, coupled with higher alpha diversity in the well-lit, low-nutrient (<75 m) compared to the dimly lit, potentially higher-nutrient (100-175 m) regions of the euphotic zone. During winter and spring mixing periods, specific PPE assemblages in the lower euphotic zone (Pelagophyceae, Mamiellophyceae, Prymnesiophyceae) proliferated in the upper euphotic zone, greatly influencing alpha diversity. Such results indicate that monitoring diversity metrics may reveal plankton response to environmental changes, with subsequent influences on food web dynamics and organic matter cycling. Furthermore, our results suggest that nutrient availability may promote diversity to a greater extent than competition for light, providing insights into processes shaping distributions and diversity of picoplankton in the NPSG.
Rii, Y. M., University of Hawaii/C-MORE, USA, firstname.lastname@example.org
Lindh, M. V., Center for Microbial Oceanography: Research and Education, USA, email@example.com
Church, M. J., University of Montana, USA, firstname.lastname@example.org
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