Diversity and productivity of photosynthetic picoeukaryotes in biogeochemically distinct regions of the South East Pacific Ocean. (8th January 2016)

• Record Type: Journal Article
• Authors: Rii, Yoshimi M.; Duhamel, Solange; Bidigare, Robert R.; Karl, David M.; Repeta, Daniel J.; Church, Matthew J.
• Is Part Of: Limnology and oceanography. Volume 61:Number 3(2016)
• Page Start: 806
• Page End: 824
• Publication Date: 2016-01-08
• Subjects: Limnology -- Periodicals; Oceanography -- Periodicals; Océanographie; Limnologie; Limnology; Oceanography; Computer network resources; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); Periodicals; 551.4805
• DOI: 10.1002/lno.10255
• Languages: English
• ISSNs: 0024-3590

Abstract

Abstract: Picophytoplankton, including photosynthetic picoeukaryotes (PPE) and unicellular cyanobacteria, are important contributors to plankton biomass and primary productivity. In this study, phytoplankton composition and rates of carbon fixation were examined across a large trophic gradient in the South East Pacific Ocean (SEP) using a suite of approaches: photosynthetic pigments, rates of 14 C‐primary productivity, and phylogenetic analyses of partial 18S rRNA genes PCR amplified and sequenced from flow cytometrically sorted cells. While phytoplankton >10 μm (diatoms and dinoflagellates) were prevalent in the upwelling region off the Chilean coast, picophytoplankton consistently accounted for 55–92% of the total chlorophyll a inventories and >60% of 14 C‐primary productivity throughout the sampling region. Estimates of rates of 14 C‐primary productivity derived from flow cytometric sorting of radiolabeled cells revealed that the contributions of PPE and Prochlorococcus to euphotic zone depth‐integrated picoplankton productivity were nearly equivalent (ranging 36–57%) along the transect, with PPE comprising a larger share of picoplankton productivity than cyanobacteria in the well‐lit (>15% surface irradiance) region compared with in the lower regions (1–7% surface irradiance) of the euphotic zone. 18S rRNA gene sequence analyses revealed the taxonomic identities of PPE; e.g., Mamiellophyceae ( Ostreococcus ) were the dominant PPE in the upwelling‐influenced waters, while members of the Chrysophyceae, Prymnesiophyceae, Pelagophyceae, and Prasinophyceae Clades VII and IX flourished in the oligotrophic South Pacific Subtropical Gyre. Our results suggest that, despite low numerical abundance in comparison to cyanobacteria, diverse members of PPE are significant contributors to carbon cycling across biogeochemically distinct regions of the SEP.