Dataset Information

Nanoplanktonic diatoms are globally overlooked but play a role in spring blooms and carbon export.

ABSTRACT: Diatoms are one of the major primary producers in the ocean, responsible annually for ~20% of photosynthetically fixed CO2 on Earth. In oceanic models, they are typically represented as large (>20?µm) microphytoplankton. However, many diatoms belong to the nanophytoplankton (2-20?µm) and a few species even overlap with the picoplanktonic size-class (<2?µm). Due to their minute size and difficulty of detection they are poorly characterized. Here we describe a massive spring bloom of the smallest known diatom (Minidiscus) in the northwestern Mediterranean Sea. Analysis of Tara Oceans data, together with literature review, reveal a general oversight of the significance of these small diatoms at the global scale. We further evidence that they can reach the seafloor at high sinking rates, implying the need to revise our classical binary vision of pico- and nanoplanktonic cells fueling the microbial loop, while only microphytoplankton sustain secondary trophic levels and carbon export.

SUBMITTER: Leblanc K

PROVIDER: S-EPMC5838239 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Nanoplanktonic diatoms are globally overlooked but play a role in spring blooms and carbon export.

Leblanc Karine K Quéguiner Bernard B Diaz Frédéric F Cornet Véronique V Michel-Rodriguez Mónica M Durrieu de Madron Xavier X Bowler Chris C Malviya Shruti S Thyssen Melilotus M Grégori Gérald G Rembauville Mathieu M Grosso Olivier O Poulain Julie J de Vargas Colomban C Pujo-Pay Mireille M Conan Pascal P

Nature communications 20180305 1

Diatoms are one of the major primary producers in the ocean, responsible annually for ~20% of photosynthetically fixed CO<sub>2</sub> on Earth. In oceanic models, they are typically represented as large (>20 µm) microphytoplankton. However, many diatoms belong to the nanophytoplankton (2-20 µm) and a few species even overlap with the picoplanktonic size-class (<2 µm). Due to their minute size and difficulty of detection they are poorly characterized. Here we describe a massive spring bloom of th ...[more]

PMID: 29507291

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Project description:Labyrinthulomycetes protists are an important heterotrophic component of microeukaryotes in the world's oceans, but their distribution patterns and ecological roles are poorly understood in pelagic waters. This study employed flow cytometry and high-throughput sequencing to characterize the abundance, diversity, and community structure of Labyrinthulomycetes in the pelagic Eastern Indian Ocean. The total Labyrinthulomycetes abundance varied much more among stations than did the abundance of prokaryotic plankton, reaching over 1,000 cells mL-1 at a few "bloom" stations. The total Labyrinthulomycetes abundance did not decline with depth throughout the whole water column (5 to 2,000 m) like the abundance of prokaryotic plankton did, and the Labyrinthulomycetes average projected biomass over all samples was higher than that of the prokaryotic plankton. However, Labyrinthulomycetes diversity showed obvious vertical variations, with richness, Shannon diversity, and evenness greatest in the upper epipelagic, lower epipelagic, and deep waters, respectively. Many abundant phylotypes were detected across multiple water layers, which aligned with the constant vertical Labyrinthulomycetes biomass, suggesting potential sinking and contribution to the biological pump. Hierarchical clustering revealed distinct ecotypes partitioning by vertical distribution patterns, suggesting their differential roles in the carbon cycle and storage processes. Particularly, most phylotypes showed patchy distributions (occurring in only few samples) as previously found in the coastal waters, but they were less associated with the Labyrinthulomycetes blooms than the prevalent phylotypes. Overall, this study revealed distinct patterns of Labyrinthulomycetes ecotypes and shed light on their importance in the pelagic ocean carbon cycling and sequestration relative to that of the prokaryotic plankton. IMPORTANCE While prokaryotic heterotrophic plankton are well accepted as major players in oceanic carbon cycling, the ecological distributions and functions of their microeukaryotic counterparts in the pelagic ocean remain largely unknown. This study focused on an important group of heterotrophic (mainly osmotrophic) protistan microbes, the Labyrinthulomycetes, whose biomass can surpass that of the prokaryotic plankton in many marine ecosystems, including the bathypelagic ocean. We found patchy horizontal but persistent vertical abundance profiles of the Labyrinthulomycetes protists in the pelagic waters of the Eastern Indian Ocean, which were distinct from the spatial patterns of the prokaryotic plankton. Moreover, multiple Labyrinthulomycetes ecotypes with distinct vertical patterns were detected and, based on the physiologic, metabolic, and genomic understanding of their cultivated relatives, were inferred to play multifaceted key roles in the carbon cycle and sequestration, particularly as contributors to the vertical carbon export from the surface to the dark ocean, i.e., the biological pump.

Dataset Information

Nanoplanktonic diatoms are globally overlooked but play a role in spring blooms and carbon export.

Publications

Nanoplanktonic diatoms are globally overlooked but play a role in spring blooms and carbon export.

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