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High bacterivory by the smallest phytoplankton in the North Atlantic Ocean

High bacterivory by the smallest phytoplankton in the North Atlantic Ocean
High bacterivory by the smallest phytoplankton in the North Atlantic Ocean
Planktonic algae <5 m in size are major fixers of inorganic carbon in the ocean1. They dominate phytoplankton biomass in post-bloom, stratified oceanic temperate waters2. Traditionally, large and small algae are viewed as having a critical growth dependence on inorganic nutrients, which the latter can better acquire at lower ambient concentrations owing to their higher surface area to volume ratios3, 4. Nonetheless, recent phosphate tracer experiments in the oligotrophic ocean5 have suggested that small algae obtain inorganic phosphate indirectly, possibly through feeding on bacterioplankton. There have been numerous microscopy-based studies of algae feeding mixotrophically6, 7 in the laboratory8, 9, 10 and field11, 12, 13, 14, as well as mathematical modelling of the ecological importance of mixotrophy15. However, because of methodological limitations16 there has not been a direct comparison of obligate heterotrophic and mixotrophic bacterivory. Here we present direct evidence that small algae carry out 40–95% of the bacterivory in the euphotic layer of the temperate North Atlantic Ocean in summer. A similar range of 37–70% was determined in the surface waters of the tropical North-East Atlantic Ocean, suggesting the global significance of mixotrophy. This finding reveals that even the smallest algae have less dependence on dissolved inorganic nutrients than previously thought, obtaining a quarter of their biomass from bacterivory. This has important implications for how we perceive nutrient acquisition and limitation of carbon-fixing protists as well as control of bacterioplankton in the ocean.
0028-0836
224-226
Zubkov, Mikhail V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Tarran, Glen A.
218a9233-a6ae-4d0c-a9ca-35ad0d5a35f7
Zubkov, Mikhail V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Tarran, Glen A.
218a9233-a6ae-4d0c-a9ca-35ad0d5a35f7

Zubkov, Mikhail V. and Tarran, Glen A. (2008) High bacterivory by the smallest phytoplankton in the North Atlantic Ocean. Nature, 455 (7210), 224-226. (doi:10.1038/nature07236).

Record type: Article

Abstract

Planktonic algae <5 m in size are major fixers of inorganic carbon in the ocean1. They dominate phytoplankton biomass in post-bloom, stratified oceanic temperate waters2. Traditionally, large and small algae are viewed as having a critical growth dependence on inorganic nutrients, which the latter can better acquire at lower ambient concentrations owing to their higher surface area to volume ratios3, 4. Nonetheless, recent phosphate tracer experiments in the oligotrophic ocean5 have suggested that small algae obtain inorganic phosphate indirectly, possibly through feeding on bacterioplankton. There have been numerous microscopy-based studies of algae feeding mixotrophically6, 7 in the laboratory8, 9, 10 and field11, 12, 13, 14, as well as mathematical modelling of the ecological importance of mixotrophy15. However, because of methodological limitations16 there has not been a direct comparison of obligate heterotrophic and mixotrophic bacterivory. Here we present direct evidence that small algae carry out 40–95% of the bacterivory in the euphotic layer of the temperate North Atlantic Ocean in summer. A similar range of 37–70% was determined in the surface waters of the tropical North-East Atlantic Ocean, suggesting the global significance of mixotrophy. This finding reveals that even the smallest algae have less dependence on dissolved inorganic nutrients than previously thought, obtaining a quarter of their biomass from bacterivory. This has important implications for how we perceive nutrient acquisition and limitation of carbon-fixing protists as well as control of bacterioplankton in the ocean.

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Published date: 11 September 2008
Organisations: National Oceanography Centre,Southampton

Identifiers

Local EPrints ID: 52554
URI: http://eprints.soton.ac.uk/id/eprint/52554
ISSN: 0028-0836
PURE UUID: e498e61d-5899-4732-b7dd-965db59de3d3

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Date deposited: 09 Jul 2008
Last modified: 15 Mar 2024 10:37

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Contributors

Author: Mikhail V. Zubkov
Author: Glen A. Tarran

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