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Turbulence simultaneously stimulates small- and large-scale CO₂ sequestration by chain-forming diatoms in the sea.

ABSTRACT: Chain-forming diatoms are key CO₂-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO₂ assimilation and large-scale biogeochemical C and N cycles in the ocean.

SUBMITTER: Bergkvist J

PROVIDER: S-EPMC6076325 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Turbulence simultaneously stimulates small- and large-scale CO<sub>2</sub> sequestration by chain-forming diatoms in the sea.

Bergkvist Johanna J Klawonn Isabell I Whitehouse Martin J MJ Lavik Gaute G Brüchert Volker V Ploug Helle H

Nature communications 20180803 1

Chain-forming diatoms are key CO<sub>2</sub>-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate ...[more]

PMID: 30076288

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Project description:The main goal of the present work is to test the hypothesis that small-scale turbulence affected physiological activities and the morphology of cyanobacteria in high turbulence environments. Using quantified turbulence in a stirring device, we conducted one set of experiments on cultures of two strains of cyanobacteria with different phenotypes; i.e., unicellular Microcystis flos-aquae and colonial Anabaena flos-aquae. The effect of small-scale turbulence examined varied from 0 to 8.01×10-2 m2s-3, covering the range of turbulence intensities experienced by cyanobacteria in the field. The results of photosynthesis activity and the cellular chlorophyll a in both strains did not change significantly among the turbulence levels, indicating that the potential indirect effects of a light regime under the gradient of turbulent mixing could be ignored. However, the experiments demonstrated that small-scale turbulence significantly modulated algal nutrient uptake and growth in comparison to the stagnant control. Cellular N and C of the two stains showed approximately the same responses, resulting in a similar pattern of C/N ratios. Moreover, the change in the phosphate uptake rate was similar to that of growth in two strains, which implied that growth characteristic responses to turbulence may be dependent on the P strategy, which was correlated with accumulation of polyphosphate. Additionally, our results also showed the filament length of A. flos-aquae decreased in response to high turbulence, which could favor enhancement of the nutrient uptake. These findings suggested that both M. flos-aquae and A. flos-aquae adjust their growth rates in response to turbulence levels in the ways of asynchronous cellular stoichiometry of C, N, and P, especially the phosphorus strategy, to improve the nutrient application efficiency. The fact that adaptation strategies of cyanobacteria diversely to turbulence depending on their physiological conditions presents a good example to understand the direct cause-effect relationship between hydrodynamic forces and algae.

Dataset Information

Turbulence simultaneously stimulates small- and large-scale CO₂ sequestration by chain-forming diatoms in the sea.

Publications

Turbulence simultaneously stimulates small- and large-scale CO<sub>2</sub> sequestration by chain-forming diatoms in the sea.

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Dataset Information

Turbulence simultaneously stimulates small- and large-scale CO2 sequestration by chain-forming diatoms in the sea.

Publications

Turbulence simultaneously stimulates small- and large-scale CO<sub>2</sub> sequestration by chain-forming diatoms in the sea.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Turbulence simultaneously stimulates small- and large-scale CO₂ sequestration by chain-forming diatoms in the sea.