18 May 2022
18 May 2022
Status: this preprint is currently under review for the journal BG.

Ice nucleating properties of the sea ice diatom Fragilariopsis cylindrus and its exudates

Lukas Eickhoff1, Maddalena Bayer-Giraldi2, Naama Reicher3, Yinon Rudich3, and Thomas Koop1 Lukas Eickhoff et al.
  • 1Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
  • 2Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Bremerhaven, Germany
  • 3Department of Earth and Planetary Sciences, Weizmann Institute of Science, 76100 Rehovot, Israel

Abstract. In this study, we investigated the ice nucleation activity of the Antarctic sea ice diatom Fragilariopsis cylindrus. Diatoms are the main primary producers of organic carbon in the Southern Ocean and the Antarctic sea ice diatom F. cylindrus is one of the predominant species. This psychrophilic diatom is abundant in open waters and within sea ice, and it has developed several mechanisms to cope with the extreme conditions of its environment, for example the production of ice-binding proteins (IBP) and extracellular polymeric substances, known to alter the structure of ice. Here, we investigated the ice nucleation activity of F. cylindrus using a microfluidic device containing individual sub-nanoliter (~90 µm) droplet samples. The experimental method and a newly implemented Poisson statistics-based data evaluation procedure applicable to samples with low ice nucleating particle concentrations were validated by comparative ice nucleation experiments with well-investigated bacterial samples from Pseudomonas syringae (Snomax). The experiments reveal an increase of 7.2 °C in the ice nucleation temperatures for seawater containing F. cylindrus diatoms when compared to pure seawater. Moreover, also F. cylindrus fragments show ice-nucleation activity, while experiments with F. cylindrus ice binding protein (fcIBP) show no significant ice nucleation activity. A comparison with experimental results from other diatoms suggests a universal behaviour of polar sea ice diatoms and we provide a diatom mass-based parameterization of their ice-nucleation activity for use in models.

Lukas Eickhoff et al.

Status: open (until 24 Jul 2022)

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Lukas Eickhoff et al.

Lukas Eickhoff et al.


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Short summary
The formation of ice is an important process in Earth’s atmosphere, biosphere and cryosphere, in particular in polar regions. Our research focus was on the influence of the sea ice diatom Fragilariopsis cylindrus and of molecules produced by it upon heterogenous ice nucleation. For that purpose, we studied the freezing of tiny droplets containing diatoms in a microfluidic device. Together with previous studies, our results suggest a common freezing behaviour of various sea ice diatoms.