Mucospheres produced by a mixotrophic protist impact ocean carbon cycling

Michaela E. Larsson*, Anna R. Bramucci, Sinead Collins, Gustaaf Hallegraeff, Tim Kahlke, Jean Baptiste Raina, Justin R. Seymour, Martina A. Doblin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Mixotrophic protists (unicellular eukaryotes) that engage in both phototrophy (photosynthesis) and phago-heterotrophy (engulfment of particles)—are predicted to contribute substantially to energy fluxes and marine biogeochemical cycles. However, their impact remains largely unquantified. Here we describe the sophisticated foraging strategy of a widespread mixotrophic dinoflagellate, involving the production of carbon-rich ‘mucospheres’ that attract, capture, and immobilise microbial prey facilitating their consumption. We provide a detailed characterisation of this previously undescribed behaviour and reveal that it represents an overlooked, yet quantitatively significant mechanism for oceanic carbon fluxes. Following feeding, the mucospheres laden with surplus prey are discarded and sink, contributing an estimated 0.17–1.24 mg m−2 d−1 of particulate organic carbon, or 0.02–0.15 Gt to the biological pump annually, which represents 0.1–0.7% of the estimated total export from the euphotic zone. These findings demonstrate how the complex foraging behaviour of a single species of mixotrophic protist can disproportionally contribute to the vertical flux of carbon in the ocean.

Original languageEnglish
Article number1301
Number of pages15
JournalNature Communications
Volume13
Issue number1
Early online date14 Mar 2022
DOIs
Publication statusE-pub ahead of print - 14 Mar 2022

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