Climate Change Cluster (C3), University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
Nat Commun. 2022 Mar 14;13(1):1301. doi: 10.1038/s41467-022-28867-8.
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 d 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.
混养原生生物（单细胞真核生物）既能进行光合作用（光合作用），又能进行吞噬异养（吞噬颗粒），预计它们将对能量通量和海洋生物地球化学循环做出重大贡献。然而，它们的影响在很大程度上仍然无法量化。在这里，我们描述了一种广泛存在的混养甲藻的复杂觅食策略，涉及产生富含碳的“粘球”，吸引、捕获和固定微生物猎物，从而促进其消耗。我们详细描述了这种以前未被描述的行为，并揭示了它是海洋碳通量的一个被忽视但具有重要定量意义的机制。摄食后，充满过剩猎物的粘球被丢弃并下沉，估计每年向海洋输送 0.17-1.24 毫克/米的颗粒有机碳，或每年向生物泵输送 0.02-0.15 亿吨，占从透光带估计总输出的 0.1-0.7%。这些发现表明，单一混养原生生物的复杂觅食行为如何不成比例地促进海洋中碳的垂直通量。
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