The role of mixotrophic protists in the biological carbon pump

By Aditee Mitra, Kevin J. Flynn, J. Burkholder, Terje Berge, A. Calbet, J. Raven, E. Granéli, P. Glibert, P. J. Hansen, D. Stoecker and 5 more. 2013

403 citations recorded by the source corpus.

The traditional view of the planktonic food web describes consumption of inorganic nutrients by photoautotrophic phytoplankton, which in turn supports zooplankton and ultimately higher trophic levels. Pathways centred on bacteria provide mechanisms for nutrient recycling. This structure lies at the foundation of most models used to explore biogeochemical cycling, functioning of the biological pump, and the impact of climate change on these processes. We suggest an alternative new paradigm, which sees the bulk of the base of this food web supported by protist plankton communities that are mixotrophic – combining phototrophy and phagotrophy within a single cell. The photoautotrophic eukaryotic plankton and their heterotrophic microzooplankton grazers dominate only during the developmental phases of ecosystems (e.g. spring bloom in temperate systems). With their flexible nutrition, mixotrophic protists dominate in more-mature systems (e.g. temperate summer, established eutrophic systems and oligotrophic systems); the more-stable water columns suggested under climate change may also be expected to favour these mixotrophs. We explore how such a predominantly mixotrophic structure affects microbial trophic dynamics and the biological pump. The mixotroph-dominated structure differs fundamentally in its flow of energy and nutrients, with a shortened and potentially more efficient chain from nutrient regeneration to primary production. Furthermore, mixotrophy enables a direct conduit for the support of primary production from bacterial production. We show how the exclusion of an explicit mixotrophic component in studies of the pelagic microbial communities leads to a failure to capture the true dynamics of the carbon flow. In order to prevent a misinterpretation of the full implications of climate change upon biogeochemical cycling and the functioning of the biological pump, we recommend inclusion of multi-nutrient mixotroph models within ecosystem studies.

Subfields: Ecology, Molecular Biology, Oceanography

View Paper: https://www.semanticscholar.org/paper/01b9784365b268f7e81078c699bca04bba5af71f

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Citations in the corpus

Mixotrophic Plankton in the Polar Seas: A Pan-Arctic Review (2018, background): “Ecosystem models that include mixotrophy indicate that this trophic mode has profound effects on biogeochemical cycling, including increasing carbon fixation, decreasing loss of dissolved organic carbon and increasing vertical carbon flux (Mitra et al., 2014; Ward and Follows, 2016).”
Zooplankton and the Ocean Carbon Cycle. (2017, background): “These roles, however, are represented simplistically in ecosystem and biogeochemical models, which can be sensitive to small changes in zooplankton physiological functions and rates (Mitra et al. 2014) and improved by adding behaviors such as food selectivity (Sailley et al.”
Proterozoic photosynthesis – a critical review (2015, background): “…in their conspicuously divergent and convergent evolutionary responses to temperature (Hongmei et al. 2005), salinity (Garcia-Pichel et al. 1998; Moisander et al. 2002), redox chemistry (Cohen et al. 1986), light intensity (Rocap et al. 2003), N-limitation/diazotrophy (Zehr and Kudela 2011),…”
Mechanisms of Microbial Carbon Sequestration in the Ocean - Future Research Directions (2014, background): “10 Given the vast abundance and diversity of microbes (ranging from auto- and heterotrophic prokaryotes through to photoauto-, mixo- and phagohetero- trophic protists), the complexity of microbial ecosystems and the sensitivity of microbes to environmental change, small shifts in microbial metabolic”