Preprints
https://doi.org/10.5194/bg-2021-220
https://doi.org/10.5194/bg-2021-220

  18 Aug 2021

18 Aug 2021

Review status: this preprint is currently under review for the journal BG.

Contrasting patterns of carbon cycling and DOM processing in two phytoplankton-bacteria communities

Samu Markku Elovaara1,2, Eeva Liisa Eronen-Rasimus2, Eero Jooseppi Asmala1, Tobias Tamelander1, and Hermanni Pekka Kaartokallio2 Samu Markku Elovaara et al.
  • 1Tvärminne Zoological Station, University of Helsinki, Helsinki, 00014, Finland
  • 2Finnish Environment Institute, Helsinki, 00790, Finland

Abstract. Microbial consumption of phytoplankton-derived organic carbon in the pelagic food web is an important component of the global C cycle. We studied C cycling in two phytoplankton-bacteria systems (non-axenic cultures of a dinoflagellate Apocalathium malmogiense and a cryptophyte Rhodomonas marina) in two experiments. In the first experiment we grew phytoplankton and bacteria in nutrient replete conditions and followed C processing at early exponential growth phase and at two later phases. Primary production and total community respiration were up to 4 and 7 times higher, respectively, in the A. malmogiense treatments. Based on the optical signals, accumulating dissolved organic C (DOC) was degraded more in the R. marina treatments and the rate of bacterial production to primary production was higher. Thus, the flow of C from phytoplankton to bacteria was relatively higher in R. marina treatments than in A. malmogiense treatments which was further supported by faster 14C transfer from phytoplankton to bacterial biomass. In the second experiment we investigated consumption of the phytoplankton-derived DOC by bacteria. DOC consumption and transformation, bacterial production and bacterial respiration were all higher in R. marina treatments. In both experiments A. malmogiense supported a bacterial community predominated by bacteria specialized in the utilization of less labile DOC (class Bacteroidia) whereas R. marina supported a community predominated by copiotrophic Alpha- and Gammaproteobacteria. Our findings suggest that large dinoflagellates cycle relatively more C between phytoplankton biomass and the inorganic C pool whereas small cryptophytes direct relatively more C to the microbial loop.

Samu Markku Elovaara et al.

Status: open (until 03 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-220', Anonymous Referee #1, 03 Sep 2021 reply
    • AC1: 'Reply on RC1', Samu Elovaara, 21 Sep 2021 reply
  • RC2: 'Comment on bg-2021-220', Anonymous Referee #2, 04 Sep 2021 reply
    • AC2: 'Reply on RC2', Samu Elovaara, 21 Sep 2021 reply

Samu Markku Elovaara et al.

Samu Markku Elovaara et al.

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Short summary
Dissolved organic matter (DOM) is a significant carbon pool in the marine environment. The composition of the DOM pool, as well as its interaction with microbes, is complex, yet understanding them is important for understanding global carbon cycling. This study shows that two phytoplankton species have different effects on the composition of the DOM pool and, through the DOM they produce, on the ensuing microbial community. These communities in turn have different effects on DOM composition.
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