IMPACT OF LAKE BROWNING ON PHYTOPLANKTON-BACTERIAL INTERACTIONS: MEDIATED BY BACTERIAL B12 PRODUCTION

Lake browning, driven by elevated inputs of dissolved organic matter (DOM), is altering lake physicochemical environments and reshaping phytoplankton compositions. In this study, we investigated vitamin B12 -mediated interactions between phytoplankton and bacterial communities in lakes with low and high DOC concentration. Over 50% of phytoplankton species depend on B12, which is produced by a limited group of bacteria, and thus changes in bacterial community, due to rising DOC levels in brown lakes, may decrease the abundance of B12 auxotrophic algae. We used genetic marker of 18S V4 region for identifying eukaryotic plankton composition, rbcL for diatom, and 16S rRNA V4 region for bacteria to discover the correlations between bacterial and fungal communities in lakes with different DOC levels.  We hypothesise that: (1) DOC promotes the growth of B12-consuming bacteria, reducing the abundance of B12-producing bacteria in brown lakes; and (2) the phytoplankton community may shift from diatom dominated in clear lakes to mixotrophic dominated in brown lakes that may due to competition for B12 with B12-consuming bacteria. Our findings emphasize the impact of lake browning on bacteria-alga interactions, mediated by changes of B12-producing bacteria.

Presentation Preference: Oral

Primary Presenter: Xuan Zhou, University of Eastern Finland (xuan.zhou@uef.fi)

Authors:

Sadikshya Ghimire, University of Eastern Finland  (sadikshya.ghimire@uef.fi)

Xuan Zhou, University of Eastern Finland  (xuan.zhou@uef.fi)

Mohammadsalar Sohrabi, University of Eastern Finland  (salar.sohrabi@uef.fi)

Ursula Strandberg, University of Eastern Finland  (ursula.strandberg@uef.fi)