Modulation of the iron limitation response by silicate and light availability in Southern Ocean diatoms
Final Report Abstract
In the frame of this project I aimed at the assessment and characterization of acclimation processes present in Southern Ocean phytoplankton species towards the combination of the three most important future driving factors: iron and light availability and pCO2. Batch culture experiments were conducted with ecologically relevant phytoplankton species (Phaeocystis antarctica, Chaetoceros debilis and Fragilariopsis kerguelensis), in order to assess the effect of one or the combined effect of two driving factors on the physiology and gene expression. Not surprisingly, the species investigated exhibited individual acclimation strategies, as seen on either or both levels assessed (physiology or transcriptome). Indeed, whereas P. antarctica was not negatively affected, the two diatoms C. debilis and F. kerguelensis exhibited reduced growth and lower POC production under ocean acidification and high light, respectively. These findings went along with elevated expression of genes coding for light harvest chain proteins involved in photoprotection, underpinning the differences in the sensitivity to these conditions in the investigated diatom species. Similarly, whereas C. debilis could cope with low and medium light levels under iron limitation by exhibiting high photoprotective capacities, high light in combination with iron limitation did not allow growth. Contrastingly light availability did not affect growth under either replete or depleted iron conditions in P. antarctica suggesting again lower susceptibility towards the combination of iron limitation and high light as compared to the diatom investigated. Should climate change result in higher sea surface temperature and more pronounced stratification of the Southern Ocean, higher average light intensity and lower iron supply may be the consequences. If so, our observations suggest that the haptophyte Phaeocystis antarctica may outcompete Chaetoceros debilis in the future Southern Ocean, and possibly other species as well.
Publications
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(2017) Two Southern Ocean diatoms are more sensitive to ocean acidification and changes in irradiance than the Prymnesiophyte Phaeocystis antarctica. Physiologia Plantarum 160: 155-170
Trimborn, S, Thoms, S, Brenneis, T, Heiden, JP, Beszteri, S & Bischof, K
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(2018) The impacts of iron limitation and ocean acidification on the cellular stoichiometry, photophysiology and transcriptome of Phaeocystis antarctica. Limnology and Oceanography
Koch F, Beszteri S, Harms L & Trimborn S
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(2018) The response of three Southern Ocean phytoplankton species to ocean acidification and light availability: A transcriptomic study. Protist
Beszteri S, Thoms S, Benes V, Harms L & Trimborn S
