Divergent physiological and molecular responses of light‐ and iron‐limited Southern Ocean phytoplankton

• Published in: Limnology and Oceanography Letters
• Main Authors: Andrew, Sarah M., Strzepek, Robert F., M. Whitney, Spencer, Chow, Wah Soon, Ellwood, Michael J.
• Other Authors: Australian Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Southern Ocean
• Online Access: http://dx.doi.org/10.1002/lol2.10223; https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10223; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/lol2.10223; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10223

Abstract It has recently been shown that Southern Ocean phytoplankton species have evolved to optimize their light‐harvesting potential without increasing the high iron‐requiring proteins used for photosynthesis. We measured molecular and physiological responses of phytoplankton cultures under a combination of iron and light conditions. While iron‐replete cultures mostly increased biovolume, photochemical efficiency ( F v / F m ) and the relative abundance of photosystem II (PSII) and Cytochrome b 6 f protein compared to iron‐limited cultures, light also regulated cellular chlorophyll a content and played a role in controlling PSII protein abundance. Investment of protein resources into the carbon fixing enzyme Ribulose 1,5‐bisphosphate carboxylase oxygenase (Rubisco) was species‐specific, but increased growth rates correlated with increased investment into Rubisco for all species. Our results suggest that Proboscia inermis uses a divergent molecular strategy to compete for nutrients, light, and CO 2 in the Southern Ocean.