Intraspecific variability in Phaeocystis antarctica's response to iron and light stress

• Main Authors: Luxem, Katja E., Ellwood, Michael J., Strzepek, Robert F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Public Library of Science 2017
• Subjects: Southern Ocean; Antarc*; Antarctica
• Online Access: https://doi.org/10.1371/journal.pone.0179751; https://www.ncbi.nlm.nih.gov/pmc/PMC5503234

Phaeocystis antarctica is an abundant phytoplankton species in the Southern Ocean, where growth is frequently limited by iron and light. Being able to grow under low iron conditions is essential to the species' success, but there have been hints that this ability differs among clones. Here, we compare the growth, cell size and chlorophyll a concentrations of four P. antarctica clones cultured under different iron and light conditions. Iron was provided either as unchelated iron (Fe′) or bound to the bacterial siderophore desferrioxamine B, representing, respectively, the most and least bioavailable forms of iron which phytoplankton encounter in the marine environment. The growth rate data demonstrate that the clones vary in their ability to grow using organically bound iron, and that this ability is not related to their ability to grow at low inorganic iron concentrations. These results are consistent at low and high light. Physiologically, only three of the four clones shrink or decrease the concentration of chlorophyll a in response to iron limitation, and only one clone decreases colony formation. Together, our data show that P. antarctica clones 1) respond to the same degree of iron limitation using different acclimation strategies, and 2) vary in their ability to grow under the same external iron and light conditions. This physiological diversity is surprisingly large for isolates of a single phytoplankton species. © 2017 Luxem et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: November 27, 2016; Accepted: June 2, 2017; Published: July 10, 2017. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. KEL was supported by the Robert and Delpha Noland Summer Internship, which funded her travel to and accommodation in Australia. The Australian Research ...