MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12389

Physiological stress response associated with elevated CO2 and dissolved iron in a phytoplankton community dominated by the coccolithophore Emiliania huxleyi

María Segovia*, M Rosario Lorenzo, Concepción Iñiguez, Candela García-Gómez‡

*Email: segovia@uma.es.

ABSTRACT: In the present work, we exposed a natural phytoplankton community to combinatorial present (390 µatm, LC) and future CO2 levels predicted for the year 2100 (900 µatm, HC), and ambient (4.5 nM, –DFB) and high (12 nM, +DFB) dissolved iron (dFe) levels, during 25 d by using mesocosms. We report on the physiological response of the community dominated by the coccolithophore Emiliania huxleyi. The community structure shifted on Day 10, leading to 2 different phases (1 and 2), before and after Day 10, respectively. We focused on the massive bloom of E. huxleyi that developed in Phase 2, in LC+DFB . In high dFe, pigments, and the photosynthetic parameters increased regarding the control (LC-DFB). Cell death was only detected during the community shift (Days 10–12) and, mostly, increased in the presence of high CO2. The accumulation of reactive oxygen species (ROS) decreased under high dFe, pointing to an efficient metabolism rather than to a stressed one. DNA lesions, caused by excess irradiance, were minimised under high Fe. E. huxleyi is known for its low Fe requirements for growth. However, we demonstrate that Fe is essential in E. huxleyi for DNA repair, reactive oxygen species (ROS) management and to keep the photosynthetic machinery optimal, warranting implications on C-cycling and future ecosystem functioning.