Coastal upwelling regions are among the most biologically productive ecosystems in the ocean but may be threatened by amplified ocean acidification from rising atmospheric CO₂. Increased acidification is hypothesized to reduce iron bioavailability for marine phytoplankton thereby expanding iron limitation and impacting primary production. Here we show from community to molecular levels that iron-stressed phytoplankton in an upwelling region respond to short-term acidification exposure with a multitude of iron uptake pathways and strategies that reduce cellular iron demand. A multi-omics approach was applied to trace metal clean incubations that introduced 1200 ppm CO₂ for up to four days_. Although variable, molecular-level responses indicate a prioritization of iron uptake pathways that are less hindered by acidification in conjunction with reductions in cellular iron utilization. Meanwhile, phytoplankton growth, nutrient uptake, and community compositions remained unchanged suggesting that these mechanisms may confer short-term resistance to acidification.  By extrapolating these short-term results, we speculate that longer-term exposure to acidification without increased iron inputs may result in increased iron stress for phytoplankton communities.

Primary Presenter: Robert Lampe, Scripps Institution of Oceanography (rlampe@ucsd.edu)

Authors:

Tyler Coale, Scripps Institution of Oceanography  ()

Kiefer Forsch, Scripps Institution of Oceanography  ()

Loay Jabre, Dalhousie University  ()

Samuel Kekuewa, Scripps Institution of Oceanography  ()

Erin Bertrand, Dalhousie University  ()

Aleš Horák, Academy of Sciences of the Czech Republic  ()

Miroslav Oborník, Scripps Institution of Oceanography  ()

Ariel Rabines, Scripps Institution of Oceanography  ()

Elden Rowland, Dalhousie University  ()

Hong Zheng, J. Craig Venter Institute  ()

Andreas Andersson, Scripps Institution of Oceanography  ()

Katherine Barbeau, Scripps Institution of Oceanography  ()

Andrew Allen, Scripps Institution of Oceanography  ()