Integrating Phytoplankton Genomics and Remote Sensing to Detect Iron Stress from Space

Iron stress is a critical factor in biological oceanography, constraining the growth of primary productivity in an estimated 60% of the global surface ocean.  Phytoplankton become iron stressed when the iron to nitrogen supply ratio is low. Conditions likely to induce iron stress in phytoplankton include low aeolian dust deposition and/ or high vertical mixing, both of which vary across time and space. However, only a few studies focus on the spatial and temporal of iron stress outside of HNLC regions. This gap limits our ability to fully assess the dynamics of global phytoplankton iron stress. The satellite-derived fluorescence quantum yield (Φ_sat), a spatial-temporal dataset spanning 20+ years derived from MODIS-Aqua, provides insight into phytoplankton iron stress through their photosynthetic physiological responses. The integration of genomics can validate Φ_sat primarily as an iron stress indicator. This validation allows us to assess the global spatial and temporal distribution of iron stress beyond the well-known HNLC regions. Thus far the derivation of the Φsat signal has been updated and reassessed using the latest 2022 reprocessed MODIS data. We integrated in-situ hydrography and genomic measurements with satellite remote sensing to quantify the global contemporary variation in iron stress. Results show that Φ_sat and in-situ genomic iron stress biomarkers have a positive correlation. Also, that Φ_sat and community Earth System Models iron stress models have a positive correlation. Our validation results indicate that Φ_sat is a measurement of iron stress. Furthermore, spatial-temporal evaluations show that Φ_sat is elevated in well-known High Nutrient Low Chlorophyll (HNLC) regions. In addition, Φ_sat is elevated seasonally in the North Atlantic spring and Indian Ocean summer. The long-term trends of Φsat show a prominent decreasing iron stress trend in gyre regions. The Φsat validation has allowed us to assess the global spatial and temporal distribution of iron stress beyond the well-known HNLC regions. 

Presentation Preference: Oral

Primary Presenter: Amy Nuno, University of California, Irvine (anunopug@uci.edu)

Authors:

Amy Nuno, Univeristy of California, Irvine  (anunopug@uci.edu)

Adam Martiny, Univeristy of California, Irvine  (amartiny@uci.edu)

Toby Westberry, Oregon State University  (westbert@oregonstate.edu)

Mike Behrenfeld, Oregon State University  (Michael.Behrenfeld@oregonstate.edu)