Award: OCE-1756860

A primary goal of this award was to test the impact of ocean acidification on iron bioavailability to natural diatom communities, motivated by the need to explore the real-world implications of iron uptake mechanisms described in recent publications based on laboratory cultures. Upwelling regions of coastal California were targeted as areas where ocean acidification, iron limitation, and abundant diatom populations are known to naturally coincide. To evaluate potential impacts of acidification on phytoplankton in an upwelling region, climate change-enhanced levels of ocean acidification were simulated with natural phytoplankton communities in the California Current System during an August 2019 cruise with the California Current Ecosystem Long Term Ecological Research program. These experiments enabled probing of mixed phytoplankton assemblages’ sensitivity to short-term acidification exposure from the whole community to species-specific levels while considering iron bioavailability. Results suggest that short-term ocean acidification can impact phytoplankton iron physiology at a molecular level, possibly leading to iron stress over the longer term in natural systems. Additional publications from this grant have studied the potential influence of ocean acidification and hypoxia in nearshore areas as a result of upwelling; and the occurrence and biogeochemical impact of iron limitation in upwelling filaments. This award supported the education of several graduate students, providing valuable training towards their PhD degrees. Last Modified: 06/29/2023 Submitted by: Katherine Barbeau