Project: Collaborative Research: The Effect of Ocean Acidification on Fe Availability to Phytoplankton in Coastal and Oceanic Waters of the Eastern North Pacific

NSF Award Abstract:
Iron is an important nutrient for algae in the ocean. Different forms of iron and their availability to algae are influenced by many factors including the acidity of seawater (or pH). This research project focuses on understanding the effects of ocean acidification (low pH) on the associations between iron and chemical substances that bind with iron in seawater. The investigators will work in coastal and oceanic waters of the Pacific Ocean. These waters are characterized by substances that have weak and strong associations with iron. Samples will be collected from coastal waters off Washington State, the northern edge of the North Pacific gyre, and Ocean Station PAPA in the northeast subarctic Pacific. Water samples will be collected to test phytoplankton responses to light, pH, forms of iron, and the composition of the substances that bind with iron. This project will support graduate and undergraduate students. The investigators will participate in a range of education and outreach activities.

This study addresses oceanic responses to rising anthropogenic CO2 and is broadly relevant to ocean biogeochemistry. The investigators will study the role of ocean acidification on iron availability in the Eastern North Pacific Ocean. The study location is characterized as a high nutrient low chlorophyll (HNLC) region of the ocean, where phytoplankton may be particularly sensitive to iron availability. The study region is also characterized by gradients in ligand composition and binding strength. This study will investigate how the associations between iron and different ligands (organic compounds that bind with iron) are influenced by pH and how this, in turn, influences primary production and microbial community structure in the ocean. The investigators will use batch cultures, at pH 8.1 and 7.6, and under high and low light regimes, to examine the iron demand of phytoplankton. Understanding how pH influences iron and its relationship with ligands will provide important information for assessing the impacts of ocean acidification on primary production and biogeochemical processes.