Award: OCE-2123303

This project was part of the 65-day research cruise (“GP17-ANT”) to the Amundsen Sea sector of the Antarctic margin in November 2023-January 2024, which was part of the International GEOTRACES Programme (www.geotraces.org), a coordinated global effort to measure the distribution of “trace elements and their isotopes” (TEIs) in the global ocean. Trace elements are any element on the periodic table that is found in very small quantities.  The trace elements measured by the GEOTRACES program include those that are essential nutrients for life in the ocean, such as iron, cobalt, and zinc, those that are contaminants and toxic, such as lead and mercury, and those that trace specific inputs, such as aluminum for inputs from land.   Isotopes are variations of elements that differ in their atomic mass, and can be stable or radioactive. 

The Amundsen Sea is the location of the fastest melting Antarctic glaciers.  This rapid glacial melt is expected to impact ocean circulation and biogeochemical cycles.  Bringing the GEOTRACES toolbox to studying this region helps to understand the influence of glacial melt on the nutrient and toxic trace elements in the region and the consequences for biological activity, and our stable and radioactive isotope tools help us to trace the source and rates of important processes in this region.

This specific project focused on characterizing the composition, scavenging efficiency and bioavailability of size-fractionated particles.  One of the most important consequences of glacial melt on the biology and chemistry of the Amundsen sea is the glacial melt-enhanced supply of the micronutrient iron to the phytoplankton community.  It has been hypothesized that this supply of iron explains why the Amundsen sea has the highest rate of photosynthesis of all the seas surrounding Antarctica.  Prediction of how the effects of increasing iron supply may evolve into the future depends critically on understanding how long-lived this glacial iron is.  One of the main processes that removes dissolved iron from seawater is called scavenging, in which trace elements such as iron stick (“adsorb”) onto marine particles, which are then removed from the water column when the particles sink to the seafloor.  Scavenging depends critically on the concentration and composition of marine particles—the higher the concentration, the more efficiently trace metals are removed. Some types are particles are more efficient at removing trace metals than others.  This project provided the first ever distribution of marine particle concentration and composition in the Amundsen Sea.  Our particle data can now be used to constrain models that predict whether glacial iron can enhance photosynthesis in the broader Southern Ocean, where it could be globally significant. 

We also characterized the chemical and mineralogical forms of particulate iron that are enhanced by glacial meltwater, and tested their bioavailability to Antarctic phytoplankton.  We find that iron-containing particles in the Amundsen sea are indeed bioavailable to the phytoplankton communities there, suggesting that both the dissolved and particulate forms of iron that have been shown to be enhanced by glacial meltwater have important biological consequences.

This projected supported a wide range of young scientists ranging from four high school students still deciding what to study in college, two UCSC undergraduate students majoring in Marine Biology and Environmental Science, deciding what they want to do after college, two UCSC graduate students in the Ocean Sciences department, creating new knowledge in oceanography, and 1 PhD-level project scientist, pushing the state of the art in analytical methods.  All of them worked directly with samples we brought back from Antarctica, connecting them to this globally important region.

 

 

 

Last Modified: 05/16/2026
Modified by: Phoebe J Lam