238 Recent Advances and New Voices in Marine and Coastal Geoscience

We seek abstracts on physical oceanography, marine geology, geomorphology, sediment transport, geophysics, tectonic processes, climate change, paleobiology, or any aspect of oceans and coasts, past and present. We encourage students to participate in this session.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 213AB

Identifying Trace Metal Sources to the Australian-Antarctic Ridge Phytoplankton Bloom During a Suspected Hydrothermal Eruption

Paper number: 238-15
Program: Technical Sessions
Time: 11:45 AM – 12:00 PM

Authors

  • Hope Jerris Presenting Author
    Middlebury College, Middlebury, Vermont
  • Pamela Barrett
    Cooperative Institute for Climate, Oceans, and Ecosystem Studies, University of Washington and NOAA-PMEL, Seattle, Washington
  • Tamara Baumberger
    Cooperative Institute for Marine Resources Studies, Oregon State University and NOAA-PMEL, Hatfield Marine Science Center, Newport, Oregon
  • Patrick Monreal
    University of Washington, Seattle, Washington
  • Jessalyn Davis
    University of Washington, Seattle, Washington
  • Casey Schine
    Middlebury College, Middlebury, Vermont
  • Kevin Arrigo
    Stanford University, Stanford, California
  • Randelle Bundy
    University of Washington, Seattle, Washington
  • Joseph Resing
    University of Washington, Seattle, Washington

Abstract

The Southern Ocean is the largest of three significant high-nutrient, low-chlorophyll regions, where primary production is limited by low inputs of iron, impacting the strength of the biological carbon pump and the base of the ecosystem food web. Despite the generally limited productivity in much of the Southern Ocean, there are large, anomalous phytoplankton blooms that occur, including the annual phytoplankton bloom over the Australian-Antarctic Ridge (AAR). The primary iron sources to this bloom have yet to be defined, but some initial evidence suggests hydrothermal origins. In austral summer 2024-25, the Bloom Raiders cruise investigated hydrothermal activity along the AAR, thought to supply iron and other potentially limiting trace metals such as manganese to the water column. Seawater samples were analyzed for dissolved iron and manganese using flow injection analysis and for methane using gas chromatography. Enrichments in iron, manganese, and methane in many profiles suggest an eruption event along the AAR near 158°E during the sampling period. Iron reached elevated levels in the mixed layer, indicating the ability of a thick volcanic plume to supply trace metals throughout the water column, serving as a source of macronutrients to phytoplankton in the euphotic zone. Defining and quantifying the trace metal sources to this region aids in understanding the predictability of the AAR phytoplankton bloom, which serves as a significant feeding ground for higher trophic level organisms, including humpback whales. Defining and quantifying the trace metal sources to this region aids in understanding the predictability of the AAR phytoplankton bloom, which serves as an important natural analogue to proposed iron fertilization marine carbon dioxide removal approaches.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412202

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