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Planktic foraminifera test iodine to calcium ratios represent an emerging proxy method to assess subsurface seawater oxygenation states. Several core-top studies show lower planktic foraminifera I/Ca in locations with oxygen depleted subsurface waters compared to well oxygenated environments. The reasoning behind this trend is that only the oxidized species of iodine, iodate, is incorporated in foraminiferal calcite. The I/Ca of foraminiferal calcite is thought to reflect iodate contents in seawater. To test this hypothesis, we compare planktic foraminifera I/Ca ratios, obtained from plankton tows, with published and new seawater iodate concentrations from 1) the Eastern North Pacific with extensive oxygen depletion, 2) the Benguela Current System with moderately depleted oxygen concentrations, and 3) the well oxygenated North and South Atlantic. We find the lowest I/Ca ratios (0.07 µmol/mol) in planktic foraminifera retrieved from the Eastern North Pacific, and higher values for samples (up to 0.72 µmol/mol) obtained from the Benguela Current System and North and South Atlantic. The I/Ca ratios of plankton tow foraminifera from environments with well oxygenated subsurface waters, however, are an order of magnitude lower compared to core-tops from similarly well-oxygenated regions. This would suggest that planktic foraminifera gain iodine post-mortem, either when sinking through the water column, or during burial.
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Planktic foraminifera species assemblage from plankton tows in the Bering and Chukchi Seas, 2023-2024
Relative abundance of planktic foraminifera in plankton tows was determined to understand species distribution in Alaskan waters and through the Bering Strait. Dataset includes metadata (latitude, longitude, date, water depth, nominal tow depth) of vertical plankton tows from two cruises: SKQ202309T, a transit from Seward, Alaska (AK) to Nome, AK aboard the R/V Sikuliaq in June 2023 and HLY2403 in the Chukchi Sea aboard the United States Coast Guard Cutter (USCGC) Healy in October 2024. Relative species assemblage is reported for each planktic foraminifera species found in plankton tows due to the qualitative collection methods.
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- Award ID(s):
- 2303606
- PAR ID:
- 10588561
- Publisher / Repository:
- NSF Arctic Data Center
- Date Published:
- Subject(s) / Keyword(s):
- foraminifera plankton Bering Sea Chukchi Sea
- Format(s):
- Medium: X Other: text/xml
- Sponsoring Org:
- National Science Foundation
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