Major
Marine Biology
Advisor
Robinson, Rebecca S
Advisor Department
Oceanography, Graduate School of
Advisor
Kelly, Roger
Advisor Department
Oceanography, Graduate School of
Date
4-2018
Keywords
Iodine/Calcium ratios; oxygen levels; past climate
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Abstract
ANGELA STAHL (Marine Biology)
Iodine to Calcium Ratios in Marine Carbonates as an Indicator of Oxygen Levels
Sponsor: Rebecca Robinson (Graduate School of Oceanography)
The Earth goes through natural cycles of warm and cool periods. In the past,
warmer oceans during interglacial periods have been shown to hold less oxygen
in their waters compared to cooler, glacial oceans. For this research, we are
studying an area in the Eastern Tropical Pacific where it is known to have
variable concentrations of dissolved oxygen in the waters due to the influence of
the climate. Oxygen is a vital component for most organisms to function, even
in the ocean. Organisms take up dissolved oxygen from the water and use it for
respiration, which produces energy for the organisms.
The organisms focused on for this research are marine microorganisms called
foraminifera, which form calcium carbonate shells. These organisms take up
carbonate ions (CO32-) and calcium ions (Ca2+) and combine the two to make
hard calcium carbonate (CaCO3) shells. These foraminifera have been shown
to use iodate in an ionic substitution for the carbonate ion in their shells when
iodate is present in seawater. Iodate concentration directly varies with oxygen
concentration in seawater. By measuring the iodine to calcium ratio in the
fossilized shells of these marine microorganisms, scientists can estimate how
much oxygen was in the ocean during these glacial-interglacial cycles of the past.
To measure the iodine to calcium ratio of the shells, the microfossils are crushed,
stripped from any surface contamination, dissolved in acid, and measured using
an inductively coupled plasma mass spectrometer, ICP-MS. I am measuring the
iodine to calcium ratios in microfossils that range in age from 1,000 to 120,000
years.
With climate change raising global temperatures of the atmosphere and the
ocean, measuring the oxygen levels of a warmer past could possibly give us an
idea of what to expect in the future. Learning how organisms function during
these warmer, lower oxygen periods could show us what could happen in the
near future if we do not actively try to reduce our carbon emissions and slow
human-induced climate change.