Refining the ocean's thermometer

The shells of plankton called foraminifera are a record of past ocean chemistry and therefore past climate. New work led by UC Davis and OSU scientists shows that mysterious bands of magnesium in the shells of foraminifera are caused by daily day/night cycles, helping to better define this model for measuring past climate. Credit: Jennifer Fehrenbacher, OSU

Chronicling Earth's past temperature swings is a basic part of understanding climate change. One of the best records of past ocean temperatures can be found in the shells of marine creatures called foraminifera.

Known as “forams” for short, these single-celled plankton build microscopic calcite shells. When forams die, their shells fall to the ocean floor and accumulate in sediments that provide a record of past climate. The surface-feeding plankton are natural thermometers because the chemical makeup of foram shells is linked to the environmental conditions they grow in. For example, the levels of magnesium in foram shells reflect the seawater temperature in which they lived.

Ideally, forams would act as “perfect chemists” by incorporating magnesium and calcium according to well-understood chemical relationships, said study co-author Ann Russell, a researcher in paleoceanography at UC Davis. But many foram shells have alternating bands of high and low magnesium levels within their calcite shells that cannot be explained by temperature alone. These bands are only a few microns wide.

“We need to have confidence that we understand the causes of variability and the mechanisms of biological control over magnesium, and as much as we can about how the shells form,” Russell said.

Light/Dark Cycles Drive Magnesium Bands

Recent experiments led by UC Davis scientists show magnesium levels vary in foram shells due to different growth rates during daily light/dark cycles. The findings were published May 15 in the journal Nature Communications.

Earlier research at UC Davis and elsewhere had already hinted that changing sunlight levels influence shell chemistry. To investigate this idea, the research team grew foraminifera in controlled light conditions and then analyzed the shells. The team directly measured the levels of magnesium and other trace elements in the shells with high-resolution imaging techniques called laser ablation ICP-MS and NanoSIMS image mapping.

“These are amazing techniques for understanding how growth conditions affect shell geochemistry,” said lead study author Jennifer Fehrenbacher, an assistant professor of tracer oceanography at Oregon State University. Fehrenbacher led the research while she was a postdoctoral fellow at UC Davis.

The results will help increase confidence in plankton as climate records, the researchers said.

“Understanding foraminifera growth patterns is essential for understanding the mechanisms responsible for their shell chemistry and for properly interpreting past temperature records,” Fehrenbacher said.

###

The team included Professor Howard Spero and graduate student Catherine Davis from UC Davis, Alexander Gagnon at the University of Washington and John Cliff and Zihua Zhu at the U.S. Department of Energy's Pacific Northwest National Laboratory, and Pamela Martin. The work was supported by the National Science Foundation and the Department of Energy.

Media Contact

Andy Fell
ahfell@ucdavis.edu
530-752-4533

 @ucdavisnews

http://www.ucdavis.edu 

Media Contact

Andy Fell EurekAlert!

All latest news from the category: Earth Sciences

Earth Sciences (also referred to as Geosciences), which deals with basic issues surrounding our planet, plays a vital role in the area of energy and raw materials supply.

Earth Sciences comprises subjects such as geology, geography, geological informatics, paleontology, mineralogy, petrography, crystallography, geophysics, geodesy, glaciology, cartography, photogrammetry, meteorology and seismology, early-warning systems, earthquake research and polar research.

Back to home

Comments (0)

Write a comment

Newest articles

EEG ad tDCS chould serve as the basis of therapeutic strategies to combat newrological disorders. Image Credit: Institute of Science Tokyo

Using Electroencephalography to Improve Language Disorder Treatments

Researchers work towards an inexpensive and portable solution for treating aphasia  Electroencephalography (EEG) may offer a more accessible alternative to functional magnetic resonance imaging (fMRI) for guiding transcranial direct current…

The BioSCape team is poctured with NASA and South African aircraft. Image Credit: Jeremey Shelton/Fishwater Films

Measuring Life on Earth from Space: A Global Research Project

Measurements and data collected from space can be used to better understand life on Earth. An ambitious, multinational research project funded by NASA and co-led by UC Merced civil and…

NEJM study finds patients with blockages in medium-sized vessels in the brain who had endovascular treatment did not do any better and did not see any improvement compared to patients who had the standard of care. Dr. Michael Hill, MD, Dr. Mayank Goyal, MD, PhD (right). Image Credit: Riley Brandt, University of Calgary

Best Approach for Stroke in Medium-Sized Blood Vessels Identified

Calgary’s Stroke Program advancing science to improve care, treatment and outcomes for patients  University of Calgary’s Hotchkiss Brain Institute researchers with the Calgary Stroke Program at Foothills Medical Centre revolutionized…