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Microfossils help monitor when deep-sea methane deposits convert to gas and rise to the seafloor.
A team of scientists led by a Brown University researcher has developed a new method for monitoring when deep-sea methane deposits convert to gas and rise toward the seafloor in previously too small amounts to detect.
Ice worms inhabiting methane hydrate. Photo credit: NOAA
The U.S. National Science Foundation-supported research, published in Earth and Planetary Science Letters, shows that fossils of single-cell organisms called benthic foraminifera in the order Miliolida have a unique ability to serve as resources.
These organisms can record the location and the timing of when crystalized methane goes through a process known as methane hydrate dissociation when ice-like methane found beneath the seafloor transforms into gas and rises upward.
The researchers have shown through an analysis of 372 Miliolida fossils that these previously unrecorded dissociation events have occurred in the Bay of Bengal in the northern Indian Ocean for the past 1.5 million years, but they were too small to detect through other signs of hydrate dissociation.
The analysis shows the dissociation events have been largely driven by increasingly warming waters in the region.
Miliolida foraminifera — Pyrgo spp., Quinqueloculina spp., and Spiroloculina spp. — are have the unique ability to sense small-scale methane dissociation events. The image is an adaptation from a figure in the paper.
The findings underscore climate change’s effects on ancient methane deposits and show that the hydrates transition from their solid ice-like phase to gas more often than scientists thought.
“If you look at other sites around the area we studied, the records show only two methane dissociation events in the last million years,” said Steven Clemens, lead author of the study.
“Here, we see it pretty much everywhere we look, particularly when Earth’s climate was warm. It’s clear that methane is cycling much more rapidly and often between its ice and dissolved phases than we could previously detect.”
Ocean – illustrative photo. Image credit: Alexander Hafemann via Unsplash, free license
The researchers said the study is the first to document three Miliolida foraminifera species — Pyrgo spp., Quinqueloculina spp. and Spiroloculina spp. — are sensing small-scale dissociation events.
Analysis of other types of foraminifera the scientists collected during a previous expedition to the Indian Ocean showed that unlike Miliolida, they do not detect these smaller-scale dissociation events.
Source: NSF
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