Bubble Hitchhikers Could Check Greenhouse Gas
Methane gas bubbles rise from the seafloor. These bubbles were originally noticed by NOAA Ship
Oct. 23, 2012 --
For 37 years the Nikon Small World photography competition showcases the beauty and extreme details captured using light microscopes. Every year the world below the waves provides many interesting subjects for the Small World competition. Most examples of aquatic life are entered by professionals in, or students of marine biology, but many of these images were provided by entrants from other disciplines who simply find marine life fascinating. Here, photomicrographer Arlene Wechezak of Anacortes, Wash., and 10th place winner of the 2009 Small World Contest, magnified 10x an Obelia species of hydrozoa with extruded medusae as a fresh sea water mount using a darkfield.
Here we see the same species as before only this time magnified 40x its original size. The extruded medusae of the Obelia hydrozoa contain tentacles that sting and capture the animal's prey.
Bruno Pernet and Russell Zimmer, California S
In this image, biologists magnified 20x a species of bryozoan of the genus Membranipora found on seaweed and kelp using stereomicroscopy.
James H. Nicholson, Hanian Lang, and Sylvia G
Almost transparent tissue covers the hard skeleton "cups" of each polyp in this brightfield photo of brain coral in the genus Goniastrea magnified 25x.
Marine biologist Alvaro Migotto of the University of São Paulo in Brazil used stereomicroscopy and a darkfield to capture this photo of a brittle star magnified 8x.
Photographer David Maitland of Feltwell, UK, zoomed in with 100x magnification on coral sand over a brightfield.
Tomasz Kozielec, Nicolaus Copernicus Universi
Surface of shark skin tanned with a chromium compound magnified 40x with reflected light.
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John Dolan, CNRS/University of Paris Laborato
On its side this marine ciliate (Rhabdonella spiralis)looks like a trumpet; when the image is turned vertical it looks like a champagne flute - a fine photo from French oceanographer John Dolan, who used a differential interference contrast technique and 40x magnification.
Robert Brons Insula College Dordrecht in Spij
A freshwater Bryozoan, or moss animal, Cristatella mucedo in a darkfield magnified 6.5x.
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Biologist Diana Lipscomb of George Washington University in Washington, used Nomarski Interference Contrast and a magnification of 400x the original size to showcase a suctorian ciliate, Acineta tuberosa, in the phylum Ciliophora.
Using Nomarski Interference Contrast and a magnification of 400x the original size this photo shows a ciliate in the genus Sonderia that preys upon various algae, diatoms, and cyanobacteria.
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Seafloor-dwelling bacteria may hitch a ride on methane bubbles seeping from deep-sea vents, preventing the methane from reaching the atmosphere by eating it up, new research suggests.
The findings, presented here today (Dec. 9) at the annual meeting of the American Geophysical Union, could help explain how such huge amounts of the greenhouse gas methane are belched from the ocean floor, yet somehow never reach the atmosphere.
"Above these methane seeps, you have these bubbles released from the sediment and you can see a higher abundance of these microbes in the water column," said study co-author Oliver Schmale, a geologist and marine chemist at the Leibniz Institute for Baltic Sea Research in Germany. "The microbes consume methane from these seeps before it escapes into the atmosphere." [Earth in the Balance: 7 Crucial Tipping Points]
Methane is a potent greenhouse gas, and huge reserves of it are buried beneath the oceans. Many scientists worry that if the oceans warm enough, these huge troves of methane could be released from their deep-sea storage and released into the atmosphere, fueling a huge spike in temperatures.
While much of the methane is locked in an inactive form, at shallower depths, bubbles of methane naturally seep up from mud volcanoes and other cracks in the ocean floor. Yet somehow, very little of this methane reaches the atmosphere.
Schmale and his colleagues proposed that bacteria living in the water column traveled on the bubbles, breaking down the methane before it had a chance to reach the surface. To test that idea, a team of scuba divers placed a device that collected tiny bubbles of methane as they floated from an oil and gas exploration field off the shore of Santa Barbara, Calif. The bubble catcher trapped the gas bubbles in a cylinder full of ultra-pure water. The gas bubbles rose to the top of the tube, while the particles attached to them stayed in the water. As a control, the researchers did the same experiment, but trapped artificial bubbles that weren't in contact with the seafloor.
The team then flushed out the water and collected the particles that remained on a filter. They then looked for gene signatures of methane-munching bacteria and archaea (single-celled organisms that make up one of life's kingdoms).
The team found that about 160 methane-oxidizing bacteria hitched a ride on the outside of each bubble, munching on the methane as they traveled. Each bubble also carried over 44,000 cells of other types. By contrast, the control bubbles didn't contain these organisms.
The new findings could help explain how large amounts of methane are broken down before reaching the ocean's surface. The bubble bacterial elevator could also mean that the ocean could have a built-in mechanism to deal with large releases of methane.
"If you have a direct injection of these microbes into the affected water column, you have a direct sink," Schmale told LiveScience.
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