Invention News: From Swamp Scum To Sea Slime, UD's Tiny Environmental Probe Measures It All

March 11, 1997

NEW ORLEANS, LA.--With a tip just 25 microns in diameter, a new microelectrode sheds light on the complex natural chemistry of "swamp scum and sea slime"--including the corrosive ocean "biofilms" that damage boats, docks and off-shore platforms, a University of Delaware researcher reported today during the National Association of Corrosion Engineers (NACE) meeting.

Microelectrodes are nothing new, but most existing sensors rely on membranes that don't perform reliably in field environments, Marine Studies Prof. Stephen C. Dexter said. Also, he said, they only characterize a single gaseous compound. "Traditional devices, made of a sensitive membrane placed over an electrode, are limited mainly to measuring things like oxygen and hydrogen sulfide gases," he said, "and you would have to use separate electrodes for each gas."

By contrast, UD's microelectrode, invented by Dexter's colleague, Oceanography Prof. George W. Luther III, is hardy enough to withstand salt marshes, harbors, bays and other swampy marine settings. And, it measures key components of these environments--including dissolved oxygen, iron, manganese, hydrogen sulfide and iodide--simultaneously. Hydrogen sulfide, for example, can be detected at levels as low as one part per billion.

Luther and graduate student Paul Brendel originally developed the probe to learn more about wetland settings, where the delicate balance of nature is constantly changing because of natural chemical events such as the decomposition of organic matter. But, the work could ultimately help researchers develop more effective strategies for preventing or mitigating damage to the environment.

After all, Luther said, "If we want to understand how pollution resulting from human activities might have an impact on fresh water and marine environments, we first need to know exactly what's happening in these systems, on a day-to-day basis. The microelectrode is an extremely useful tool for gathering that information."

With graduate students Brendel and Kunming Xu, Dexter tweaked the technology to analyze thin organic biofilms on metals in seawater. Biofilms can quickly corrode metal structures, and excess metal in seawater also may endanger marine wildlife under some conditions, Dexter said.


"No one was dumb enough to stick these things in the mud before," Luther said jokingly, when asked why his rugged microelectrode wasn't invented sooner. "It's a solid-state device, and we take special steps to prevent it from fouling."

Luther invented the probe by inserting a tiny gold wire, plated with mercury, into the center of a very thin-walled glass tube just 200 microns in diameter and about four centimeters long. Undesirable chemical species were then removed by applying electrical voltages across the surface of the electrode.

After shrinking the sensor's tip to 25 microns--roughly 625 times smaller than a 1/16th-inch segment of a conventional ruler--Dexter and Xu began using Luther's invention to simultaneously measure dissolved oxygen, manganese and iron, as well as pH levels, in seawater biofilms grown on platinum and stainless steel surfaces. The sensor generated accurate measurements at 1.5-micron intervals within the biofilms, he said.

Whenever metals corrode in seawater, Dexter said, they interact with microscopic organisms and metabolic by-products--commonly known as "slime." These interactions trigger an elaborate series of reactions as microorganisms consume oxygen to produce various other chemical species. In this way, microbes may speed the corrosion of metal surfaces.

Researchers won't be able to prevent biofilms from forming on boats, docks and the ocean's surface until they know more about the chemical reactions taking place inside these films, Dexter said. That's easier said than done, because biofilms are "extremely heterogeneous, meaning that their chemistry varies from point to point within the surface," he added.

During preliminary studies of biofilms, Dexter said, "Dissolved manganese species were found in the presence and absence of oxygen, whereas iron species were only detected in anaerobic (oxygen-free) conditions within the biofilms."


Luther field-tested his microelectrode in Hawaii's Kaneohe Bay. "It's very much like a Delaware salt marsh," he said, "in that it cycles iron very rapidly." In the future, he might subject the probe to more extreme tests: in Hawaiian volcanoes and hydrothermal vents, which are loaded with gases such as hydrogen sulfide and methane, as well as iron and other metals. If the probe can withstand Hawaii's low-oxygen hydrothermal vents, he said, "it could probably go just about anywhere." Even, he said, on a deep-sea lander, where it would travel to the ocean floor. Someday, it might be possible to measure chemical species using the microelectrode by remote-control, from on board a ship, Luther said.

Already, Marine Studies Associate Prof. S. Craig Cary is using the probe to measure the chemical components of samples retrieved from deep-sea hydrothermal vents. When oceanic plates move in opposite directions, he noted, the resulting volcanic activity can super-heat water deep in the Earth's crust, ejecting it through the ocean floor at temperatures as hot as 680 degrees Fahrenheit. While hydrothermal vents produce dramatic towers of black smoke or "chimneys," he said, they also generate "diffuse-flow sites," where bacterial communities thrive on a diet of hydrogen sulfide. Cary, who has made nine trips to the ocean floor in a submersible vehicle, brings samples of these organisms back to the laboratory, then measures the chemistry of their dynamic habitat, using the microelectrode probe.

# # #

University of Delaware

Related Hydrothermal Vents Articles from Brightsurf:

New ethane-munching microbes discovered at hot vents
Researchers from the Max Planck Institute for Marine Microbiology in Bremen have discovered a microbe that feeds on ethane at deep-sea hot vents.

Hydrogen energy at the root of life
A team of international researchers in Germany, France and Japan is making progress on answering the question of the origin of life.

Solving the mystery of carbon on ocean floor
Little bits of black carbon littering the ocean floor, separate and distinct from the organic carbon believed to come from the ocean's surface.

Deep sea vents had ideal conditions for origin of life
By creating protocells in hot, alkaline seawater, a UCL-led research team has added to evidence that the origin of life could have been in deep-sea hydrothermal vents rather than shallow pools, in a new study published in Nature Ecology & Evolution.

Simple hydrothermal method to produce tin dioxide for lithium-ion battery
In a paper to be published in the forthcoming issue in NANO, a group of researchers led by Wei Zhang from the Yunnan Minzu University, China have developed a simple, low cost and eco-friendly method to synthesize SnO2 nanorods for lithium ion batteries.

Detecting hydrothermal vents in volcanic lakes
Changes in the behaviour of hydrothermal vents may be indicative of changes in the volcanic system underneath, thus being a useful precursor for the next generation of early warning systems.

How deep-ocean vents fuel massive phytoplankton blooms
A new study suggests vents in the seafloor may affect life near the ocean's surface and the global carbon cycle more than previously thought.

Giant X-ray 'chimneys' are exhaust vents for vast energies produced at Milky Way's center
At the center of our galaxy, where an enormous black hole blasts out energy as it chows down on interstellar detritus while neighboring stars burst to life and explode. astronomers have discovered two exhaust channels -- dubbed the 'galactic center chimneys' -- that appear to funnel matter and energy away from the cosmic fireworks.

Japanese student discovers new crustacean species in deep sea hydrothermal vent
A new species of microcrustacean was collected from a submarine hot spring (hydrothermal vent) of a marine volcano (Myojin-sho caldera) in the Pacific Ocean off the coast of Japan.

Microbes from marine volcanic vents reveal how humans adjusted to a changing atmosphere
The findings, published today in Cell by scientists at Van Andel Research Institute (VARI), University of Georgia (UGA) and Washington State University, detail the structure of MBH, a molecular complex involved in microbial respiration.

Read More: Hydrothermal Vents News and Hydrothermal Vents Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to