"Cave biofilms are simpler than the microbes that occur in soils where there can be hundreds of thousands of species," says Dr. Jennifer L. Macalady, assistant professor of geosciences, Penn State. "Some cave biofilms have very few species, 10 to 20. The more complex ones have 100s or 1,000s."
The researchers investigated the Frasassi cave system located north of Rome and south of Venice in Italy. These limestone caves are like New Mexico's Carlsbad Caverns and Lechuguilla
Cave, but in those caves, sulfur entered the caves from oil and gas reserves, while in Italy, the sulfur source is a thick gypsum layer below. Having sulfur in the environment allows these biofilms to grow.
Most limestone caves form when rainwater and runoff permeate the caves from above. Water and carbon dioxide mix to form carbonic acid, a very weak acid, that erodes the limestone cave walls. In sulfidic caves, water enters the caves from below, carrying hydrogen sulfide. Microbes in the biofilms use the sulfur for energy and produce sulfuric acid, a very strong acid.
"One type of biofilm, called a snottite because of its appearance, has a pH of zero or one," says Daniel S. Jones, graduate student in geosciences. "This is very, very acidic."
Carbonic acid cave systems lose about a third of an inch of wall every thousand years, while sulfuric acid cave systems lose about two and a third inches or six times as much in the same time. The researchers are interested in the make-up of the biofilms and how they cycle sulfur.
Biofilms are made up of thin layers of microbe species that can be very different. All require water, but some biofilms live in the pools, lakes and streams in caves and others live on the damp walls. The layers against the rock surface use oxygen and hydrogen sulfide for energy and produce sulfuric acid. The layer on the outside does as well, but, because middle layers exist, there is an opportunity for microbes that find oxygen poisonous to thrive. These middle layers may convert the sulfuric acid to hydrogen sulfide, creating a complete sulfur cycle in a few microns.
In dental biofilms, the microbes on the teeth are the ones that produce the acids that cause cavities, while the ones on the top create the right conditions for the acid-producing microbes to survive. Cave biofilm layers also fulfill different niches in their very tiny environment.
"Stream biofilms are responsible for the majority of sulfide disappearance in streams," Jones told attendees today (Dec. 11) at the fall meeting of the American Geophysical Meeting in San Francisco.
Because the cave biofilms are relatively simple, it will be easier to connect the various microbe species to the geochemistry involved. While this work is not yet complete, the researchers are working on the problem. Dr. Greg K. Druschel, assistant professor of geology, University of Vermont, used microelectrode voltammetry to try to determine exactly which biofilm layers produce acids. The levels of hydrogen sulfide and sulfuric acid change, depending on which layer is tested.
"There is also a question about where these microbes originate," says Macalady. "We do not know if they are always in rocks or if they are transported from somewhere else to establish themselves."
No matter the answer, the biofilms probably begin growing in tiny cracks in the rock and eventually create some of the largest cave systems in the world. Cave biofilms are also the bottom of the food chain for cave ecosystems. They provide food for a variety of spiders, flat worms, pill bugs and amphipods – shrimp like crustaceans – that form a blind and pigmentless community.
"The only other place we find sulfur-based ecosystems is near the deep sea vents on the ocean floor," says Jones.
Understanding how cave biofilms dissolve calcium carbonate may help us to understand the communities around ocean floor vents, but it may also, eventually, lead to understanding how biofilms dissolve calcium phosphate on teeth and the steel hulls of ships.
UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine
Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union
Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.
So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
28.10.2016 | Power and Electrical Engineering
28.10.2016 | Physics and Astronomy
28.10.2016 | Life Sciences