Volcano Fields
Introduction
Volcano fields are unique ecosystems found around the world’s active volcanoes. A volcano field usually encompasses any number of active volcanoes clustered together in relatively close quarters. These environments are characterized by magma and ash as soil parent material and often exhibit early stages of succession in an ecosystem. Frequent disturbance of volcanic activity can prevent succession from proceeding to high orders. These eruptions can produce or displace magma, rock, or ash, depending on unique characteristics of every volcano or eruption event.
These areas are quite special because they represent the spearhead of geologic time. Materials from the earth’s inner layers are introduced to the lithosphere and atmosphere, which can cause interesting phenomena among microbial populations.
The microbial populations found in such areas are categorized by their abilities to process the new or changed materials on the earth’s surface. Although disturbance is high right near the source of magma and ash flows, these flows do not always cover an area completely, which provides physical, chemical, and biological diversity between and across sites near a volcano.
Microorganisms that occupy these areas are typically extremophiles that tolerate high heat, and are often oxidize CO and utilize methanogenesis. These early processes help prepare the lava and ash deposits to be suitable to support higher life forms.
Physical environment
The physical environment of a volcano field is somewhat diverse, as the materials present can come from lava flows or ash flows. Also, they change dramatically over time due to microbial and atmospheric weathering processes.
Very high concentrations of silicates cause lava to be an acidic environment, suitable for acidophiles, while less acidic flows are represented by a lower concentration of silicate material.
Microorganisms colonize recent volcanic deposits and are able to establish diverse communities, their composition is governed by variations in local deposit parameters.
Along with solid and liquid rock material ejected by volcanoes, many gases are ejected and are often trapped in the solids on the ground once the lava cools. These gases can be used by microbes for gas exchange and metabolic processes. Methane, for example, is common in erupted material, and is used by methanotrophic bacteria for energy and carbon uptake.
Lava Flows
A brand new lava flow is likely to have a high concentration of silicate, with significant amounts of aluminum, potassium, sodium, and calcium found throughout. Differences in silicate concentrations affect the viscosity of the medium, changing the manner of eruption, flow, and after-effects.
Mafic Lava
Mafic, or basaltic, lava is high in iron and magnesium and lower in aluminum and silicates. This lava is not very viscous, so it often cools with smooth yet rippled surface patterns, as opposed to blocky and jagged Felsic deposits.
Felsic Lava
Felsic lava is very viscous, and has a higher concentration of silicate material, and produces a very blocky pattern as it cools.
Ash Flows
An ash flow is a typical eruption of highly gaseous magma. The large amount of gas causees eruptions to be explosive, launching ash and debris very high into the air. The ash and debris will fall to the ground near the volcano (sometimes a few miles away) and supply the microbes with a fresh source of minerals to metabolize for energy.
Gases emitted during these eruptions are mostly H2O, CO2, SO2, H2, CO, H2S, and HCl. These gases are released into the atmosphere most often, but are also found within pieces of ejected or erupted material.
Physical Succession
Succession from bare lava flow to forest occurs over time, as living things, from microbes to animals, change the landscape by living in and around it. Microbes are always present first because certain types are able to withstand the extreme heat involved with lava flows.
Chemolithoautotrophs use the materials in recent lava flows for energy first(the earliest users being thermophiles). Breakdowns cause soils to start to form, allowing plant life to establish. Plant life will draw in animal grazers, which both help the soil develop further by physically altering its structure.
Biological interactions
Important biological interactions in volcano fields are quite like many other ecosystem; the microbes and fungi allow plants to utilize nutrients that would be otherwise inaccessible. A major difference in succession and early interactions in a volcano field could come from the extremely high intensity of disturbances. Lava and ash eruptions can cause catastrophic damage to an ecosystem, often forcing succession to restart.
Once microbes change the soils, a process involved in Pedogenosis to support plant life, plants will be able to grow and reproduce, which allows the primary succession plants to immigrate to the newly formed soils. When plants establish, their roots can break up the volcanic deposits, allowing more gas-exchange and atmospheric interactions to shape the composition and structure of the soils. When more air is present in the volcanic soils, more microbial activity can take place due to the increased gas exchange capabilities.
When plant life has established itself in an area, there will often be animal life to use the plants for food and shelter. Herbivores will spread the microbes and plant seeds, allowing travel of such organisms to increase, which can increase the beta diversity of the field. Over time, volcanic fields proceed to higher levels of succession if the interval between eruptions is long enough for such to occur.
Microbial processes
According to the Kilauea Volcano Microbial Observatory (1), Carbon monoxide oxidation and methanotrophy are two major processes that shape the chemical makeup of a volcano field.
Due to the high levels of sulfur gases found in volcanic chemical makeup, sulfur metabolism is utilized by microbes of the Thiobacillus, Thiosphaera, and other sulfur metabolizing bacteria.
CO Oxidation
Consumption of CO by bacteria allows for a balance between abiotic creation of CO and metabolizing CO.
Methanotrophy
Methanotrophs are able to use methane as their primary source of carbon and energy.
Sulfur Metabolism
Bacteria that metabolize sulfur are important to volcano fields, as sulfur is often brought to the lithosphere during eruption events.
Key Microorganisms
Extremophiles, specifically thermophiles, are found in and around areas home to recent eruptions. CO oxidizers and Methanotrophs are two important types of bacteria found after the lava or ash has cooled. These organisms utilize endospores to face the extreme heat involved with volcanoes.
Thermophiles
Microbes that flourish in extreme heat are known as thermophiles. They can also be found in Yellowstone Hot Springs and Hydrothermal Vents on the ocean floor.
These organisms are often acidophilic, which gives them the ability to occupy the extremely hot and acidic environment involved near active volcanoes.
CO Oxidizers
CO Oxidizers will oxidize carbon monoxide in order to obtain electrons for energy. These bacteria help maintain the balance of CO in volcanic soils by acting as a counterpart to abiotic production of CO.
Methanotrophs
Methanotrophs metabolize methane as their only source of carbon and energy.
Sulfur Immobilizers
Beggiatoa are one genus of proteobacteria that metabolize sulfur for energy. These organisms play an important role in the sulfur cycle.
Examples of organisms within the group
Pseudomonas
Burkholderia
Mycobacterium
Current Research
http://www.biology.lsu.edu/kmo/forms/King-Crosby.pdf
CO production and use is examined in legumes and non-legumes, comparing the production and consumption of CO by plant roots. A balance is achieved by the microbial use and abiotic production of CO. The balance is achieved due to the microbial responses to changing CO availability.
http://www.biology.lsu.edu/kmo/forms/GMKanoxicCOox.pdf
Nitrate reducing and denitrifying isolates were compared in their ability and efficiency in their contributions to the Nitrogen Cycle and CO consumption under anaerobic conditions in the presence of nitrate. It was found that aerobic conditions allowed for increased CO consumption and acetogenic bacteria may play a role in CO uptake.
http://www.biology.lsu.edu/kmo/forms/Nanbaetal04.pdf
PCR products of sulfur-oxidizing microbial mats were analyzed to produce clone libraries of volcanic microbial communities. These libraries were found to be dominated by facultative lithotrophs. Proportions of microbial sulfur oxidation was correlated with respiration estimations.
References
(1) Kilauea Volcano Microbial Observatory
(2) Volcanic Gases and Their Effects
(3) Distribution, diversity and ecology of aerobic CO-oxidizing bacteria
University of Illinois class NRES 475: Environmental Microbiology class notes
(5) Nitrate-dependent anaerobic carbon monoxide oxidation by aerobic CO-oxidizing bacteria
Edited by Randall D. McConnell, student of Angela Kent at the University of Illinois at Urbana-Champaign.
