2003 ASLO Aquatic Sciences Meeting

Sub-theme 4: Extreme Environments On Earth and Beyond

Plenary presentation by Colleen Cavanaugh, Department of Molecular and Cellular Biology, Harvard University

Sub-theme 4 Organizers: Antje Boetius (aboetius@mpi-bremen.de) and Eric Wommack (wommack@dbi.udel.edu)

The organisms that thrive in the conditions present in extreme environments may hold the key(s) to understanding life on early Earth, and elsewhere, as well as evolution of biogeochemical pathways. Sessions related to this sub-theme will examine distribution, physiology and diversity of organisms that thrive under harsh environmental conditions. Topics/habitats to be covered under this sub-theme include, but are not limited to: phylogenetic and functional diversity, extremophiles and extremozymes, symbiosis and syntrophy, deep sea hydrothermal vents and cold seeps, hot springs, polar environments, saline lakes, deep ocean environments, and systems beyond the Earth.

SS4.01 Saline Lakes - Microbial Ecology and Biogeochemistry
Organizer: James T. Hollibaugh (aquadoc@uga.edu)

Saline lakes are often hypersaline and alkaline. Because of the contrast between lake water density and freshwater inflow, they are often meromictic, accumulating high concentrations of toxic reduced substances in bottom waters. The anoxic bottom waters are believed to be reasonable analogues for seas of Noachian Mars or Archaean Earth. This session seeks papers presenting new insights into the microbial ecology and biogeochemistry of saline lake environments.

SS4.03 What is Special About Food Webs in Extreme Environments?
Organizers: Ursula Gaedke (gaedke@rz.uni-potsdam.de), Jorg Tittel, Guntram Weithoff, Elanor Bell

In this session, we seek to attract scientists working on food web theory and investigating the trophic structure of food webs in extreme habitats. The session aims to explore the common properties of food webs in extreme environments, to compare them to those of food webs in less adverse environments and to better understand the mechanisms generating systematic differences. Under extreme abiotic conditions species diversity is typically low and food webs simply structured. Thus, a mechanistic understanding of these food webs may be readily achievable and mathematical models more realistic than for more complex systems. However, individual species may exhibit a wider functional range, e.g. by being mixotrophic or omnivorous. Trophic transfer efficiencies may be altered in food webs of harsh environments, e. g. by high respiratory demands reflecting the higher energetic costs for living under adverse conditions, low quality diets, or spatio-temporal mismatches among few predator and prey species. Differences between food webs in harsh and less adverse habitats can also arise from differences in system age and, hence, time for co-evolution of the component species. Extreme environments may be short-lived or may frequently drive eucaryotes to extinction. We encourage empirical and theoretical contributions emphasizing mechanistic approaches to food web structure and function (e. g. interaction strength, functional insurance) in extreme environments, in order to answer the overall question, which general ecological lessons can be learned from species-poor food webs in extreme habitats.

SS4.04 Symbiosis and Syntrophy in Extreme Environments
Organizers: Nicole Dubilier (ndubilie@mpi-bremen.de) and Douglas C. Nelson (dcnelson@ucdavis.edu)

Without symbioses, life on earth as we know it today would not exist. Symbioses between bacteria and primitive single-celled organisms were crucial for the diversification and evolution of multi-celled, eukaryotic organisms. More recent evolutionary history shows numerous examples of successful syntrophic and symbiotic associations between prokaryotes, and between prokaryotes and eukaryotes. Spectacular forms of such associations have been discovered in extreme environments, for example the syntrophic associations between sulfate-reducing bacteria and methane-oxidizing archaebacteria found at cold seeps that are responsible for anaerobic oxidation of methane. Another example is the symbiotic associations between sulfide- and methane-oxidizing bacteria and marine eukaryotes, that were first discovered at hydrothermal vents, but are now known to occur in other extreme environments such as hypoxic ocean basins, shallow-water vents and pock marks, or sediments around sewage outfalls. The proposed symposium would cover syntrophic and symbiotic interactions between the associated organisms and the interactions of these associations with their extreme environment. Topics of interest for syntrophy would include among others, interspecies hydrogen transfer, phototrophic consortia, and the bacteria-archaebacteria consortia involved in the anaerobic oxidation of methane. Relevant topics for symbiosis would include for example, associations of protists with bacteria and archaebacteria, commonly found in sulfide- and methane-rich ecosystems, bacteria-invertebrate associations from vents, cold seeps and other extreme environments, ecology and biology of free-living thiotrophs and their interaction with the environment, and photosynthetic associations between protists and invertebrates from light-intensive environments.

SS4.05 Microbial Genomics: Resolving the Adaptive Strategies of Bacteria from Extreme Environments
Organizer: Craig Cary (caryc@udel.edu)

Genomic technologies are completely revolutionizing our capability to address complex biological questions and have the potential to dramatically alter how we approach environmental science in the future. A new and developing field is the area of environmental microbial genomics that has begun to harness the genomic technologies catalyzed by the human genome project to help dissect complex microbial systems at the molecular level. These studies have switched the focus of microbial ecology from the phenotypic to the genomic diversity of bacterial populations. Without exception, the results of these studies have confirmed and, indeed, expanded earlier estimates of microbial diversity. Much of the current work in this new area centers on organisms from extreme environments.

SS4.06 Diversity, Ecology, and Biogeochemistry of Microbial Mats and Stromatolites
Organizers: Ferran Garcia-Pichel (ferran@asu.edu), Tori Hoehler (thoehler@mail.arc.nasa.gov), and Brad Bebout (bbebout@mail.arc.nasa.gov)

In the present day, the environmental distribution of well-developed microbial mats is limited largely to extremes of temperature, salinity, or desiccation, where competition and predation are inhibited. However, abundant fossil evidence suggests that microbial mats were widespread on Earth for much of the Precambrian Era, so that these communities must have represented a dominant term in global primary productivity and planetary biogeochemistry. The capacity of microbial mats to act as agents of geochemical change depends critically on the diversity and metabolic potential of the organisms that comprise them, and on the interactions of these organisms with each other and with the environment. This session welcomes contributions on a broad range of topics relating to the ecology and biogeochemistry of microbial mats and stromatolites. Areas of interest include, but are not limited to: phylogenetic and metabolic diversity of mat microorganisms; elemental cycling and trace gas production in microbial mats; interactions among mat microorganisms; factors controlling material fluxes between mats and their environment; and new techniques for microbial mat research.

SS4.07 Microbiology and Biogeochemistry of Cold Seeps
Organizers: Antje Boetius (aboetius@mpi-bremen.de) and Mandy Joye (mjoye@arches.uga.edu)

Cold seeps are abundant along the continental shelf and slope where fluid flow through the sediments is influenced by salt tectonics and other geological processes. At cold seeps, methane and sulfide-laden fluids support prolific chemosynthetic communities consisting of free-living bacteria and archaea, bacteria and archaea living symbiotically, and bacteria living symbiotically with invertebrates. The emission of the greenhouse gas methane from ocean and lakes may have an important impact on the global climate, but rates and budgets of methane turnover in aquatic environments are barely known. This session will focus on the microbiology and biogeochemistry of cold seeps and other methane rich environments aiming to identify common themes and patterns of microbiological distribution and biogeochemical processing that occur in different geologic settings (e.g. accretionary margins, hydrocarbon basins, passive margins, swamps, etc.).

SS4.08 Life in Ice
Organizer: Jody W. Deming (jdeming@u.washington.edu)

Although sea ice and other forms of natural frozen environments have been the subject of biological studies for decades, new motivations and techniques for examining relationships between the ice and its inhabitants have arisen in recent years. Rapidly changing environmental conditions in polar regions portend reductions in the sea-ice cover, such that some forms of life dependent on the ice may face extinction. Activities of communities within ice forms, including sea ice, lake and glacial ice, permafrost and even methane clathrates, are increasingly recognized for their significant contributions to and reflections of large-scale biogeochemical cycles, with connections between land, sea and atmosphere. Evidence for an ice-covered ocean on the Jovian moon Europa, as well as for liquid water associated with the frozen surfaces of Mars, have propelled ice studies into center stage for astrobiology. This session welcomes contributions that address recent advances in the understanding of life in ice, the various strategies evolved to survive at the coldest temperatures on Earth, and the implications for biogeochemical cycles and life elsewhere.

SS4.10 Geomicrobiology of Hydrothermal Vents
Organizers: Katrina J. Edwards (kedwards@whoi.edu) and Stefan M. Sievert (ssievert@whoi.edu)

Hydrothermal vent environments represent biological habitats in which life is juxtaposed between, and dependent on, the physical and chemical conditions created by upper water column biogeochemistry and ocean circulation, heat exchange and magmatic activity in the crust, and fluid-rock interactions at and below the ocean floor. These unique ecosystems are underpinned by chemosynthetic microbiological production that has important evolutionary, ecological, geochemical, mineralogical, and astrobiological ramifications. We invite papers that address these and related geomicrobiological topics concerning hydrothermal vent environments, and anticipate that the session would draw participants from a broad range of backgrounds, both within and potentially outside the range of typical ASLO attendees.

SS4.11 Biochemistry in Extreme Environments
Organizers: Cordelia Arndt (coarndt@uni-greifswald.de) and Horst Felbeck (hfelbeck@ucsd.edu)

The number of organisms, prokaryotes as well as eukaryotes, identified from extreme environments is increasing rapidly. Such environments include those characterized through hot and cold temperatures, extreme pH, high osmolarity, lack of water irregular supply with oxygen, high pressures in the deep sea or deep geological formations, or commonly toxic chemical compositions of the immediate environment. The session should discuss the biochemical adaptations used by organisms to survive or thrive under these conditions, especially adaptations of the metabolic machinery, enzyme functions, and structural components of the cells. What allows life under conditions lethal to most organisms on earth? Which biochemical mechanisms have been changed and how have these adaptations been achieved?


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