Collaborative Research: Microbial Observatory at an Alkaline, Hypersaline, Meromictic Lake (Mono Lake, California)

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The Microbial Observatory focuses on the microbes found in Mono Lake, an alkaline, hypersaline, currently meromictic (lighter, less saline water overlies heavier, more saline water throughout the year) lake located east of the Sierra Nevada in California. There are a number of reasons why Mono Lake is an ideal site for a Microbial Observatory. It is a well-defined, ecologically simple, microbially dominated ecosystem for which long-term ecological and limnological data exist. Mono Lake is a hydrologically simple system, which makes modeling tractable, yet it contains complex gradients of chemical and physical variables as a result of meromixis. The lake is located close to a major field station (the Sierra Nevada Aquatic Research Laboratory, administered by the University of California, Santa Barbara). There are ongoing studies of the lake's physics, plankton ecology and biogeochemistry that provide a comprehensive framework for the microbial studies. Mono Lake is currently undergoing a human-induced (and thus predictable) limnological transition which imparts a predictable temporal trajectory to physical, biogeochemical and ecological processes. This change mirrors past, natural events in Great Basin lakes resulting from climate oscillations and similar, if less extreme, changes in physical limnology might be expected in other lakes. Mono Lake represents an extreme environment that is likely to harbor unique microbes. However, relatively little is known about the types of microorganisms dwelling in Mono Lake, their phylogenetic diversity, taxonomy, ecology or ecophysiology. For example, recent phylogenetic analysis of an important phytoplankton demonstrates it to be a new class of algae with unusual physiological properties and biochemical composition. While abundant bacterial populations and the existence of pronounced bacterial plates have been noted before in Mono Lake, the temporal and spatial variation in diversity of the bacterial community has only recently begun to be investigated. The primary goal of this research is to examine the distributions of Mono Lake microbes and to understand the response of microbial assemblages to the gradients of physical and chemical variables in relation to temporal changes driven by hydrodynamics. The specific objectives of the project are to: 1) Identify and characterize the microbial assemblages in the unique Mono Lake ecosystem. 2) Determine the spatial and temporal variation of the Mono Lake microbial assemblage, particularly in reference to evolving meromixis. 3) Determine the response of the microbial community to physical processes, especially short-term and small-scale variation in mixing (for example, enhanced vertical diffusion as a result of boundary mixing or localized gravitational circulation). 4) Provide a mechanistic understanding of the interactions between the physical/chemical structure and microbial assemblages as the basis for predictive (long-term) modeling of the relationship between microbial processes, lake biogeochemistryand primary production. This project provides a unique opportunity to identify novel microorganisms and define interactions among microorganisms in complex gradients of physical/chemical conditions usually only encountered at sediment-water interfaces. This is a collaborative project involving Drs. James Hollibaugh and Samantha Joye, University of Georgia, award #9977886, Dr. Robert Jellison, University of California, Santa Barbara (#9977901) and Dr. Jonathan Zehr, University of California, Santa Cruz (#9977892).