nai

Project Progress

Cuatro Ciénegas is a unique biological preserve in México (state of Coahuila) in which there is striking microbial diversity, potentially related to extreme scarcity of phosphorus. We aim to understand this relationship via field sampling of biological and chemical characteristics and a series of enclosure and whole-pond fertilization experiments.

Accomplishments

Overview of CC: During 2011 members of our completed and published several manuscripts reviewing the microbiological and astrobiological attributes of the Cuatro Ciénegas basin. Our work also caught the attention of Nature magazine, which produced a News article (“Gene pool offers way to save Mexican oasis”) related to Valeria Souza’s effort to advance conservation of the Cuatro Ciénegas basin by deploying the Nagoya Protocol to return potential benefits from genetic resources of the valley to its citizens.

Phosphorus limitation and element use in microbial communities: During a week-long field trip in February 2011 we were successful in designing, supervising construction of, and installing a large welded-steel frame at the small pond in the Churince drainage, “La Lagunita”. This platform was then used in performing a six-week mesocosm nutrient (N, P) fertilization experiment during May / June 2011. Four treatments were applied (n=5 replicates): control; +P, +NP (16:1), and +NP (75:1). Controls received no nutrients; +P received PO₄-P sufficient to return ambient concentration to 1.0 uM at ~3- to 7-day intervals); +NP(16) was similar to +P except N was also added (as NH₄NO₃) in a 16:1 ratio with P; and +NP(75) was similar to +NP(16) except N was added at a 75:1 ratio. The enrichments continued for three weeks at which time major sampling occurred. After this, enrichments were stopped in order to evaluate possible recovery responses. Mesocosms were sampled for basic variables at weekly intervals and for major variables, including biomass stoichiometry and microbial community composition, after 3 weeks and at the end of the experiment. Samples are now being processed to assess changes in elemental composition (“extended Redfield ratio”) as well as shifts in microbial community structure and physiological state using meta-genomic and meta-transcriptomics.

Environmental microbiology. UNAM researcher Valeria Souza continued to advance studies in association with the NASA NAI project to describe the genetic composition and microbial community structure of various ecosystems at Cuatro Ciénegas, including soil and sediment microbes as well as the microbes composing various stromatolite structures in the basin. Various publications and manuscripts have resulted and are listed elsewhere in this report.

Calcification, nutrient cycling, and microbial community structure in Río Mezquites stromatolites
PhD student Jessica Corman continued her work to understand formation of, and nutrient cycling processes associated with, oncoid stromatolites. During summer 2011, she deployed artificial substrates in Río Mesquites to determine abiotic and biotic processes of oncoid development. She also performed an experimental manipulation of the effects of calcification rates on microbial community development. Working with postdoc Amisha Poret-Peterson and Corman, undergraduates Eric Hughes and Alisa Glukhova have optimized extraction methods of DNA and RNA from biogenic carbonate microbial communities. Alisa is using these methods to characterize the response of oncoid microbial communities to changes in nutrient and light availability with T-RFLP analysis. Postdocs Zarraz Lee (ASU) and Christine Rooks (UNAM) also are also optimizing methods for FISH (Fluorescence In Situ Hybridization) analysis.

Environmental, microbial, and stoichiometric diversity at Cuatro Ciénegas
In continuation of regular environmental sampling, PhD students Jessica Corman and Jorge Ramos sampled over 30 distinct water bodies in the valley during summer and fall 2011. Water and sediment samples were collected for major and minor elemental analysis. Jessica Corman also continued the ecological and microbiological monitoring of succession in the Pozas Rojas, an area of (formerly) saline pools that was affected by a massive flood in July 2010. The area is now drying and the pools are re-forming with increasing levels of salinity.