Collaborative Research: Alteration of microbially-produced carbonate rock by unicellular predators to better understand early Earth's dominant ecosystem

University Of Connecticut, Storrs CT

Investigators

Abstract

Collaborative Research: Alteration of microbially-produced carbonate rock by unicellular predators to better understand early Earth's dominant ecosystem How Earth transitioned from a microbe-dominated Precambrian world to the Phanerozoic Era with complex multicellular life is a continuing geological and biological riddle. Studying living microbialites (carbonate rocks built by microbes, ancient counterparts of coral reefs) in Fayetteville Green Lake, NY, will help solve this riddle. This interdisciplinary study will reveal how the internal structure of these living rocks is formed by microbes and how it is altered by the action of microscopic unicellular predators (so-called protists). Understanding the role of protists in living examples will help to decipher microbialites in the rock record, ultimately improving understanding of the evolution of life on early Earth. The petroleum industry seeks to improve understanding of microbialites' microstructure. The discovery of large subsalt reservoirs off the coast of Brazil, Congo, Eritrea and in the US Gulf of Mexico challenged oil companies to understand the record of very deep (~1-2 km thick) fossil microbialites present underneath an equally thick salt layer. This project will increase the understanding of fabric porosity, and reservoir rocks, critical factors in decision-making during oil exploration. The major outreach activity will be a Science through Art traveling exhibition related to microbialite ecosystems and predation on early Earth, with a tentative title of "Decimation of Slime World" (in other words, predation of microbialites). This theme will generate wide interest, and will offer explanations about the research findings in ways that would otherwise escape the art-loving public sector. The oldest fossil microbialites are the most visible manifestations of microbial life on early Earth. Comprehension of structural differences between microbialite types (e.g., clotted thrombolites, laminated stromatolites) is hampered by incomplete knowledge of their microbiology and early diagenesis. Prokaryotic diversity in extant marine microbialites is well established, however, until recently heterotrophic protists inhabiting these structures and their impact on mesofabric were unknown. A comparative study of non-marine microbialites is lacking. Fayetteville Green Lake NY (FGL), a Proterozoic ocean analog, supports extant microbialites in a non-marine setting. Investigations will assess the role of eukaryotes, notably protists, in microbialite fabric modification and in the possible transition from laminated to clotted mesofabrics during early diagenesis. Four hypotheses will be addressed using FGL materials with these specific aims: 1. Assess biodiversity and activities in microbialites and non-microbialite habitats via sequencing, Fluorescently Labeled Embedded Core method, and various microscopy methods. 2. Determine biogeochemistry using microelectrodes and major in situ microbial activities to link microbiota, element distribution, and mesofabric. 3. Obtain microbialite mesofabric information using microCT scanning. 4. Combine SEM-EDS and Synchrotron-based microXRF to analyze mesofabric features, especially clots, for presence of pyrite and biogenic metals. 5. Determine impact of foraminifera on microbialite mesofabric using seeding experiment. 6. Perform ?forced diagenesis? by incubating microbialite samples under elevated pressure/temperature, inspecting changes in mesofabric using SEM, µCT and µXRF scanning. 7. Use SEM and petrographic thin sections to examine relict thrombolite mesofabric for former eukaryote activity/presence.