Insights into foraminiferal influences on microfabrics of microbialites at Highborne Cay, Bahamas

Abstract

Microbialites, which are organosedimentary structures formed by microbial communities through binding and trapping and/or in situ precipitation, have a wide array of distinctive morphologies and long geologic record. The origin of morphological variability is hotly debated; elucidating the cause or causes of microfabric differences could provide insights into ecosystem functioning and biogeochemistry during much of Earth's history. Although rare today, morphologically distinct, co-occurring extant microbialites provide the opportunity to examine and compare microbial communities that may be responsible for establishing and modifying microbialite microfabrics. Highborne Cay, Bahamas, has extant laminated (i.e., stromatolites) and clotted (i.e., thrombolites) marine microbialites in close proximity, allowing focused questions about how community composition relates to physical attributes. Considerable knowledge exists about prokaryotic composition of microbialite mats (i.e., stromatolitic and thrombolitic mats), but little is known about their eukaryotic communities, especially regarding heterotrophic taxa. Thus, the heterotrophic eukaryotic communities of Highborne stromatolites and thrombolites were studied. Here, we show that diverse foraminiferal communities inhabit microbialite mat surfaces and subsurfaces; thecate foraminifera are relatively abundant in all microbialite types, especially thrombolitic mats; foraminifera stabilize grains in mats; and thecate reticulopod activities can impact stromatolitic mat lamination. Accordingly, and in light of foraminiferal impacts on modern microbialites, our results indicate that the microbialite fossil record may reflect the impact of the radiation of these protists.Neoproterozoic | geobiology | sedimentology | ooid

External controls on the distribution, fabrics and mineralization of modern microbial mats in a coastal hypersaline lagoon, Cayo Coco (Cuba)

“…hypersaline conditions, extreme irradiance, low/high temperature, acidic/alkaline pH and high amounts of sulphur/iron; Des Marais, ; Visscher et al ., ), in which most predators and/or competitors are absent (Garrett, ). Some protists and metazoans use microbial biofilms as a food source (Farmer, ; Bernhard et al ., ), thereby preventing the preservation of microbial mats. The decline of microbialites during the late Precambrian has been explained by the radiation of metazoans (Garrett, ; Awramik, ; Grotzinger, ), but some recent works question this common assumption (Brayard et al ., ; Tarhan et al ., ; Edgcomb et al ., ).…”

Unravelling core microbial metabolisms in the hypersaline microbial mats of Shark Bay using high-throughput metagenomics

“…The dominance of marine stromatolites collapsed~542 Myr ago, possibly due to eukaryotic grazing (Bernhard et al, 2013). These communities thrive at the intersection of abiotic and biotic factors that promote organomineralisation (Dupraz and Visscher, 2005;Dupraz et al, 2009).…”

Gene Sequencing-Based Analysis of Microbial-Mat Morphotypes, Caicos Platform, British West Indies

“…Although it is unclear what processes determine the morphology of microbial mats, hypotheses include: microbial community composition (Gerdes et al 2000;Golubic et al 2000;Dupraz and Visscher 2005;Noffke 2010;Shepard and Sumner 2010), metazoan and protistan grazing (Garrett 1970;Bernhard et al 2013), hydrodynamics and sedimentation (Gebelein 1969;Martin et al 1993;Andres and Reid 2006;Mariotti et al 2014), and other environmental factors (Wharton et al 1983;Gerdes et al 2000;Petroff et al 2010). In modern environments, microbial mats in tidal flats, sabkhas, and shallow subtidal zones are commonly considered analogs and possible precursors to stromatolites (e.g., Browne et al 2000;Dupraz et al 2009).…”