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PreprintInsights into foraminiferal influences on microfabrics of microbialites at Highborne Cay, Bahamas( 2013-03-15) Bernhard, Joan M. ; Edgcomb, Virginia P. ; Visscher, Pieter T. ; McIntyre-Wressnig, Anna ; Summons, Roger E. ; Bouxsein, Mary L. ; Louis, Leeann ; Jeglinski, MarleenMicrobialites, 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.
ArticleTechnical Note : Towards resolving in situ, centimeter-scale location and timing of biomineralization in calcareous meiobenthos – the calcein–osmotic pump method(Copernicus Publications on behalf of the European Geosciences Union, 2015-09-28) Bernhard, Joan M. ; Phalen, William G. ; McIntyre-Wressnig, Anna ; Mezzo, Francesco ; Wit, Johannes C. ; Jeglinski, Marleen ; Filipsson, Helena L.Insights into oceanographic environmental conditions such as paleoproductivity, deep-water temperatures, salinity, ice volumes, and nutrient cycling have all been obtained from geochemical analyses of biomineralized carbonate of marine organisms. However, we cannot fully understand geochemical proxy incorporation and the fidelity of such in species until we better understand fundamental aspects of their ecology such as where and when these (micro)organisms calcify. Here, we present an innovative method using osmotic pumps and the fluorescent marker calcein to help identify where and when calcareous meiofauna calcify in situ. Method development initially involved juvenile quahogs (Mercenaria mercenaria); subsequent method refinement involved a neritic benthic foraminiferal community. Future applications of this method will allow determining the in situ growth rate in calcareous organisms and provide insights about microhabitats where paleoceanographically relevant benthic foraminifera actually calcify.