PAIRED ANALYSES OF FINE-SCALE SEDIMENT GEOCHEMISTRY AND LIVE BENTHIC FORAMINIFERAL DISTRIBUTIONS IN MUDFLAT CHEMOCLINES (Invited Presentation)

Our ability to properly interpret microfossils hinges on accurate and precise understanding of the environments that existed during growth of the microscopic organisms that generated the potential fossil(s). Using the premise that the key to interpreting the past is to comprehend the present, we focus on better defining the biogeochemical capabilities of extant benthic foraminifera. Thus, in an effort to further understand extant benthic foraminiferal distributions in sedimentary environments with steep geochemical gradients, we are refining select geochemical and ecological methods for compatible paired analyses. The Fluorescently Labeled Embedded Core (FLEC) method preserves enzymatically active foraminifera in their life position at the sub-millimeter scale, in three dimensions. Geochemical methods combining two-dimensional diffusive equilibrium thin gel films (thin-film DET) and spectrophotometry have recently been developed to map dissolved pore-water constituents at similar fine scales (sub-millimeter). This contribution will present our progress toward refining these methods to enable paired analyses of, for example, nitrite, nitrate, ammonium, dissolved reactive phosphorous, dissolved iron and/or hydrogen sulfide with foraminiferal distributions in samples from the chemocline of tidal mudflats from the Baie of Bourgneuf, France. Efforts are underway to include solid-phase assessments such as hyperspectral analyses and micro-XRF (x-ray fluorescence) in our suite of analyses. Funded by FRESCO, RS2E-OSUNA, COSELMAR (Pays de la Loire Region), The Investment in Science Fund at WHOI, and the Robert W. Morse Chair for Excellence in Oceanography at WHOI.