Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic
"The million-year variability of the marine nitrogen cycle is poorly understood. Before 57 million years (Ma) ago, the 15N/14N ratio (δ15N) of foraminifera shell-bound organic matter from three sediment cores was high, indicating expanded water column suboxia and denitrification. [...]"
Authors: Emma R. Kast et al.
Metabolic preference of nitrate over oxygen as an electron acceptor in foraminifera from the Peruvian oxygen minimum zone
"Benthic foraminifera populate a diverse range of marine habitats. Their ability to use alternative electron acceptors—nitrate (NO3−) or oxygen (O2)—makes them important mediators of benthic nitrogen cycling. Nevertheless, the metabolic scaling of the two alternative respiration pathways and the environmental determinants of foraminiferal denitrification rates are yet unknown. We measured denitrification and O2 respiration rates for 10 benthic foraminifer species sampled in the Peruvian oxygen minimum zone (OMZ). [...]"
Authors: Nicolaas Glock et al.
Mid-Holocene deepening of the Southeast Pacific oxycline
"This study presents new high resolution sedimentary δ15N records from piston cores collected within and outside the present-day eastern south Pacific oxygen minimum zone along a latitudinal transect from 3.5°S to 15°S. Radiocarbon dating of foraminifera and organic matter show that the cores cover the Holocene and the last deglaciation with high sedimentation rate allowing interpretations at millennial to centennial timescale. [...]"
Source: Global and Planetary Change
Authors: Elfi Mollier-Vogel et al.
Deep-Water Dynamics in the Subpolar North Atlantic at the End of the Quaternary
"In the subpolar North Atlantic, four sediment cores were taken. All of them were suitable for reconstructing the dynamics of the meridional overturning circulation in the late Quaternary. Stratigraphy of the cores was performed by carbonate analyses, study of planktonic foraminifera, and oxygen isotopic composition in Neogloboquadrina pachyderma sin. Study of benthonic foraminifera assemblages has shown significant differences in the deep-water dynamics in the late Quaternary related to water exchange between the North Atlantic and Arctic seas. [...]"
Authors: N.P. Lukashina
Last interglacial ocean changes in the Bahamas: climate teleconnections between low and high latitudes
"Paleorecords and modeling studies suggest that instabilities in the Atlantic Meridional Overturning Circulation (AMOC) strongly affect the low-latitude climate, namely via feedbacks on the Atlantic Intertropical Convergence Zone (ITCZ). Despite the pronounced millennial-scale overturning and climatic variability documented in the subpolar North Atlantic during the last interglacial period (MIS 5e), studies on cross-latitudinal teleconnections remain very limited. This precludes a full understanding of the mechanisms controlling subtropical climate evolution across the last warm cycle. [...]"
Source: Climate of the Past
Authors: Anastasia Zhuravleva and Henning A. Bauch
A Novel Eukaryotic Denitrification Pathway in Foraminifera
"Benthic foraminifera are unicellular eukaryotes inhabiting sediments of aquatic environments. Several species were shown to store and use nitrate for complete denitrification, a unique energy metabolism among eukaryotes. The population of benthic foraminifera reaches high densities in oxygen-depleted marine habitats, where they play a key role in the marine nitrogen cycle. However, the mechanisms of denitrification in foraminifera are still unknown, and the possibility of a contribution of associated bacteria is debated. Here, we present evidence for a novel eukaryotic denitrification pathway that is encoded in foraminiferal genomes. [...]"
Source: Current Biology
Authors: Christian Woehle et al.
How nutrients are removed in oxygen-depleted regions of the ocean
"In the course of global climate change, scientists are observing the increase of low-oxygen areas in the ocean, also termed oxygen minimum zones (OMZs). Large-scale OMZs exist, for example, in the Pacific off the coast of South America or in the Indian Ocean. Since little to no oxygen is present in these regions - depending on the depth of the water - organisms whose metabolisms is independent of oxygen have a distinct advantage. These organisms include some representatives of the foraminifera: unicellular, shell-forming microorganisms, which have a nucleus and thus belong to the eukaryotes. Their life style involves a particular metabolic pathway termed anaerobic respiration. In the absence of oxygen, they convert nitrate present in the water into molecular nitrogen. [...]"
Source: Kiel University
New insights into Cenomanian paleoceanography and climate evolution from the Tarfaya Basin, southern Morocco
"A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carboncontent, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. [...]"
Source: Cretaceous Research
Authors: Sebastian Beil et al.
Mn∕Ca intra- and inter-test variability in the benthic foraminifer Ammonia tepida
"The adaptation of some benthic foraminiferal species to low-oxygen conditions provides the prospect of using the chemical composition of their tests as proxies for bottom water oxygenation. Manganese may be particularly suitable as such a geochemical proxy because this redox element is soluble in reduced form (Mn2+) and hence can be incorporated into benthic foraminiferal tests under low-oxygen conditions. [...]"
Authors: Jassin Petersen et al.
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Ecophenotypic responses of benthic foraminifera to oxygen availability along an oxygen gradient in the California Borderland
"Spatial variation in environmental conditions can elicit predictable size and morphological responses in marine organisms through influences on physiology. Thus, spatial and temporal variation in marine organism size and shape are often used to infer paleoenvironmental conditions, such as dissolved oxygen concentrations. Benthic foraminifera commonly serve as a tool for reconstructing past ocean oxygen levels. [...]"
Source: marine ecology
Authors: Caitlin R. Keating-Bitonti, Jonathan L. Payne