Bernhard Joan M.

No Thumbnail Available
Last Name
First Name
Joan M.

Search Results

Now showing 1 - 20 of 58
  • Preprint
    Identity of epibiotic bacteria on symbiontid euglenozoans in O2-depleted marine sediments : evidence for symbiont and host co-evolution
    ( 2010-06) Edgcomb, Virginia P. ; Breglia, S. A. ; Yubuki, Naoji ; Beaudoin, David J. ; Patterson, David J. ; Leander, Brian S. ; Bernhard, Joan M.
    A distinct subgroup of euglenozoans, referred to as the “Symbiontida,” has been described from oxygen-depleted and sulfidic marine environments. By definition, all members of this group carry epibionts that are intimately associated with underlying mitochondrion-derived organelles beneath the surface of the hosts. We have used molecular phylogenetic and ultrastructural evidence to identify the rod-shaped epibionts of two members of this group, Calkinsia aureus and Bihospites bacati, hand-picked from sediments from two separate oxygen-depleted, sulfidic environments. We identify their epibionts as closely related sulfur or sulfide oxidizing members of the Epsilon proteobacteria. The Epsilon proteobacteria generally play a significant role in deep-sea habitats as primary colonizers, primary producers, and/or in symbiotic associations. The epibionts likely fulfill a role in detoxifying the immediate surrounding environment for these two different hosts. The nearly identical rod-shaped epibionts on these two symbiontid hosts provides evidence for a co-evolutionary history between these two sets of partners. This hypothesis is supported by congruent tree topologies inferred from 18S and 16S rDNA from the hosts and bacterial epibionts, respectively. The eukaryotic hosts likely serve as a motile substrate that delivers the epibionts to the ideal locations with respect to the oxic/anoxic interface whereby their growth rates can be maximized, perhaps also allowing the host to cultivate a food source. Because symbiontid isolates and additional SSU rDNA gene sequences from this clade have now been recovered from many locations worldwide, the Symbiontida are likely more widespread and diverse than presently known.
  • Preprint
    Denitrification likely catalyzed by endobionts in an allogromiid foraminifer
    ( 2011-10) Bernhard, Joan M. ; Edgcomb, Virginia P. ; Casciotti, Karen L. ; McIlvin, Matthew R. ; Beaudoin, David J.
    Nitrogen can be a limiting macronutrient for carbon uptake by the marine biosphere. The process of denitrification (conversion of nitrate to gaseous compounds, including N2) removes bioavailable nitrogen, particularly in marine sediments, making it a key factor in the marine nitrogen budget. Benthic foraminifera reportedly perform complete denitrification, a process previously considered nearly exclusively performed by bacteria and archaea. If the ability to denitrify is widespread among these diverse and abundant protists, a paradigm shift is required for biogeochemistry and marine microbial ecology. However, to date, the mechanisms of foraminiferal denitrification are unclear and it is possible that the ability to perform complete denitrification is due to symbiont metabolism in some foraminiferal species. Using sequence analysis and GeneFISH, we show that for a symbiont-bearing foraminifer, the potential for denitrification resides in the endobionts. Results also identify the endobionts as denitrifying pseudomonads and show that the allogromiid accumulates nitrate intracellularly, presumably for use in denitrification. Endobionts have been observed within many foraminiferal species, and in the case of associations with denitrifying bacteria, may provide fitness for survival in anoxic conditions. These associations may have been a driving force for early foraminiferal diversification, which is thought to have occurred in the Neoproterozoic when anoxia was widespread.
  • Article
    Ultrastructure and molecular phylogeny of Calkinsia aureus : cellular identity of a novel clade of deep-sea euglenozoans with epibiotic bacteria
    (BioMed Central, 2009-01-27) Yubuki, Naoji ; Edgcomb, Virginia P. ; Bernhard, Joan M. ; Leander, Brian S.
    The Euglenozoa is a large group of eukaryotic flagellates with diverse modes of nutrition. The group consists of three main subclades – euglenids, kinetoplastids and diplonemids – that have been confirmed with both molecular phylogenetic analyses and a combination of shared ultrastructural characteristics. Several poorly understood lineages of putative euglenozoans live in anoxic environments, such as Calkinsia aureus, and have yet to be characterized at the molecular and ultrastructural levels. Improved understanding of these lineages is expected to shed considerable light onto the ultrastructure of prokaryote-eukaryote symbioses and the associated cellular innovations found within the Euglenozoa and beyond. We collected Calkinsia aureus from core samples taken from the low-oxygen seafloor of the Santa Barbara Basin (580 – 592 m depth), California. These biflagellates were distinctively orange in color and covered with a dense array of elongated epibiotic bacteria. Serial TEM sections through individually prepared cells demonstrated that C. aureus shares derived ultrastructural features with other members of the Euglenozoa (e.g. the same paraxonemal rods, microtubular root system and extrusomes). However, C. aureus also possessed several novel ultrastructural systems, such as modified mitochondria (i.e. hydrogenosome-like), an "extrusomal pocket", a highly organized extracellular matrix beneath epibiotic bacteria and a complex flagellar transition zone. Molecular phylogenies inferred from SSU rDNA sequences demonstrated that C. aureus grouped strongly within the Euglenozoa and with several environmental sequences taken from low-oxygen sediments in various locations around the world. Calkinsia aureus possesses all of the synapomorphies for the Euglenozoa, but lacks traits that are specific to any of the three previously recognized euglenozoan subgroups. Molecular phylogenetic analyses of C. aureus demonstrate that this lineage is a member of a novel euglenozoan subclade consisting of uncharacterized cells living in low-oxygen environments. Our ultrastructural description of C. aureus establishes the cellular identity of a fourth group of euglenozoans, referred to as the "Symbiontida".
  • Preprint
    Impact of intentionally injected carbon dioxide hydrate on deep-sea benthic foraminiferal survival
    ( 2008-10) Bernhard, Joan M. ; Barry, James P. ; Buck, Kurt R. ; Starczak, Victoria R.
    Sequestration of carbon dioxide (CO2) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean acidification may affect marine fauna. In an effort to understand better the protistan reaction to such an environmental perturbation, the survivorship of benthic foraminifera, which is a prevalent group of protists, was studied in response to deep-sea CO2 release. The survival response of calcareous, agglutinated, and thecate foraminifera was determined in two experiments at ~3.1 and 3.3 km water depth in Monterey Bay (California, USA). Approximately five weeks after initial seafloor CO2 release, in situ incubations of the live-dead indicator CellTracker Green were executed within seafloor-emplaced pushcores. Experimental treatments included direct exposure to CO2 hydrate, two levels of lesser exposure adjacent to CO2 hydrate, and controls, which were far removed from the CO2 hydrate release. Results indicate that survivorship rates of agglutinated and thecate foraminifera were not significantly impacted by direct exposure but the survivorship of calcareous foraminifera was significantly lower in direct exposure treatments compared to controls. Observations suggest that, if large scale CO2 sequestration is enacted on the deep-sea floor, survival of two major groups of this prevalent protistan taxon will likely not be severely impacted, while calcareous foraminifera will face considerable challenges to maintain their benthic populations in areas directly exposed to CO2 hydrate.
  • Article
    Corrigendum to "A culture-based calibration of benthic foraminiferal paleotemperature proxies: δ18O and Mg/Ca results" published in Biogeosciences, 7, 1335–1347, 2010
    (Copernicus Publications on behalf of the European Geosciences Union, 2011-06-10) Filipsson, Helena L. ; Bernhard, Joan M. ; Lincoln, Sara ; McCorkle, Daniel C.
  • Preprint
    Benthic foraminiferal ultrastructural alteration induced by heavy metals
    ( 2017-10) Frontalini, Fabrizio ; Nardelli, Maria Pia ; Curzi, Davide ; Martín-González, Ana ; Sabbatini, Anna ; Negri, Alessandra ; Losada, Maria Teresa ; Gobbi, Pietro ; Coccioni, Rodolfo ; Bernhard, Joan M.
    Heavy metals are known to cause deleterious effects on biota because of their toxicity, persistence and bioaccumulation. Here, we briefly document the ultrastructural changes observed in the miliolid foraminifer Pseudotriloculina rotunda (d'Orbigny in Schlumberger, 1893) and in the perforate calcareous species Ammonia parkinsoniana (d'Orbigny, 1839) induced by exposure to one of three heavy metals (zinc, lead, or mercury). The exposure of these two benthic foraminiferal species to the selected heavy metals appear to promote cytological alterations and organelle degeneration. These alterations include a thickening of the inner organic lining, an increase in number and size of lipid droplets, mitochondrial degeneration, and degradation vacuoles and residual body proliferation. Some of these alterations, including the thickening of the inner organic lining and the proliferation of lipids, might represent defense mechanisms against heavy metal-induced stress.
  • Article
    Keystone Arctic paleoceanographic proxy association with putative methanotrophic bacteria
    (Nature Publishing Group, 2018-07-13) Bernhard, Joan M. ; Panieri, Giuliana
    Foraminifera in sediments exposed to gas-hydrate dissociation are not expected to have cellular adaptations that facilitate inhabitation of chemosynthesis-based ecosystems because, to date, there are no known endemic seep foraminifera. To establish if foraminifera inhabit sediments impacted by gas-hydrate dissociation, we examined the cellular ultrastructure of Melonis barleeanus (Williamson, 1858) from the Vestnesa gas hydrate province (Arctic Ocean, west of Svalbard at ~79 °N; ~1200-m depth; n = 4). From sediments with gas hydrate indicators, living M. barleeanus had unusual pore plugs composed of a thick, fibrous meshwork; mitochondria were concentrated at the cell periphery, under pore plugs. While there was no evidence of endosymbioses with prokaryotes, most M. barleeanus specimens were associated with what appear to be Type I methanotrophic bacteria. One foraminifer had a particularly large bolus of these microbes concentrated near its aperture. This is the first documented instance of bona fide living M. barleeanus in gas-hydrate sediments and first documentation of a foraminifer living in close association with putative methanotrophs. Our observations have implications to paleoclimate records utilizing this foundational foraminiferal species.
  • Preprint
    Ultrastructure and distribution of kleptoplasts in benthic foraminifera from shallow-water (photic) habitats
    ( 2017-10) Jauffrais, Thierry ; LeKieffre, Charlotte ; Koho, Karoliina ; Tsuchiya, Masashi ; Schweizer, Magali ; Bernhard, Joan M. ; Meibom, Anders ; Geslin, Emmanuelle
    Assimilation, sequestration and maintenance of foreign chloroplasts inside an organism is termed “chloroplast sequestration” or “kleptoplasty”. This phenomenon is known in certain benthic foraminifera, in which such kleptoplasts can be found both intact and functional, but with different retention times depending on foraminiferal species. In the present study, seven species of benthic foraminifera (Haynesina germanica, Elphidium williamsoni, E. selseyense, E. oceanense, E. aff. E. crispum, Planoglabratella opercularis and Ammonia sp.) were collected from shallow-water benthic habitats and examined with transmission electron microscope (TEM) for cellular ultrastructure to ascertain attributes of kleptoplasts. Results indicate that all these foraminiferal taxa actively obtain kleptoplasts but organized them differently within their endoplasm. In some species, the kleptoplasts were evenly distributed throughout the endoplasm (e.g., H. germanica, E. oceanense, Ammonia sp.), whereas other species consistently had plastids distributed close to the external cell membrane (e.g., Elphidium williamsoni, E. selseyense, P. opercularis). Chloroplast degradation also seemed to differ between species, as many degraded plastids were found in Ammonia sp. and E. oceanense compared to other investigated species. Digestion ability, along with different feeding and sequestration strategies may explain the differences in retention time between taxa. Additionally, the organization of the sequestered plastids within the endoplasm may also suggest behavioral strategies to expose and/or protect the sequestered plastids to/from light and/or to favor gas and/or nutrient exchange with their surrounding habitats.
  • Article
    Deposit-feeding of Nonionellina labradorica (foraminifera) from an Arctic methane seep site and possible association with a methanotroph
    (European Geosciences Union, 2022-08-30) Schmidt, Christiane ; Geslin, Emmanuelle ; Bernhard, Joan M. ; LeKieffre, Charlotte ; Svenning, Mette Marianne ; Roberge, Hélène ; Schweizer, Magali ; Panieri, Giuliana
    Several foraminifera are deposit feeders that consume organic detritus (dead particulate organic material with entrained bacteria). However, the role of such foraminifera in the benthic food web remains understudied. Foraminifera feeding on methanotrophic bacteria, which are 13C-depleted, may cause negative cytoplasmic and/or calcitic δ13C values. To test whether the foraminiferal diet includes methanotrophs, we performed a short-term (20 h) feeding experiment with Nonionellina labradorica from an active Arctic methane-emission site (Storfjordrenna, Barents Sea) using the marine methanotroph Methyloprofundus sedimenti and analysed N. labradorica cytology via transmission electron microscopy (TEM). We hypothesised that M. sedimenti would be visible post-experiment in degradation vacuoles, as evidenced by their ultrastructure. Sediment grains (mostly clay) occurred inside one or several degradation vacuoles in all foraminifers. In 24 % of the specimens from the feeding experiment degradation vacuoles also contained bacteria, although none could be confirmed to be the offered M. sedimenti. Observations of the apertural area after 20 h incubation revealed three putative methanotrophs, close to clay particles, based on bacterial ultrastructural characteristics. Furthermore, we noted the absence of bacterial endobionts in all examined N. labradorica but confirmed the presence of kleptoplasts, which were often partially degraded. In sum, we suggest that M. sedimenti can be consumed via untargeted grazing in seeps and that N. labradorica can be generally classified as a deposit feeder at this Arctic site.
  • Dataset
    CTD data from coring cruise R/V Oceanus OC424-1 on the continental margin of the South Atlantic Bight and the Bahamas
    ( 2006-05) Bernhard, Joan M. ; McCorkle, Daniel C.
    These CTD data were collected during a twelve-day cruise in May 2006 on the R/V Oceanus (OC-424-1; Woods Hole, MA – Charleston, SC). The principal goal of the cruise was to collect foraminiferal “livestock” for multiple-carbonate-chemistry culturing experiments. The main purpose of the CTD casts was to collect bottom water, which was used for shipboard sieving of the sediment samples. We also sampled bottom water for comparison with the shell chemistry of benthic foraminiferal field specimens. This included samples for oxygen, Dissolved Inorganic Carbon and Alkalinity to define bottom water carbonate chemistry and calcite saturation state, the d13C of DIC, and the d18O of water; the University of South Carolina group sampled for minor and trace elements, too. The CTD data archived here were not processed or subjected to any quality control evaluation.
  • Dataset
    Cruise track (1-min fixes; from R2R) from R/V F.G. Walton Smith cruise WS1005 from Miami to the Bahamas in 2010
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2019-11-12) Bernhard, Joan M.
    1-minute resolution navigation from the WS1005 cruise aboard the R/V F.G. Walton Smith from 18 March to 24 March 2010. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at:
  • Article
    Effects of lead pollution on Ammonia parkinsoniana (foraminifera) : ultrastructural and microanalytical approaches
    (PAGEPress, 2015-01-30) Frontalini, Fabrizio ; Curzi, Davide ; Giordano, Francesco M. ; Bernhard, Joan M. ; Falcieri, E. ; Coccioni, Rodolfo
    The responses of Ammonia parkinsoniana (Foraminifera) exposed to different concentrations of lead (Pb) were evaluated at the cytological level. Foraminifera-bearing sediments were placed in mesocosms that were housed in aquaria each with seawater of a different lead concentration. On the basis of transmission electron microscopy and environmental scanning electron microscopy coupled with energy dispersive spectrometer analyses, it was possible to recognize numerous morphological differences between untreated (i.e., control) and treated (i.e., lead enrichment) specimens. In particular, higher concentrations of this pollutant led to numerical increase of lipid droplets characterized by a more electron-dense core, proliferation of residual bodies, a thickening of the organic lining, mitochondrial degeneration, autophagosome proliferation and the development of inorganic aggregates. All these cytological modifications might be related to the pollutant-induced stress and some of them such as the thickening of organic lining might suggest a potential mechanism of protection adopted by foraminifera.
  • Dataset
    Scientific sampling event log from R/V Endeavor cruise EN524 along the continental shelf of New England in 2013 (OA, Hypoxia and Warming project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2019-11-06) Bernhard, Joan M.
    Scientific sampling event log from R/V Endeavor cruise EN524 along the continental shelf of New England in 2013. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at:
  • Article
    And on top of all that… coping with ocean acidification in the midst of many stressors
    (The Oceanography Society, 2015-06) Breitburg, Denise L. ; Salisbury, Joseph E. ; Bernhard, Joan M. ; Cai, Wei-Jun ; Dupont, Sam ; Doney, Scott C. ; Kroeker, Kristy J. ; Levin, Lisa A. ; Long, W. Christopher ; Milke, Lisa M. ; Miller, Seth H. ; Phelan, Beth ; Passow, Uta ; Seibel, Brad A. ; Todgham, Anne E. ; Tarrant, Ann M.
    Oceanic and coastal waters are acidifying due to processes dominated in the open ocean by increasing atmospheric CO2 and dominated in estuaries and some coastal waters by nutrient-fueled respiration. The patterns and severity of acidification, as well as its effects, are modified by the host of stressors related to human activities that also influence these habitats. Temperature, deoxygenation, and changes in food webs are particularly important co-stressors because they are pervasive, and both their causes and effects are often mechanistically linked to acidification. Development of a theoretical underpinning to multiple stressor research that considers physiological, ecological, and evolutionary perspectives is needed because testing all combinations of stressors and stressor intensities experimentally is impossible. Nevertheless, use of a wide variety of research approaches is a logical and promising strategy for improving understanding of acidification and its effects. Future research that focuses on spatial and temporal patterns of stressor interactions and on identifying mechanisms by which multiple stressors affect individuals, populations, and ecosystems is critical. It is also necessary to incorporate consideration of multiple stressors into management, mitigation, and adaptation to acidification and to increase public and policy recognition of the importance of addressing acidification in the context of the suite of other stressors with which it potentially interacts.
  • Article
    Impacts of multiple stressors on a benthic foraminiferal community: a long-term experiment assessing response to ocean acidification, hypoxia and warming
    (Frontiers Media, 2021-04-22) Bernhard, Joan M. ; Wit, Johannes C. ; Starczak, Victoria R. ; Beaudoin, David J. ; Phalen, William G. ; McCorkle, Daniel C.
    Ocean chemistry is changing as a result of human activities. Atmospheric carbon dioxide (CO2) concentrations are increasing, causing an increase in oceanic pCO2 that drives a decrease in oceanic pH, a process called ocean acidification (OA). Higher CO2 concentrations are also linked to rising global temperatures that can result in more stratified surface waters, reducing the exchange between surface and deep waters; this stronger stratification, along with nutrient pollution, contributes to an expansion of oxygen-depleted zones (so called hypoxia or deoxygenation). Determining the response of marine organisms to environmental changes is important for assessments of future ecosystem functioning. While many studies have assessed the impact of individual or paired stressors, fewer studies have assessed the combined impact of pCO2, O2, and temperature. A long-term experiment (∼10 months) with different treatments of these three stressors was conducted to determine their sole or combined impact on the abundance and survival of a benthic foraminiferal community collected from a continental-shelf site. Foraminifera are well suited to such study because of their small size, relatively rapid growth, varied mineralogies and physiologies. Inoculation materials were collected from a ∼77-m deep site south of Woods Hole, MA. Very fine sediments (<53 μm) were used as inoculum, to allow the entire community to respond. Thirty-eight morphologically identified taxa grew during the experiment. Multivariate statistical analysis indicates that hypoxia was the major driving factor distinguishing the yields, while warming was secondary. Species responses were not consistent, with different species being most abundant in different treatments. Some taxa grew in all of the triple-stressor samples. Results from the experiment suggest that foraminiferal species’ responses will vary considerably, with some being negatively impacted by predicted environmental changes, while other taxa will tolerate, and perhaps even benefit, from deoxygenation, warming and OA.
  • Article
    Prevalence of partnerships between bacteria and ciliates in oxygen-depleted marine water columns
    (Frontiers Media, 2012-09-19) Orsi, William D. ; Charvet, Sophie ; Vd'acny, Peter ; Bernhard, Joan M. ; Edgcomb, Virginia P.
    Symbioses between Bacteria, Archaea, and Eukarya in deep-sea marine environments represent a means for eukaryotes to exploit otherwise inhospitable habitats. Such symbioses are abundant in many low-oxygen benthic marine environments, where the majority of microbial eukaryotes contain prokaryotic symbionts. Here, we present evidence suggesting that in certain oxygen-depleted marine water-column habitats, the majority of microbial eukaryotes are also associated with prokaryotic cells. Ciliates (protists) associated with bacteria were found to be the dominant eukaryotic morphotype in the haloclines of two different deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea. These findings are compared to associations between ciliates and bacteria documented from the permanently anoxic waters of the Cariaco Basin (Caribbean Sea). The dominance of ciliates exhibiting epibiotic bacteria across three different oxygen-depleted marine water column habitats suggests that such partnerships confer a fitness advantage for ciliates in these environments.
  • Preprint
    Ultrastructural observations on prokaryotic associates of benthic foraminifera : food, mutualistic symbionts, or parasites?
    ( 2017-09) Bernhard, Joan M. ; Tsuchiya, Masashi ; Nomaki, Hidetaka
    Because prokaryotes (Eubacteria, Archaea) are ubiquitous in the marine realm, it may not be surprising that they are important to the diet of at least some foraminifera. Over recent decades, Transmission Electron Microscopy (TEM) has revealed that, at the ultrastructural level, additional intimate relationships exist between prokaryotes and foraminifera. For example, the cytoplasm of a variety of benthic foraminiferal species contains intact prokaryotes. Other benthic foraminiferal species support prokaryotic populations on their exterior. Some of these prokaryote-foraminifera associations are sufficiently consistent to be considered symbioses. Symbiotic relationships include beneficial associations (mutualism; commensalism) to detrimental associations (parasitism). Here, we provide a synopsis of known foraminiferal- prokaryotic symbioses and TEM micrographs illustrating many specific associations. We further comment on and illustrate additional interactions such as bacterial scavenging on foraminifera and foraminiferal feeding on prokaryotes. Documenting and understanding all of these microbial interactions will contribute to a more comprehensive knowledge of benthic marine ecology and biology.
  • Dataset
    CTD data from coring cruise R/V Cape Hatteras CH1605 on the continental margin of the South Atlantic Bight and the Bahamas
    ( 2005-06) Bernhard, Joan M. ; McCorkle, Daniel C.
    These CTD data were collected during a nine-day cruise in early June 2005 on the R/V Cape Hatteras (CH09-05; Beaufort, NC – Beaufort, NC). The principal goal of the cruise was to collect foraminiferal “livestock” for multiple-carbonate-chemistry culture experiments. The main purpose of the CTD casts was to collect bottom water, which was used for shipboard sieving of the sediment samples. We also sampled bottom water for comparison with the shell chemistry of benthic foraminiferal field specimens. This included samples for oxygen, Dissolved Inorganic Carbon and Alkalinity to define bottom water carbonate chemistry and calcite saturation state, the d13C of DIC, and the d18O of water; the University of South Carolina group sampled for minor and trace elements, too. We also collected two CTD-rosette profiles to provide samples to Ms. Angie Knapp at Princeton University, for use in isotopic studies of the marine N cycle. The CTD data archived here were not processed or subjected to any quality control evaluation.
  • Preprint
    Tolerance of allogromiid Foraminifera to severely elevated carbon dioxide concentrations : implications to future ecosystem functioning and paleoceanographic interpretations
    ( 2007-12-21) Bernhard, Joan M. ; Mollo-Christensen, Elizabeth ; Eisenkolb, Nadine ; Starczak, Victoria R.
    Increases in the partial pressure of carbon dioxide (pCO2) in the atmosphere will significantly affect a wide variety of terrestrial fauna and flora. Because of tight atmospheric-oceanic coupling, shallow-water marine species are also expected to be affected by increases in atmospheric carbon dioxide concentrations. One proposed way to slow increases in atmospheric pCO2 is to sequester CO2 in the deep sea. Thus, over the next few centuries marine species will be exposed to changing seawater chemistry caused by ocean-atmospheric exchange and/or deep-ocean sequestration. This initial case study on one allogromiid foraminiferal species (Allogromia laticollaris) was conducted to begin to ascertain the effect of elevated pCO2 on benthic Foraminifera, which are a major meiofaunal constituent of shallow- and deep-water marine communities. Cultures of this thecate foraminiferan protist were used for 10-14-day experiments. Experimental treatments were executed in an incubator that controlled CO2 (15 000; 30 000; 60 000; 90 000; 200 000 ppm), temperature and humidity; atmospheric controls (i.e., ~375 ppm CO2) were executed simultaneously. Although the experimental elevated pCO2 values are far above foreseeable surface water pCO2, they were selected to represent the spectrum of conditions expected for the benthos if deep-sea CO2 sequestration becomes a reality. Survival was assessed in two independent ways: pseudopodial presence/absence and measurement of adenosine triphosphate (ATP), which is an indicator of cellular energy. Substantial proportions of A. laticollaris populations survived 200 000 ppm CO2 although the mean of the median [ATP] of survivors was statistically lower for this treatment than for that of atmospheric control specimens. After individuals that had been incubated in 200 000 ppm CO2 for 12 days were transferred to atmospheric conditions for ~24 hours, the [ATP] of live specimens (survivors) approximated those of the comparable atmospheric control treatment. Incubation in 200 000 ppm CO2 also resulted in reproduction by some individuals. Results suggest that certain Foraminifera are able to tolerate deep-sea CO2 sequestration and perhaps thrive as a result of elevated pCO2 that is predicted for the next few centuries, in a high-pCO2 world. Thus, allogromiid foraminiferal “blooms” may result from climate change. Furthermore, because allogromiids consume a variety of prey, it is likely that they will be major players in ecosystem dynamics of future coastal sedimentary environments.
  • Preprint
    Innovative TEM-coupled approaches to study foraminiferal cells
    ( 2017-10) Nomaki, Hidetaka ; LeKieffre, Charlotte ; Escrig, Stéphane ; Meibom, Anders ; Yagyu, Shinsuke ; Richardson, Elizabeth A. ; Matsuzaki, Takuya ; Murayama, Masafumi ; Geslin, Emmanuelle ; Bernhard, Joan M.
    Transmission electron microscope (TEM) observation has revealed much about the basic cell biology of foraminifera. Yet, there remains much we do not know about foraminiferal cytology and physiology, especially for smaller benthic foraminifera, which inhabit a wide range of habitats. Recently, some TEM-coupled approaches have been developed to study correlative foraminiferal ecology and physiology in detail: Fluorescently Labeled Embedded Core (FLEC)-TEM for observing foraminiferal life-position together with their cytoplasmic ultrastructure, micro-X-ray computed tomography (CT)-TEM for observing and reconstructing foraminiferal cytoplasm in three dimensions (3D), and TEM-Nanometer-scale secondary ion mass spectrometry (NanoSIMS) for mapping of elemental and isotopic compositions at sub-micrometer resolutions with known ultrastructure. In this contribution, we review and illustrate these recent advances of TEM-coupled methods.