Ultrastructural observations on prokaryotic associates of benthic foraminifera : food, mutualistic symbionts, or parasites?

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Marine Micropaleontology 138 (2018): 33-45, doi:10.1016/j.marmicro.2017.09.001.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.JMB’s contributions were funded by US NSF funding over many years, most recently NSF grant OCE-1634469, as well as the WHOI Robert W. Morse Chair for Excellence in Oceanography and The Investment in Science Fund at WHOI. MT and HN’s contributions were funded by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (no. 24340131 to MT and no. 22740340 to HN)

An ectobiont-bearing foraminiferan, Bolivina pacifica, that inhabits microxic pore waters : cell-biological and paleoceanographic insights

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Environmental Microbiology 12 (2010): 2107-2119, doi:10.1111/j.1462-2920.2009.02073.x.The presence of tests (shells) in foraminifera could be taken as an indicator that this protist taxon is unlikely to possess ectosymbionts. Here, however, we describe an association between Bolivina pacifica, a foraminiferan with a calcareous test, and a rod-shaped microbe (bacterium or archaeon) that is directly associated with the pores of the foraminiferan’s test. In addition to these putative ectosymbionts, B. pacifica has previously undescribed cytoplasmic plasma membrane invaginations (PMIs). These adaptations (i.e., PMIs, ectobionts), along with the clustering of mitochondria under the pores and at the cell periphery, suggest active exchange between the host and ectobiont. The B. pacifica specimens examined were collected from sediments overlain by oxygen-depleted bottom waters (0.7 μM) of the Santa Barbara Basin (SBB; California, USA). An ultrastructural comparison between B. pacifica from the SBB and a congener (Bolivina cf. B. lanceolata) collected from well-oxygenated sediments (Florida Keys) suggests that PMIs, ectobionts, and peripherally distributed mitochondria are all factors that promote inhabitation of microxic environments by B. pacifica. The calcitic δ13C signatures of B. pacifica and a of co-occurring congener (B. argentea) that lacks ectobionts differ by >1.5‰, raising the possibility that the presence of ectobionts can affect incorporation of paleoceanographic proxies.This work was supported by a W. Storrs Cole Memorial Research Award through the Geological Society of America (to JMB), as well as by NASA Exobiology NRA-01-01-EXB-057 (to JMB), NSF MCB-0702491 (to JMB), and NSF DEB0445181 (to SSB and STG)

A short-term survival experiment assessing impacts of ocean acidification and hypoxia on the benthic foraminifer Globobulimina turgida

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Journal of Foraminiferal Research 46 (2016): 25-33, doi:10.2113/gsjfr.46.1.25.The oceans are absorbing increasing amounts of carbon dioxide (CO2) as a result of rising anthropogenic atmospheric CO2 emissions. This increase in oceanic CO2 leads to the lowering of seawater pH, which is known as ocean acidification (OA). Simultaneously, rising global temperatures, also linked to higher atmospheric CO2 concentrations, result in a more stratified surface ocean, reducing exchange between surface and deeper waters, leading to expansion of oxygen-limited zones (hypoxia). Numerous studies have investigated the impact of one or the other of these environmental changes (OA, hypoxia) on a wide variety of marine organisms, but few experimental studies focus on the simultaneous effects of these two stressors. Foraminifera are unicellular eukaryotes (protists) that live in virtually every marine environment and form an important link in the benthic food web. Here we present results of a short-term (3.5 week) study in which both CO2 (OA) and O2 (hypoxia) were manipulated to evaluate the influence of these parameters on the survival of the benthic foraminifer Globobulimina turgida. Elevated CO2 concentrations did not impact short-term survivorship of this species, and furthermore, G. turgida had higher survival percentages under hypoxic conditions (0.7 ml/l) than in well-aerated water, regardless of CO2 concentration.This research was supported by US NSF grant OCE-1219948 to JMB.2017-01-0

Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins

Background: The deep-sea hypersaline anoxic basins (DHABs) of the Mediterranean (water depth similar to 3500 m) are some of the most extreme oceanic habitats known. Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB haloclines and brines, loriciferans are the only metazoan reported to inhabit the anoxic DHAB brines. Our goal was to further investigate metazoan communities in DHAB haloclines and brines. Results: We report observations from sediments of three DHAB (Urania, Discovery, L'Atalante) haloclines, comparing these to observations from sediments underlying normoxic waters of typical Mediterranean salinity. Due to technical difficulties, sampling of the brines was not possible. Morphotype analysis indicates nematodes are the most abundant taxon; crustaceans, loriciferans and bryozoans were also noted. Among nematodes, Daptonema was the most abundant genus; three morphotypes were noted with a degree of endemicity. The majority of rRNA sequences were from planktonic taxa, suggesting that at least some individual metazoans were preserved and inactive. Nematode abundance data, in some cases determined from direct counts of sediments incubated in situ with CellTracker (TM) Green, was patchy but generally indicates the highest abundances in either normoxic control samples or in upper halocline samples; nematodes were absent or very rare in lower halocline samples. Ultrastructural analysis indicates the nematodes in L'Atalante normoxic control sediments were fit, while specimens from L'Atalante upper halocline were healthy or had only recently died and those from the lower halocline had no identifiable organelles. Loriciferans, which were only rarely encountered, were found in both normoxic control samples as well as in Discovery and L'Atalante haloclines. It is not clear how a metazoan taxon could remain viable under this wide range of conditions. Conclusions: We document a community of living nematodes in normoxic, normal saline deep-sea Mediterranean sediments and in the upper halocline portions of the DHABs. Occurrences of nematodes in mid-halocline and lower halocline samples did not provide compelling evidence of a living community in those zones. The possibility of a viable metazoan community in brines of DHABs is not supported by our data at this time

A culture-based calibration of benthic foraminiferal paleotemperature proxies : δ18O and Mg/Ca results

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 1335-1347, doi:10.5194/bg-7-1335-2010Benthic foraminifera were cultured for five months at four temperatures (4, 7, 14 and 21 °C) to establish the temperature dependence of foraminiferal calcite δ18O and Mg/Ca. Two Bulimina species (B. aculeata and B. marginata) were most successful in terms of calcification, adding chambers at all four temperatures and reproducing at 7 and 14 °C. Foraminiferal δ18O values displayed ontogenetic variations, with lower values in younger individuals. The δ18O values of adult specimens decreased with increasing temperature in all but the 4 °C treatment, exhibiting a relationship consistent with previous δ18O paleotemperature calibration studies. Foraminiferal Mg/Ca values, determined by laser ablation inductively coupled plasma mass spectrometry, were broadly consistent with previous Mg/Ca calibration studies, but extremely high values in the 4 °C treatment and higher than predicted values at two of the other three temperatures make it challenging to interpret these results.Funding was provided by US NSF OCE-0647899 to DCM and JMB, and by the Swedish Research Council (grant no 621-2005-4265), the Lamm Foundation, and the Engkvist Foundation to HLF. A Fulbright fellowship to HLF together with traveling grants from G¨oteborg University, the Crafoord Foundation, and the Royal Physiographic Society in Lund enabled HLF’s Postdoc stay and subsequent visits to WHOI

Corrigendum to "A culture-based calibration of benthic foraminiferal paleotemperature proxies: δ18O and Mg/Ca results" published in Biogeosciences, 7, 1335–1347, 2010

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 8 (2011): 1521, doi:10.5194/bg-8-1521-2011

Ocean acidification not likely to affect the survival and fitness of two temperate benthic foraminiferal species : results from culture experiments

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Cushman Foundation for Foraminiferal Research for personal use, not for redistribution. The definitive version was published in Journal of Foraminiferal Research 44 (2014): 341-351.Specimens of Bolivina argentea and Bulimina marginata, two widely distributed temperate benthic foraminiferal species, were cultured at constant temperature and controlled pCO2 (ambient, 1000 ppmv, and 2000 ppmv) for six weeks to assess the effect of elevated atmospheric CO2 concentrations on survival and fitness using Adenosine Triphosphate (ATP) analyses and on shell microfabric using high-resolution SEM and image analysis. To characterize the carbonate chemistry of the incubation seawater, total alkalinity and dissolved inorganic carbon were measured approximately every two weeks. Survival and fitness were not directly affected by elevated pCO2 and the concomitant decrease in seawater pH and calcite saturation states (Ωc), even when seawater was undersaturated with respect to calcite. These results differ from some previous observations that ocean acidification can cause a variety of effects on benthic foraminifera, including test dissolution, decreased growth, and mottling (loss of symbiont color in symbiont-bearing species), suggesting that the benthic foraminiferal response to ocean acidification may be species specific. If so, this implies that ocean acidification may lead to ecological winners and losers even within the same taxonomic group.This research was supported by NSF grants OCE-0647899 to DCM and JMB, OCE-0725966 to JMB and DCM, and OA-1219948 to JMB.2015-10-0

Prevalence of partnerships between bacteria and ciliates in oxygen-depleted marine water columns

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 3 (2012): 341, doi:10.3389/fmicb.2012.00341.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.This work was funded by NSF grant OCE-0849578 and to Virginia P. Edgcomb and Joan M. Bernhard, and OCE-1061774 to Virginia P. Edgcomb and Craig Taylor (WHOI)

Structured Multiple Endosymbiosis of Bacteria and Archaea in a Ciliate from Marine Sulfidic Sediments: A Survival Mechanism in Low Oxygen, Sulfidic Sediments?

Marine micro-oxic to sulfidic environments are sites of intensive biogeochemical cycling and elemental sequestration, where prokaryotes are major driving forces mediating carbon, nitrogen, sulfur, phosphorus, and metal cycles, important from both biogeochemical and evolutionary perspectives. Associations between single-celled eukaryotes and bacteria and/or archaea are common in such habitats. Here we describe a ciliate common in the micro-oxic to anoxic, typically sulfidic, sediments of Santa Barbara Basin (CA, USA). The ciliate is 95% similar to Parduzcia orbis (18S rRNA). Transmission electron micrographs reveal clusters of at least three different endobiont types organized within membrane-bound sub-cellular regions. Catalyzed reporter deposition–fluorescent in situ hybridization and 16S rRNA clone libraries confirm the symbionts include up to two sulfate reducers (Desulfobulbaceae, Desulfobacteraceae), a methanogen (Methanobacteriales), and possibly a Bacteroidete (Cytophaga) and a Type I methanotroph, suggesting synergistic metabolisms in this environment. This case study is discussed in terms of implications to biogeochemistry, and benthic ecology

Comparison of two methods to identify live benthic foraminifera : a test between Rose Bengal and CellTracker Green with implications for stable isotope paleoreconstructions

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography, 21 (2006): PA4210, doi:10.1029/2006PA001290.The conventional method to distinguish live from dead benthic foraminifers uses Rose Bengal, a stain that reacts with both live and dead cytoplasm. CellTracker Green CMFDA is a fluorogenic probe causing live cells to fluoresce after proper incubation. To determine the more accurate viability method, we conducted a direct comparison of Rose Bengal staining with CellTracker Green labeling. Eight multicore tops were analyzed from Florida Margin (SE United States; 248-751 m water depths), near Great Bahama Bank (259-766 m), and off the Carolinas (SE United States; 220 m, 920 m). On average, less than half the Rose Bengal-stained foraminifera were actually living when collected. Thus, while Rose Bengal can significantly overestimate abundance, combined analyses of CellTracker Green and Rose Bengal can provide insights on population dynamics and effects of episodic events. Initial stable isotope analyses indicate that the CellTracker Green method does not significantly affect these important paleoceanographic proxies.Funding for this research was provided by the National Science Foundation Research Experience for Undergraduates Program (grant #OCE-0139423; PI, D. McCorkle, WHOI) and NSF grants OCE-9911654 and OCE-0351029