Toner
Brandy M.
Toner
Brandy M.
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PreprintNear-field iron and carbon chemistry of non-buoyant hydrothermal plume particles, Southern East Pacific Rise 15°S( 2018-01) Hoffman, Colleen L. ; Nicholas, Sarah L. ; Ohnemus, Daniel C. ; Fitzsimmons, Jessica N. ; Sherrell, Robert M. ; German, Christopher R. ; Heller, Maija Iris ; Lee, Jong-mi ; Lam, Phoebe J. ; Toner, Brandy M.
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PreprintIron persistence in a distal hydrothermal plume supported by dissolved–particulate exchange( 2017-01) Fitzsimmons, Jessica N. ; John, Seth G. ; Marsay, Christopher M. ; Hoffman, Colleen L. ; Nicholas, Sarah L. ; Toner, Brandy M. ; German, Christopher R. ; Sherrell, Robert M.Hydrothermally-sourced dissolved metals have been recorded in all ocean basins. In the oceans’ largest known hydrothermal plume, extending westward across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4000 km from the source. Both dissolved and particulate iron deepen by more than 350 m relative to 3He – a non-reactive tracer of hydrothermal input – crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5-10 m year-1. Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe(III) oxyhydroxides, while dissolved iron consists of nanoparticulate Fe(III) oxyhydroxides and an organically-complexed iron phase. The descent of plume dissolved iron is best explained by reversible exchange onto slowly sinking particles, likely mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles.
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ArticleBiogeochemical processes at hydrothermal vents : microbes and minerals, bioenergetics, and carbon fluxes(The Oceanography Society, 2012-03) Holden, James F. ; Breier, John A. ; Rogers, Karyn L. ; Schulte, Mitchell D. ; Toner, Brandy M.Hydrothermal vents are among the most biologically active regions of the deep ocean. However, our understanding of the limits of life in this extreme environment, the extent of biogeochemical transformation that occurs in the crust and overlying ocean, and the impact of vent life on regional and global ocean chemistry is in its infancy. Recently, scientific studies have expanded our view of how vent microbes gain metabolic energy at vents through their use of dissolved chemicals and minerals contained in ocean basalts, seafloor sulfide deposits, and hydrothermal plumes and, in turn, how they catalyze chemical and mineral transformations. The scale of vent environments and the difficulties inherent in the study of life above, on, and below the deep seafloor have led to the development of geochemical and bioenergetic models. These models predict habitability and biological activity based on the chemical composition of hydrothermal fluids, seawater, and the surrounding rock, balanced by the physiological energy demand of cells. This modeling, coupled with field sampling for ground truth and discovery, has led to a better understanding of how hydrothermal vents affect the ocean and global geochemical cycles, and how they influence our views of life on the early Earth and the search for life beyond our own planet.
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ArticleMeasuring the form of iron in hydrothermal plume particles(The Oceanography Society, 2012-03) Toner, Brandy M. ; Marcus, Matthew A. ; Edwards, Katrina J. ; Rouxel, Olivier J. ; German, Christopher R.The global mid-ocean ridge (MOR) system is a 60,000 km submarine volcanic mountain range that crosses all of the major ocean basins on Earth. Along the MOR, subseafloor seawater circulation exchanges heat and elements between the oceanic crust and seawater. One of the elements released through this venting process is iron. The amount of iron released by hydrothermal venting to the ocean per year (called a flux) is similar in magnitude to that in global riverine runoff (Elderfield and Schultz, 1996). Until recently, measurements and modeling activities to understand the contribution of hydrothermal iron to the ocean budget have been largely neglected. It was thought that hydrothermal iron was removed completely from seawater by precipitation of iron-bearing minerals within plumes and then deposited at the seafloor close to vent sites. With this assumption in place, the contribution of hydrothermal fluxes to the ocean budget was considered negligible. Recent work, however, questions the validity of that assumption, and leads to what we call the "leaky vent" hypothesis. Our goal is to measure the forms of iron, known as speciation, present in hydrothermal plume particles to better understand the bioavailability, geochemical reactivity, and transport properties of hydrothermal iron in the ocean.
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PreprintSulfur oxidation genes in diverse deep-sea viruses( 2014-04) Anantharaman, Karthik ; Duhaime, Melissa B. ; Breier, John A. ; Wendt, Kathleen A. ; Toner, Brandy M. ; Dick, Gregory J.Viruses are the most abundant biological entities in the oceans and a pervasive cause of mortality of microorganisms that drive biogeochemical cycles. Although the ecological and evolutionary impacts of viruses on marine phototrophs are well-recognized, little is known about their impact on ubiquitous marine lithotrophs. Here we report 18 genome sequences of double-stranded DNA viruses that putatively infect widespread sulfur-oxidizing bacteria. Fifteen of these viral genomes contain auxiliary metabolic genes for the alpha and gamma subunits of reverse dissimilatory sulfite reductase (rdsr). This enzyme oxidizes elemental sulfur, which is abundant in the hydrothermal plumes studied here. Our findings implicate viruses as a key agent in the sulfur cycle and as a reservoir of genetic diversity for bacterial enzymes that underpin chemosynthesis in the deep oceans.
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ArticleUltra-diffuse hydrothermal venting supports Fe-oxidizing bacteria and massive umber deposition at 5000 m off Hawaii(Nature Publishing Group, 2011-05-05) Edwards, Katrina J. ; Glazer, Brian T. ; Rouxel, Olivier J. ; Bach, Wolfgang ; Emerson, David ; Toner, Brandy M. ; Chan, Clara S. ; Tebo, Bradley M. ; Staudigel, Hubert ; Moyer, Craig L.A novel hydrothermal field has been discovered at the base of Lōihi Seamount, Hawaii, at 5000 mbsl. Geochemical analyses demonstrate that ‘FeMO Deep’, while only 0.2 °C above ambient seawater temperature, derives from a distal, ultra-diffuse hydrothermal source. FeMO Deep is expressed as regional seafloor seepage of gelatinous iron- and silica-rich deposits, pooling between and over basalt pillows, in places over a meter thick. The system is capped by mm to cm thick hydrothermally derived iron-oxyhydroxide- and manganese-oxide-layered crusts. We use molecular analyses (16S rDNA-based) of extant communities combined with fluorescent in situ hybridizations to demonstrate that FeMO Deep deposits contain living iron-oxidizing Zetaproteobacteria related to the recently isolated strain Mariprofundus ferroxydans. Bioenergetic calculations, based on in-situ electrochemical measurements and cell counts, indicate that reactions between iron and oxygen are important in supporting chemosynthesis in the mats, which we infer forms a trophic base of the mat ecosystem. We suggest that the biogenic FeMO Deep hydrothermal deposit represents a modern analog for one class of geological iron deposits known as ‘umbers’ (for example, Troodos ophilolites, Cyprus) because of striking similarities in size, setting and internal structures.
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ArticleOcean system science to inform the exploration of ocean worlds(Oceanography Society, 2022-05-23) German, Christopher R. ; Blackman, Donna K. ; Fisher, Andrew T. ; Girguis, Peter R. ; Hand, Kevin P. ; Hoehler, Tori M. ; Huber, Julie A. ; Marshall, John C. ; Pietro, Kathryn R. ; Seewald, Jeffrey S. ; Shock, Everett ; Sotin, Christophe ; Thurnherr, Andreas M. ; Toner, Brandy M.Ocean worlds provide fascinating opportunities for future ocean research. They allow us to test our understanding of processes we consider fundamental to Earth’s ocean and simultaneously provide motivation to explore our ocean further and develop new technologies to do so. In parallel, ocean worlds research offers opportunities for ocean scientists to provide meaningful contributions to novel investigations in the coming decades that will search for life beyond Earth. Key to the contributions that oceanographers can make to this field is that studies of all other ocean worlds remain extremely data limited. Here, we describe an approach based on ocean systems science in which theoretical modeling can be used, in concert with targeted laboratory experimentation and direct observations in Earth’s ocean, to predict what processes (including those essential to support life) might be occurring on other ocean worlds. In turn, such an approach would help identify new technologies that might be required for future space missions as well as appropriate analog studies that could be conducted on Earth to develop and validate such technologies. Our approach is both integrative and interdisciplinary and considers multiple domains, from processes active in the subseafloor to those associated with ocean-ice feedbacks.
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PreprintMicrobial iron uptake as a mechanism for dispersing iron from deep-sea hydrothermal vents( 2014-01) Li, Meng ; Toner, Brandy M. ; Baker, Brett J. ; Breier, John A. ; Sheik, Cody S. ; Dick, Gregory J.Deep-sea hydrothermal vents are a significant source of oceanic iron. Although hydrothermal iron rapidly precipitates as inorganic minerals upon mixing with seawater, it can be stabilized by organic matter and dispersed more widely than previously recognized. The nature and source of this organic matter is unknown. Here we show that microbial genes involved in cellular iron uptake are highly expressed in the Guaymas Basin deep-sea hydrothermal plume. The nature of these microbial iron transporters, taken together with the low concentration of dissolved iron and abundance of particulate iron in the plume, indicates that iron minerals are the target for this microbial scavenging and uptake. Our findings indicate that cellular iron uptake is a major process in plume microbial communities and suggest new mechanisms for generating Fe-C complexes. This “microbial iron pump” could represent an important mode of converting hydrothermal iron into bioavailable forms that can be dispersed through the oceans.