57 research outputs found
Output from the PISCES Cobalt biogeochemical ocean model
No full textOutput from the PISCES biogeochemical model used in Hawco et al. 2020 PNAS. This model was originally developed and published in Tagliabue A, et al. (2018) [The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model. Global Biogeochem Cycles 32(4):594–616.] but with the base model modified as described by Aumont O, et al. (2017) [Variable reactivity of particulate organic matter in a global ocean biogeochemical model. Biogeosciences 14(9):2321–2341.]. All fields are annual averages.
For more information see www.pnas.org/cgi/doi/10.1073/pnas.200139311
A dissolved cobalt plume in the oxygen minimum zone of the eastern tropical South Pacific
No full textCobalt is a nutrient to phytoplankton, but knowledge about its biogeochemical cycling is limited, especially in the Pacific Ocean. Here, we report sections of dissolved cobalt and labile dissolved cobalt from the US GEOTRACES GP16 transect in the South Pacific. The cobalt distribution is closely tied to the extent and intensity of the oxygen minimum zone in the eastern South Pacific with highest concentrations measured at the oxycline near the Peru margin. Below 200 m, remineralization and circulation produce an inverse relationship between cobalt and dissolved oxygen that extends throughout the basin. Within the oxygen minimum zone, elevated concentrations of labile cobalt are generated by input from coastal sources and reduced scavenging at low O2. As these high cobalt waters are upwelled and advected offshore, phytoplankton export returns cobalt to low-oxygen water masses underneath. West of the Peru upwelling region, dissolved cobalt is less than 10 pM in the euphotic zone and strongly bound by organic ligands. Because the cobalt nutricline within the South Pacific gyre is deeper than in oligotrophic regions in the North and South Atlantic, cobalt involved in sustaining phytoplankton productivity in the gyre is heavily recycled and ultimately arrives from lateral transport of upwelled waters from the eastern margin. In contrast to large coastal inputs, atmospheric deposition and hydrothermal vents along the East Pacific Rise appear to be minor sources of cobalt. Overall, these results demonstrate that oxygen biogeochemistry exerts a strong influence on cobalt cycling.National Science Foundation (U.S.) (Award OCE-1237011
The cobalt cycle in the tropical Pacific Ocean
No full textThesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.Includes bibliographical references.Although over a dozen elements are needed to support phytoplankton growth, only a few are considered to be growth-limiting. As the central atom in vitamin B12, cobalt is crucial for metabolism, but its status as a limiting nutrient is uncertain. This thesis investigates the geochemical controls on oceanic cobalt scarcity and their biological consequences. Analysis of over 1000 samples collected in the Tropical Pacific Ocean reveals a dissolved cobalt distribution that is strongly coupled to dissolved oxygen, with peak concentrations where oxygen is lowest. Large cobalt plumes within anoxic waters are maintained by three processes: 1) a cobalt supply from organic matter remineralization, 2) an amplified sedimentary source from oxygen-depleted coastlines, and 3) low-oxygen inhibition of manganese oxidation, which scavenges cobalt from the water column. Rates of scavenging are calculated from a global synthesis of recent GEOTRACES data and agree with cobalt accumulation rates in pelagic sediments. Because both sources and sinks are tied to the extent of oxygen minimum zones, oceanic cobalt inventories are likely dynamic on the span of decades. Despite extremely low cobalt in the South Pacific gyre, the cyanobacterium Prochlorococcus thrives. Minimum cobalt and iron requirements of a Prochlorococcus strain isolated from the Equatorial Pacific are quantified. Cobalt quotas are related to demand for ribonucleotide reductase and methionine synthase enzymes, which catalyze critical steps in DNA and protein biosynthesis, respectively. Compared to other cyanobacteria, a streamlined metal physiology makes Prochlorococcus susceptible to competitive inhibition of cobalt uptake by low levels of zinc. Although phytoplankton in the Equatorial Pacific are subject to chronic iron-limitation, widespread cobalt scarcity and vulnerability to zinc inhibition observed in culture imply that wild Prochlorococcus are not far from a cobalt-limitation threshold.by Nicholas James Hawco.Ph. D
Iron and Cobalt Limitation in Atlantic Prochlorococcus MIT9301
No full textABSTRACT
Prochlorococcus is an abundant marine microorganism playing a vital role in the Earth’s carbon cycle and therefore climate. This organism is a cyanobacteria meaning it obtains energy through photosynthesis. A large portion of the ocean’s phytoplankton populations are limited by low concentrations of trace metals such as iron and cobalt. Future climate change will likely alter ocean circulation and supply of trace metals to the surface ocean, and may impact Prochlorococcus populations, which can affect marine food webs. We only have information on iron and cobalt requirements for a few strains of Prochlorococcus. Therefore, we performed culturing experiments to understand the growth and decay of Prochlorococcus in a lab environment with changes in levels of iron and cobalt. Iron limitation on Atlantic Prochlorococcus did not have a significant impact on growth rates, while cobalt limitation experiments did significantly impact the growth of these phytoplankton when lowered. The growth rates resulting from these experiments can be used to model future changes in Prochlorococcus populations as the impacts of climate change become more prevalent.
Keywords: Prochlorococcus, trace metal, cobalt, iron, growth rate, limitationProchlorococcus is an abundant marine microorganism playing a vital role in the Earth’s carbon cycle and therefore climate. This organism is a cyanobacteria meaning it obtains energy through photosynthesis. A large portion of the ocean’s phytoplankton populations are limited by low concentrations of trace metals such as iron and cobalt. Future climate change will likely alter ocean circulation and supply of trace metals to the surface ocean, and may impact Prochlorococcus populations, which can affect marine food webs. We only have information on iron and cobalt requirements for a few strains of Prochlorococcus. Therefore, we performed culturing experiments to understand the growth and decay of Prochlorococcus in a lab environment with changes in levels of iron and cobalt. Iron limitation on Atlantic Prochlorococcus did not have a significant impact on growth rates, while cobalt limitation experiments did significantly impact the growth of these phytoplankton when lowered. The growth rates resulting from these experiments can be used to model future changes in Prochlorococcus populations as the impacts of climate change become more prevalent.
Keywords: Prochlorococcus, trace metal, cobalt, iron, growth rate, limitatio
The Ocean’s Cobalt Cycle and its Correlations with other Metals
No full textThe metal cobalt is an essential nutrient for many important marine organisms, but its distribution across the oceans is not well known. When cobalt concentrations correlate with phosphate it is acting as a nutrient to marine organisms, but when it correlates with manganese it is normally an indication that there is a strong geological influence. Other metals such as manganese and phosphate are prominent elements in seawater compared to cobalt which is why they are used as proxies to cobalt (Zeng, 2019). Cobalt concentrations for over 100 samples from the TARA Oceans expedition were measured across the global ocean. The focus is on four regions: the North Pacific, South Pacific, West Pacific and the North Atlantic, which demonstrate how other elements can trace the cobalt cycle in the ocean. Cobalt exhibits similar behavior to phosphate in some regions and manganese in others. In the North-east Pacific region, Mexican and Central American coastal waters had a small correlation with manganese: cobalt concentration is higher when manganese is high. In the Southeast Pacific and South American coast, an increase in cobalt is detected when manganese is elevated. Cobalt concentrations from the Western Pacific region have not been reported previously. We observed increased cobalt concentrations off the coast of Australia, New Caledonia, and the coast of Papua New Guinea due to input from river systems from the land masses, as well as at the equator, to the upwelling of deep nutrient rich waters. Interestingly, Co and phosphate are correlated in the North Atlantic and Caribbean Sea. In this paper cobalt is traced by two metals from different sources that can paint a picture of the metal’s cycle and influence. By correlating cobalt with these two metals that are more easily measured elements, we can broaden our understanding of the cobalt cycle and its sources
Siderophore-based microbial adaptations to iron scarcity across the eastern Pacific Ocean
No full textNearly all iron dissolved in the ocean is complexed by strong organic ligands of unknown composition. The effect of ligand composition on microbial iron acquisition is poorly understood, but amendment experiments using model ligands show they can facilitate or impede iron uptake depending on their identity. Here we show that siderophores, organic compounds synthesized by microbes to facilitate iron uptake, are a dynamic component of the marine ligand pool in the eastern tropical Pacific Ocean. Siderophore concentrations in iron-deficient waters averaged 9 pM, up to fivefold higher than in iron-rich coastal and nutrient-depleted oligotrophic waters, and were dominated by amphibactins, amphiphilic siderophores with cell membrane affinity. Phylogenetic analysis of amphibactin biosynthetic genes suggests that the ability to produce amphibactins has transferred horizontally across multiple Gammaproteobacteria, potentially driven by pressures to compete for iron. In coastal and oligotrophic regions of the eastern Pacific Ocean, amphibactins were replaced with lower concentrations (1–2 pM) of hydrophilic ferrioxamine siderophores. Our results suggest that organic ligand composition changes across the surface ocean in response to environmental pressures. Hydrophilic siderophores are predominantly found across regions of the ocean where iron is not expected to be the limiting nutrient for the microbial community at large. However, in regions with intense competition for iron, some microbes optimize iron acquisition by producing siderophores that minimize diffusive losses to the environment. These siderophores affect iron bioavailability and thus may be an important component of the marine iron cycle.National Science Foundation (U.S.) (OCE-1356747)National Science Foundation (U.S.) (OCE-1233261)National Science Foundation (U.S.) (OCE-1237034)National Science Foundation (U.S.) (DBI-0424599)Gordon and Betty Moore Foundation (Grant GBMF3298)Gordon and Betty Moore Foundation (Grant GBMF3934)Simons Foundation (329108
Cobalt scavenging in the mesopelagic ocean and its influence on global mass balance: Synthesizing water column and sedimentary fluxes
No full textIn the ocean, dissolved cobalt is affected by both nutrient cycling and scavenging onto manganese oxides. The latter process concentrates Co in pelagic sediments, resulting in a small deep water inventory. While the flux of scavenged cobalt to sediments appears steady on timescales > 100,000 years, its residence time in the water column is short, approximately 130 years. Using results from recent GEOTRACES expeditions, we show net removal of dissolved Co from the deep ocean on the order of 0.043 pM year− 1, which corresponds to a turnover time of 980 years. Scavenging in deep ocean water masses is too slow to match cobalt accumulation rates in marine sediments, requiring most of the scavenging flux to derive from the mesopelagic ocean (< 1500 m depth) where nutrient cycling is active. Based on differences between the Co:P stoichiometry in particles sinking from the euphotic zone and dissolved Co:P remineralization ratios, we calculate areal scavenging rates in the North Atlantic and South Pacific basins on the order of 1.5 and 0.7 μmol m− 2 year− 1, respectively, which agree with long-term accumulation rates in Atlantic and Pacific sediments. In both basins, over 50% of the scavenged flux of cobalt occurs in the upper 500 m, resulting in decadal turnover times in the mesopelagic. An assessment of sources suggests that the marine cobalt cycle is approximately in balance, but that this inventory may be sensitive to long term trends in the intensity of oxygen minimum zones, which account for ~ 25% of the annual cobalt source to the modern oceans
Accompanying data for "Iron depletion in the deep chlorophyll maximum: mesoscale eddies as natural iron fertilization experiments"
No full textData accompanying manuscript, "Iron depletion in the deep chlorophyll maximum: mesoscale eddies as natural iron fertilization experiments", submitted to Global Biogeochemical Cycles. Contents include water column measurements from the 2017 MESO-SCOPE expedition, including underway CTD profiles, nutrients, trace metals, flow cytometry, primary productivity, Fe-ligand chromatograms, and results from Fe amendment experiments
Adaptive responses of marine diatoms to zinc scarcity and ecological implications
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kellogg, R., Moosburner, M., Cohen, N., Hawco, N., McIlvin, M., Moran, D., DiTullio, G., Subhas, A., Allen, A., & Saito, M. Adaptive responses of marine diatoms to zinc scarcity and ecological implications. Nature Communications, 13(1), (2022): 1995, https://doi.org/10.1038/s41467-022-29603-y.Scarce dissolved surface ocean concentrations of the essential algal micronutrient zinc suggest that Zn may influence the growth of phytoplankton such as diatoms, which are major contributors to marine primary productivity. However, the specific mechanisms by which diatoms acclimate to Zn deficiency are poorly understood. Using global proteomic analysis, we identified two proteins (ZCRP-A/B, Zn/Co Responsive Protein A/B) among four diatom species that became abundant under Zn/Co limitation. Characterization using reverse genetic techniques and homology data suggests putative Zn/Co chaperone and membrane-bound transport complex component roles for ZCRP-A (a COG0523 domain protein) and ZCRP-B, respectively. Metaproteomic detection of ZCRPs along a Pacific Ocean transect revealed increased abundances at the surface (<200 m) where dZn and dCo were scarcest, implying Zn nutritional stress in marine algae is more prevalent than previously recognized. These results demonstrate multiple adaptive responses to Zn scarcity in marine diatoms that are deployed in low Zn regions of the Pacific Ocean.This work was funded by the National Science Foundation (OCE-1736599 and OCE-1657766), NIH (R01GM135709), Gordon and Betty Moore Foundation (GBMF3782) to M.A.S., and Simons Foundation award 544236 to N.R.C. This work was further supported by the National Science Foundation (NSF-OCE-1756884 and NSF-MCB-1818390), United States Department of Energy (DE-SC0018344), and Gordon and Betty Moore Foundation grants GBMF3828 and GBMF5006 to A.E.A
Nutrient and particle data from offshore of Kilauea during the 2018 eruption and lava ocean entry
No full textSamples in this dataset were collected offshore of Kilauea volcano in 2018 during an active ocean entry of lava
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