Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Cohen, Natalie R.; Ellis, Kelsey A.; Lampe, Robert H.; McNair, Heather M.; Twining, Benjamin S.; Maldonado, María T.; Brzezinski, Mark A.; Kuzminov, Fedor I.; Thamatrakoln, Kimberlee; Till, Claire P.; Bruland, Kenneth W.; Sunda, William G.; Bargu, Sibel; Marchetti, Adrian

doi:10.3389/fmars.2017.00360

Cited by 58 publications

(84 citation statements)

References 95 publications

(112 reference statements)

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“…3A). Regardless of the situation (high iron to low iron or vice versa), diatoms were ultimately able to increase in relative abundance, aligning with their responsiveness to iron availability (32,33). In the transition from high to low iron, iron storage may play a role in allowing diatoms to continue to divide as growth rates in other taxa slow.…”

Section: Resultsmentioning

confidence: 96%

Different iron storage strategies among bloom-forming diatoms

Lampe

Mann

Cohen

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Diatoms are prominent eukaryotic phytoplankton despite being limited by the micronutrient iron in vast expanses of the ocean. As iron inputs are often sporadic, diatoms have evolved mechanisms such as the ability to store iron that enable them to bloom when iron is resupplied and then persist when low iron levels are reinstated. Two iron storage mechanisms have been previously described: the protein ferritin and vacuolar storage. To investigate the ecological role of these mechanisms among diatoms, iron addition and removal incubations were conducted using natural phytoplankton communities from varying iron environments. We show that among the predominant diatoms, Pseudo-nitzschia were favored by iron removal and displayed unique ferritin expression consistent with a long-term storage function. Meanwhile, Chaetoceros and Thalassiosira gene expression aligned with vacuolar storage mechanisms. Pseudo-nitzschia also showed exceptionally high iron storage under steady-state high and low iron conditions, as well as following iron resupply to iron-limited cells. We propose that bloom-forming diatoms use different iron storage mechanisms and that ferritin utilization may provide an advantage in areas of prolonged iron limitation with pulsed iron inputs. As iron distributions and availability change, this speculated ferritin-linked advantage may result in shifts in diatom community composition that can alter marine ecosystems and biogeochemical cycles.

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Section: Resultsmentioning

confidence: 96%

Different iron storage strategies among bloom-forming diatoms

Lampe

Mann

Cohen

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…that forms complexes with both Fe (log

K_{FeDA, {Fe}^{'}}^{cond}

= 8.7 ± 0.5) and Cu (log

K_{{CuDA, Cu}^{2 +}}^{cond}

= 9.0 ± 0.2) (Rue and Bruland ). While we did not measure DA in our experiment, DA concentrations approaching 4000 pg mL −1 (∼ 13 nM) were measured in incubation experiments conducted on the same cruise (Cohen et al ). Due to the relatively weak

K_{{CuDA, Cu}^{2 +}}^{cond}

and

K_{FeDA, {Fe}^{'}}^{cond}

of DA, concentrations 2–3 orders of magnitude higher would be required to see sufficient changes Cu ligands in the analytical window used in this study.…”

Section: Discussionmentioning

confidence: 94%

The biogeochemical cycling of iron, copper, nickel, cadmium, manganese, cobalt, lead, and scandium in a California Current experimental study

Mellett

Brown

Chappell

et al. 2017

Limnology & Oceanography

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A 3-day shipboard incubation experiment was conducted in the California Current System in July 2014 to investigate the cycling of iron (Fe), copper (Cu), nickel (Ni), cadmium (Cd), manganese (Mn), cobalt (Co), lead (Pb), and scandium (Sc) under a range of light and particle conditions. Filtered (< 0.2 lm) and unfiltered treatments were incubated under the following light conditions: Dark, light ("UV"), and light without the ultraviolet (UV) wavelengths ("noUV"). The experiment was sampled for carbon and Fe uptake rates, dissolved trace metal concentrations (Fe, Cu, Ni, Cd, Mn, Co, Pb, Sc), Fe and Cu speciation, size-fractionated concentrations of Cd and Fe, and diatom community composition from DNA sequencing. Exposure to UV light increased phytoplankton Fe uptake in the first 24 h of the incubation relative to the noUV treatment, suggesting that a fraction of the ambient ligand-bound Fe was photoreactive. Fe-binding organic ligand production was observed in the unfiltered light treatments in association with increasing chlorophyll a, and evidence for Cu-binding ligand production in these treatments was also observed. Biological uptake of Cd and Co was observed along with scavenging of dissolved Pb. Manganese appeared to be rapidly oxidized by Mnoxidizing bacteria with concomitant drawdown of dissolved Ni. Scandium displayed similar trends to Fe, reinforcing the limited observations of the physicochemical similarities between these two elements in seawater. Overall, this study highlights distinct impacts of photochemical processes, scavenging, and biological effects on marine trace metal cycling in an environment characterized by seasonal upwelling.The importance of iron (Fe) as a micronutrient has been established for nearly three decades (Martin and Fitzwater 1988). It is now recognized that Fe limits primary productivity in as much as 40% of the surface ocean and exerts significant influence on carbon cycling in the global ocean (Moore et al. 2004;Boyd et al. 2007;Tagliabue et al. 2017). Although Fe is a major constituent of the Earth's crust, its physicochemical properties result in low solubility in oxygenated seawater (Liu and Millero 2002). This scarcity in the water column is compounded by a high biological demand for Fe as a cofactor in enzymes that mediate critical biochemical reactions in phytoplankton such as nitrogen fixation and photosynthesis (Sunda 1989;Morel and Price 2003). This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. In addition to Fe, a suite of bioactive metals including copper (Cu), nickel (Ni), cobalt (Co), cadmium (Cd), and manganese (Mn), among others, have garnered attention for their biological utilization by phytoplankton and have been studied to determine the influence they exert on primary production in the oceans (Sunda 1989;Bruland et al. ...

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“…In our incubation experiments, members of the diatom genera Pseudo‐nitzschia and Thalassiosira were among the most dominant based on relative transcript abundance (Cohen et al ). Marchetti et al () developed a Pseudo‐nitzschia Iron‐Limitation Index (Ps‐n ILI), which is plotted for this incubation experiment in Fig.…”

Section: Resultsmentioning

confidence: 99%

The iron limitation mosaic in the California Current System: Factors governing Fe availability in the shelf/near‐shelf region

Till

Solomon

Cohen

et al. 2018

Limnology & Oceanography

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The California Current System is a productive eastern boundary region off the coasts of Washington, Oregon, and California. There is strong seasonality to the region, with high levels of rainfall and river input to the coastal ocean during the winter season, and coastal and Ekman upwelling during the spring and summer. Iron (Fe) input to the coastal ocean during the winter months can be stored in the continental shelf mud belts and then be delivered to the surface ocean by upwelling in the spring and summer. There have been a number of studies providing strong evidence of Fe‐limitation of diatom growth occurring in regions of the California Current System off of California, and the occurrence of Fe‐limitation has been linked with narrow continental shelf mud belt width and low river input. We provide evidence for potential Fe‐limitation of diatoms off the southern coast of Oregon in July 2014, just off the shelf break near Cape Blanco in a region with moderate shelf width and river input. Since eastern boundary regions account for a disproportionally large amount of global primary production, this observation of potential Fe‐limitation in an unexpected near‐shore region of the California Current System has implications for global models of primary productivity. In order to re‐evaluate the factors impacting Fe availability, we utilize satellite imagery to compare with historical datasets, and show that unexpected levels of Fe can often be explained by eddies, plumes of upwelled water moving offshore, or lack of recent upwelling.

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Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Cited by 58 publications

References 95 publications

Different iron storage strategies among bloom-forming diatoms

Different iron storage strategies among bloom-forming diatoms

The biogeochemical cycling of iron, copper, nickel, cadmium, manganese, cobalt, lead, and scandium in a California Current experimental study

The iron limitation mosaic in the California Current System: Factors governing Fe availability in the shelf/near‐shelf region

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