Published Work
Nick Hawco's Google Scholar Page
Research highlights
Tracing ocean anoxia with cobalt
Ocean deoxygenation is a major concern of ongoing climate change, but we don't know how the ocean's low oxygen regions - "Oxygen Deficient Zones" - have changed in the past.
Across the global ocean today, low oxygen waters have high cobalt. We found cobalt enrichments in marine sediments deposited on the seafloor during the last ice age, hinting that low oxygen waters were more prevalent in this cooler climate than they are today.
Projecting Antarctic Manganese Stress
Every molecule of oxygen that we breathe was borne on a cluster of manganese. The oxygen-evolving complex of photosystem II is a key reason why phytoplankton need manganese to survive.
In this paper, we use a state-of-the-art ecosystem model to see what happens when there's not enough manganese to go around. Widespread Mn stress in the Southern Ocean today could limit the ability of this ecosystem to respond to climate change.
Stress free iron recycling?
When iron is a limiting nutrient - like in the Southern Ocean or in the Equatorial Pacific - plankton communities work together to reduce, reuse and recycle the little iron that's present. In this paper, we measured rates of iron uptake and (re)cycling in the North Pacific gyre. Even though this is not an iron-limited ecosystem, iron was recycled none-the-less.
Iron recycling revealed by ocean eddy shake-ups
Life is challenging in the ocean's understory, where light, nitrogen and iron are all scarce.
We tracked down two opposing eddies that perturbed the supply of these resources. This natural experiment indicated a surprising ability for this ecosystem to conserve iron, allowing deep-dwelling phytoplankton to bloom.
Is cobalt a limiting nutrient?
Before oxygen filled the atmosphere, cobalt filled the oceans.
Today, cobalt is only one part per trillion of seawater but many organisms still remember the cobalt-rich oceans when they first evolved, and still require cobalt to grow.
We found that the most abundant type of phytoplankton on earth, the cyanobacterium Prochlorococcus, who has been able to shrink its cobalt requirement to just a few dozen atoms per cell, allowing it to thrive in the most remote parts of the oceans where cobalt is lowest.
Signatures of lava seawater interaction
The 2018 eruption of Kīlauea added almost a cubic kilometer of new lava to Hawaiʻi island, much of it pouring directly into the ocean.
By collecting and analyzing samples from seawater flowing away from the site of lava entry, we identified a unique elemental and isotopic signature associated with lava-seawater interaction.
Detecting anthropogenic iron in the North Pacific
Using isotope fingerprints of natural iron sources and industrially-derived iron, we confirmed model predictions that human activities are increasing the ocean's supply of iron.
Plankton need iron to conduct photosynthesis, but different types new different amounts. This new source may allow rare phytoplankton to become dominant.
Publications by year
2023
Hawco NJ, Foreman RK. Expansion of Ocean Anoxia During Glacial Periods Recorded in the Cobalt Flux to Pelagic Sediments. Geophysical Research Letters. 2023, 50(19). e2023GL105135. DOI: 10.1029/2023GL105135.
Park J, Durhman BP, Key RS, Groussman RD, Bartolek Z, Pinedo-González P, Hawco NJ, John SG, Carlson MCG, Lindell D, Juranek L, Ferrón S, Ribalet F, Armbrust EV, Ingalls AE, Bundy RM. Siderophore production and utilization by marine bacteria in the North Pacific Ocean. Limnology and Oceanography. 2023, 68(7): 1636-1653. DOI:10.1002/lno.12373.
Dugenne M, Gradoville MR, Church MJ, Wilson ST, Sheyn U, Harke MJ, Björkman KM, Hawco NJ, Hynes AM, Ribalet F, Karl DM, Delong EF, Dyhrman ST, Armbrust EV, John SG, Eppley JM, Harding K, Stewart B, Cabello AM, Turk-Kubo KA, Caffin M, White AE, Zehr JP. Nitrogen fixation in mesoscale eddies of the North Pacific Subtropical Gyre: patterns and mechanisms. Global Biogoechemical Cycles. 2023, 37(4), e2022GB007386. DOI: 10.1029/2022GB007386.
2022
Hawco NJ,* Tagliabue A,* and BS Twining. Manganese limitation of phytoplankton physiology and productivity in the Southern Ocean. Global Biogeochemical Cycles. *contributed equally. 2022, 36 (11), e2022GB007382. DOI:10.1029/2022GB007382.
Hawco NJ, Yang S-C, Pinedo-González P, Black EE, Kenyon J, Ferrón S, Bian X, John SG. Recycling of dissolved iron in the North Pacific Subtropical Gyre. Limnology and Oceanography. 2022, 67(11): 2448-2465. DOI:10.1002/lno.12212.
Barone B, Church MJ, Dugenne M, Hawco NJ, Jahn O, White AE, John SG, Follows MJ, DeLong EF, and Karl DK. Biogeochemical dynamics in adjacent mesoscale eddies of opposite polarity. Global Biogeochemical Cycles. 36, e2021GB007115. DOI: 10.1029/2021GB007115.
Kellogg RM, Moosburner MA, Cohen NR, Hawco NJ, McIlvin MR, Moram DM, DiTullio GR, Subhas AV, Allen AE, and Saito MA. Adaptive responses of marine diatoms to zinc scarcity and ecological implications. Nature communications. 13, 1, 1-13. DOI: 10.1038/s41467-022-29603-y.
2021
Hawco NJ, Barone B, Church MJ, Babcock-Adams L, Repeta DJ, Wear EK, Foreman RK, Björkman KM, Bent S, Van Mooy BAS, Sheyn U, Delong EF, Acker M, Kelly RL, Nelson A, Ranieri J, Clemente TM, Karl DM, and SG John. Iron depletion in the deep chlorophyll maximum: mesoscale eddies as natural iron fertilization experiments. Global Biogeochemical Cycles. 35, e2021GB007112, 2021. DOI: 10.1029/2021GB007112.
Hawco NJ, Fu F-X, Yang N, Hutchins DA, John SG. Independent iron and light limitation in a low-light adapted Prochlorococcus from the deep chlorophyll maximum. ISME J. 15, 359-362, 2021.
Foreman RK, Björkman KM, Funkey CP, Hawco NJ, Wilson ST, Rohrer T, White AE, John SG, Karl DM. Phosphate scavenging during lava-seawater interaction offshore of Kīlauea volcano, Hawaii. Geochemistry, Geophysics, Geosystems. In press.
Yang N, Merkel CA, Lin Y-A, Levine NM, Hawco NJ, Jang H-B, Qu P-P, DeMers MA, Webb EA, Fu F-X, Hutchins DA. Warming iron-limited oceans enhance nitrogen fixation and drive biogeographic specialization of the globally important cyanobacterium Crocosphaera. Frontiers in Marine Science. In press.
Kelly RL, Bian X, Feakins SJ, Fornace KL, Gunderson T, Hawco NJ, Niggemann J, Paulson SE, Pinedo-Gonzalez P, West AJ, Yang SC, and John SG. Delivery of Metals and Dissolved Black Carbon to the Southern California Coastal Ocean via Aerosols and Floodwaters Following the 2017 Thomas Fire. Journal of Geophysical Research: Biogeosciences, 126, e2020JG006117.
Cohen NR, McIlvin MR, Moran DM, Held NA, Saunders JK, Hawco NJ, Brosnahan M, DiTullio GR, Lamborg C, McCrow JP, Dupont CL, Allen AE, and Saito MA. Dinoflagellates alter their carbon and nutrient metabolic strategies across environmental gradients in the central Pacific Ocean. Nature Microbiology, 6, 173-186, 2021.
2020
Hawco NJ, McIlvin MR, Bundy RM, Tagliabue A, Goepfert TJ, Moran D, Valentin-Alvarado L, DiTullio G, Saito MA. Minimal cobalt metabolism in the marine cyanobacterium Prochlorococcus. Proceedings of the National Academy of Sciences, 117 (27), 15740-15747, 2020.
Hawco NJ, Yang S-C, Foreman RK, Funkey CP, Dugenne M, White AE, Wilson ST, Kelly RL, Bian X, Huang KF, Karl DM, John SG. Metal isotope signatures from lava-seawater interaction during the 2018 eruption of Kīlauea. Geochimica et Cosmochimica Acta, 282, 340-356, 2020.
Pinedo-Gonzalez P, Hawco NJ, Bundy RM, Armbrust EV, Follows MJ, Cael BB, White AE, Ferrón S, Karl DM, and John SG. Anthropogenic Asian aerosols provide Fe to the North Pacific. Proceedings of the National Academy of Sciences, 117 (45), 27862-27868, 2020.
Yang S-C, Hawco NJ, Pinedo-Gonzalez P, Bian, X, Huang KF, Zhang R, and John SG. A new purification method for Ni and Cu stable isotopes in seawater shows widespread Ni isotope fractionation by phytoplankton. Chemical Geology. 547, 11962, 2020.
Bundy RM, Tagliabue A, Hawco NJ, Morton PL, Twining BS, Hatta M, Noble AE, Cape MR, John SG, Cullen JT, and Saito MA. Elevated cobalt sources in the Arctic Ocean. Biogeosciences, 17 (19), 4745-4767, 2020.
2019
Wilson ST*, Hawco NJ*, Armbrust EV, Barone B, Björkman KM, Boysen AK, Burgos M, Burrell TJ, Casey JR, DeLong EF, Dugenne M, Dutkiewicz S, Dyhrman ST, Ferrón S, Follows MJ, Foreman RK, Funkey CP, Harke MJ, Henke BA, Hill CN, Hynes AM, Ingalls AE, Jahn O, Kelly RL, Knapp AN, Letelier RM, Ribalet F, Shimabukuro EM, Tabata RKS, Turk-Kubo KA, White AE, Zehr JP, John SG, and Karl DM. Kīlauea Lava Fuels Phytoplankton Bloom in the North Pacific Ocean. Science, 365, 1040–44, 2019. *co-lead author.
2018
Hawco NJ and Saito MA. Competitive Inhibition of cobalt uptake by zinc and manganese in a Pacific Prochlorococcus strain: insights into metal homeostasis in a streamlined oligotrophic cyanobacterium. Limnology and Oceanography, 63 (5), 2229-2249, 2018.
Hawco NJ, Lam PJ, Lee JM, Ohnemus DC, Noble AE, Wyatt NJ, Lohan MC, and Saito MA. Cobalt scavenging in the mesopelagic ocean and its influence on global mass balance: Synthesizing water column and sedimentary fluxes. Marine Chemistry, 201 (20), 151-166, 2018.
Tagliabue A, Hawco NJ, Bundy RM, Landing WM, Morton PL and MA Saito. The role of external inputs and internal cycling in shaping the global ocean cobalt distribution: Insights from the first cobalt biogeochemical model. Global Biogeochemical Cycles, 32, 594-616, 2018.
Sanial V, Kipp LE, Henderson PB, van Beek P, Reyss JL, Hammond DE, Hawco NJ, Saito MA, Resing JA, Sedwick P, Moore WS, and Charette MA. Radium-228 as a tracer of dissolved trace element inputs from the Peruvian continental margin. Marine Chemistry, 201 (20), 20-34, 2018.
Schlitzer R, Anderson RF, Dodasc EM, Lohan MC, Geiberta W, Tagliabue A, Bowie A, Jeandel C, Maldonado MT, Landing WM, Cockwell, Abadie C, Abouchami W, Achterberg EP, Agather A, Aguilar-Islas A, van Aken HM, … Hatta M, Hawco NJ, Hayes CT, … Zunino P, Zurbrick C (100+ authors omitted). The GEOTRACES Intermediate Data Product 2017. Chemical Geology, 493 210-223, 2018.
2017
Saito MA, Noble AE, Hawco NJ, Twining BS, Ohnemus DC, John SJ, Lam PJ, Conway TM, Johnson R, Moran DA, McIlvin MR. The acceleration of dissolved cobalt’s ecological stoichiometry due to biological uptake remineralization and scavenging in the Atlantic Ocean. Biogeosciences, 14 (20), 4637-4662, 2017.
Noble AE, Ohnemus DC, Hawco NJ, Lam PJ, Saito MA. Coastal Sources Sinks and Strong Organic Complexation of Dissolved Cobalt within the US North Atlantic GEOTRACES Transect GA03. Biogeosciences 14 (11), 2715-2739, 2017.
2016
Hawco NJ, Ohnemus DC, Resing JR, Twining BS, and Saito MA. A cobalt plume in the oxygen minimum zone of the Eastern South Pacific. Biogeosciences, 13 (20), 5697, 2016.
Boiteau RM, Mende DR, Hawco NJ, McIlvin MR, Sedwick PN, Saito MA, Delong EF, Repeta DJ. Siderophore-based microbial adaptations to iron scarcity across the eastern Pacific Ocean. Proceedings of the National Academy of Sciences, 113 (50), 14237-14242, 2016.
Boiteau RM, Till CP, Raucho A, Bundy RM, Hawco NJ, McKenna AM, Barbeau KA, Bruland KW, Saito MA, Repeta DJ. Structural characterization of natural nickel and copper binding ligands along the US GEOTRACES Eastern Tropical Pacific Zonal Transect. Frontiers in Marine Science 3, 243, 2016.