Published Work

Nick Hawco's CV and Google Scholar

Research highlights

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.

Read the full paper here.

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.

Read the full paper here.

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.

Read the full paper here.

Publications by year


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.


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.


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.


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.


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.


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.