Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Dissolved organic phosphorus concentrations in the surface ocean controlled by both phosphate and iron stress


Dissolved organic phosphorus (DOP) has a dual role in the surface ocean as both a product of primary production and as an organic nutrient that fuels primary production and nitrogen fixation, especially in oligotrophic gyres. Although poorly constrained, the geographic distribution and environmental controls of surface ocean DOP concentrations influence the distributions and rates of primary production and nitrogen fixation in the global ocean. Here we pair DOP concentration measurements with a metric of phosphate stress, satellite-based chlorophyll a concentrations and a satellite-based iron stress proxy to explore their relationship with upper 50 m DOP stocks. Our results suggest that phosphate and iron stress work together to control surface ocean DOP concentrations at basin scales. Specifically, upper 50 m DOP stocks decrease with increasing phosphate stress, while alleviated iron stress leads to either surface DOP accumulation or loss depending on phosphate availability. Our work extends the relationship between DOP concentrations and phosphate availability to the global ocean, suggests a linkage between marine phosphorus cycling and iron availability and establishes a predictive framework for DOP distributions and their use as an organic nutrient source that supports global ocean fertility.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Distribution of DOP concentrations and the relationship between the upper 50 m DOP stocks and P* over the global ocean.
Fig. 2: Relationships between upper 50 m DOP stocks, surface chlorophyll a concentration and NPQ-corrected φsat.
Fig. 3: Conceptual model of factors influencing surface ocean DOP distributions with representative ocean regions.

Data availability

Original DOP data used in this study can be found and freely accessed in the DOPv2021 database archived on the BCO DMO website ( or in the Woods Hole Open Access Server ( The Level-3 satellite product can be downloaded from the NASA OceanColor website (

Code availability

Code and data used to reproduce Figs. 1 and 2 are archived at


  1. Björkman, K. M. & Karl, D. M. Bioavailability of dissolved organic phosphorus in the euphotic zone at Station ALOHA, North Pacific Subtropical Gyre. Limnol. Oceanogr. 48, 1049–1057 (2003).

    Article  Google Scholar 

  2. Mather, R. L. et al. Phosphorus cycling in the North and South Atlantic Ocean subtropical gyres. Nat. Geosci. 1, 439–443 (2008).

    Article  Google Scholar 

  3. Lomas, M. W. et al. Sargasso Sea phosphorus biogeochemistry: an important role for dissolved organic phosphorus (DOP). Biogeosciences 7, 695–710 (2010).

    Article  Google Scholar 

  4. Dyhrman, S. T. et al. Phosphonate utilization by the globally important marine diazotroph Trichodesmium. Nature 439, 68–71 (2006).

    Article  Google Scholar 

  5. Dyhrman, S. T. & Ruttenberg, K. C. Presence and regulation of alkaline phosphatase activity in eukaryotic phytoplankton from the coastal ocean: implications for dissolved organic phosphorus remineralization. Limnol. Oceanogr. 51, 1381–1390 (2006).

    Article  Google Scholar 

  6. Orchard, E. D., Ammerman, J. W., Lomas, M. W. & Dyhrman, S. T. Dissolved inorganic and organic phosphorus uptake in Trichodesmium and the microbial community: the importance of phosphorus ester in the Sargasso Sea. Limnol. Oceanogr. 55, 1390–1399 (2010).

    Article  Google Scholar 

  7. Sato, M., Sakuraba, R. & Hashihama, F. Phosphate monoesterase and diesterase activities in the North and South Pacific Ocean. Biogeosciences 10, 7677–7688 (2013).

    Article  Google Scholar 

  8. Reynolds, S., Mahaffey, C., Roussenov, V. & Williams, R. G. Evidence for production and lateral transport of dissolved organic phosphorus in the eastern subtropical North Atlantic. Global Biogeochem. Cycles 28, 805–824 (2014).

    Article  Google Scholar 

  9. Diaz, J. M. et al. Dissolved organic phosphorus utilization by phytoplankton reveals preferential degradation of polyphosphates over phosphomonoesters. Front. Mar. Sci. (2018).

  10. Duhamel, S. et al. Phosphorus as an integral component of global marine biogeochemistry. Nat. Geosci. 14, 359–368 (2021).

    Article  Google Scholar 

  11. Letscher, R. T. & Moore, J. K. Preferential remineralization of dissolved organic phosphorus and non-Redfield DOM dynamics in the global ocean: impacts on marine productivity, nitrogen fixation, and carbon export. Global Biogeochem. Cycles 29, 325–340 (2015).

    Article  Google Scholar 

  12. Carlson, C. A. & Hansell, D. A. in Biogeochemistry of Marine Dissolved Organic Matter 2nd edn (eds. Hansell, D. A. & Carlson, C. A.) 65–126, Ch. 3 DOM Sources, Sinks, Reactivity, and Budgets (Academic Press, 2015);

  13. Browning, T. J. et al. Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic. Nat. Commun. 8, 15465 (2017).

    Article  Google Scholar 

  14. Mahaffey, C., Reynolds, S., Davis, C. E. & Lohan, M. C. Alkaline phosphatase activity in the subtropical ocean: insights from nutrient, dust and trace metal addition experiments. Front. Mar. Sci. (2014)

  15. Deutsch, C., Sarmiento, J. L., Sigman, D. M., Gruber, N. & Dunne, J. P. Spatial coupling of nitrogen inputs and losses in the ocean. Nature 445, 163–167 (2007).

    Article  Google Scholar 

  16. Behrenfeld, M. J. et al. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton. Biogeosciences 6, 779–794 (2009).

    Article  Google Scholar 

  17. Church, M. J., Ducklow, H. W. & Karl, D. M. Multiyear increases in dissolved organic matter inventories at Station ALOHA in the North Pacific Subtropical Gyre. Limnol. Oceanogr. 47, 1–10 (2002).

    Article  Google Scholar 

  18. Quigg, A. et al. The evolutionary inheritance of elemental stoichiometry in marine phytoplankton. Nature 425, 291–294 (2003).

    Article  Google Scholar 

  19. Bronk, D. A. & Ward, B. B. Gross and net nitrogen uptake and DON release in the euphotic zone of Monterey Bay, California. Limnol. Oceanogr. 44, 573–585 (1999).

    Article  Google Scholar 

  20. Hansell, D. A. & Carlson, C. A. Biogeochemistry of total organic carbon and nitrogen in the Sargasso Sea: control by convective overturn. Deep Sea Res. 2 Top. Stud. Oceanogr. 48, 1649–1667 (2001).

    Article  Google Scholar 

  21. Letscher, R. T., Hansell, D. A., Carlson, C. A., Lumpkin, R. & Knapp, A. N. Dissolved organic nitrogen in the global surface ocean: distribution and fate. Global Biogeochem. Cycles 27, 141–153 (2013).

    Article  Google Scholar 

  22. Knapp, A. N., Casciotti, K. L. & Prokopenko, M. G. Dissolved organic nitrogen production and consumption in eastern tropical South Pacific surface waters. Global Biogeochem. Cycles 32, 769–783 (2018).

    Article  Google Scholar 

  23. Raimbault, P., Garcia, N. & Cerutti, F. Distribution of inorganic and organic nutrients in the South Pacific Ocean – evidence for long-term accumulation of organic matter in nitrogen-depleted waters. Biogeosciences 5, 281–298 (2008).

    Article  Google Scholar 

  24. Garcia, H. E. et al. World Ocean Atlas 2013. Volume 4: Dissolved Inorganic Nutrients (Phosphate, Nitrate, Silicate) (eds Levitus, S., Mishonov, A.) NOAA atlas NESDIS series No. 76 (NOAA, 2013).

  25. DeVries, T., Deutsch, C., Primeau, F., Chang, B. & Devol, A. Global rates of water-column denitrification derived from nitrogen gas measurements. Nat. Geosci. 5, 547–550 (2012).

    Article  Google Scholar 

  26. Sohm, J. A., Mahaffey, C. & Capone, D. G. Assessment of relative phosphorus limitation of Trichodesmium spp. in the North Pacific, North Atlantic, and the north coast of Australia. Limnol. Oceanogr. 53, 2495–2502 (2008).

    Article  Google Scholar 

  27. Browning, T. J., Bouman, H. A. & Moore, C. M. Satellite-detected fluorescence: decoupling nonphotochemical quenching from iron stress signals in the South Atlantic and Southern Ocean. Global Biogeochem. Cycles 28, 510–524 (2014).

    Article  Google Scholar 

  28. Westberry, T. K. et al. Annual cycles of phytoplankton biomass in the subarctic Atlantic and Pacific Ocean. Global Biogeochem. Cycles 30, 175–190 (2016).

    Article  Google Scholar 

  29. Hopwood, M. J. et al. Non-linear response of summertime marine productivity to increased meltwater discharge around Greenland. Nat. Commun. 9, 3256 (2018).

    Article  Google Scholar 

  30. Larkin, A. A. et al. Subtle biogeochemical regimes in the Indian Ocean revealed by spatial and diel frequency of Prochlorococcus haplotypes. Limnol. Oceanogr. 65, S220–S232 (2020).

    Article  Google Scholar 

  31. Hashihama, F. et al. Biogeochemical controls of particulate phosphorus distribution across the oligotrophic subtropical Pacific Ocean. Global Biogeochem. Cycles 34, e2020GB006669 (2020).

    Article  Google Scholar 

  32. Mahowald, N. M. et al. Atmospheric global dust cycle and iron inputs to the ocean. Global Biogeochem. Cycles (2005)

  33. Guieu, C. et al. Iron from a submarine source impacts the productive layer of the Western Tropical South Pacific (WTSP). Sci. Rep. 8, 9075 (2018).

    Article  Google Scholar 

  34. Carpenter, E. J., Subramaniam, A. & Capone, D. G. Biomass and primary productivity of the cyanobacterium Trichodesmium spp. in the tropical N Atlantic ocean. Deep Sea Res. 1 Oceanogr. Res. Pap. 51, 173–203 (2004).

    Article  Google Scholar 

  35. Capone, D. G. et al. Nitrogen fixation by Trichodesmium spp.: an important source of new nitrogen to the tropical and subtropical North Atlantic Ocean. Global Biogeochem. Cycles (2005)

  36. Knapp, A. N. et al. Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets. Biogeosciences 15, 2619–2628 (2018).

    Article  Google Scholar 

  37. Caffin, M. et al. N2 fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise). Biogeosciences 15, 2565–2585 (2018).

    Article  Google Scholar 

  38. Van Mooy, B. A. S. et al. Quorum sensing control of phosphorus acquisition in Trichodesmium consortia. ISME J. 6, 422–429 (2012).

    Article  Google Scholar 

  39. Behrenfeld, M. J. et al. Controls on tropical Pacific Ocean productivity revealed through nutrient stress diagnostics. Nature 442, 1025–1028 (2006).

    Article  Google Scholar 

  40. Schrader, P. S., Milligan, A. J. & Behrenfeld, M. J. Surplus photosynthetic antennae complexes underlie diagnostics of iron limitation in a cyanobacterium. PLoS ONE 6, e18753 (2011).

    Article  Google Scholar 

  41. Chappell, P. D., Moffett, J. W., Hynes, A. M. & Webb, E. A. Molecular evidence of iron limitation and availability in the global diazotroph Trichodesmium. ISME J. 6, 1728–1739 (2012).

    Article  Google Scholar 

  42. Moreno, C. M., Gong, W., Cohen, N. R., DeLong, K. & Marchetti, A. Interactive effects of iron and light limitation on the molecular physiology of the Southern Ocean diatom Fragilariopsis kerguelensis. Limnol. Oceanogr. 65, 1511–1531 (2020).

    Article  Google Scholar 

  43. Hu, C. et al. Dynamic range and sensitivity requirements of satellite ocean color sensors: learning from the past. Appl. Opt. 51, 6045–6062 (2012).

    Article  Google Scholar 

  44. Huot, Y., Franz, B. A. & Fradette, M. Estimating variability in the quantum yield of Sun-induced chlorophyll fluorescence: a global analysis of oceanic waters. Remote Sens. Environ. 132, 238–253 (2013).

    Article  Google Scholar 

  45. Lin, H. et al. The fate of photons absorbed by phytoplankton in the global ocean. Science 351, 264–267 (2016).

    Article  Google Scholar 

  46. Foreman, R. K., Björkman, K. M., Carlson, C. A., Opalk, K. & Karl, D. M. Improved ultraviolet photo-oxidation system yields estimates for deep-sea dissolved organic nitrogen and phosphorus. Limnol. Oceanogr. Methods 17, 277–291 (2019).

    Article  Google Scholar 

  47. Ustick, L. J. et al. Metagenomic analysis reveals global-scale patterns of ocean nutrient limitation. Science 372, 287–291 (2021).

    Article  Google Scholar 

  48. Weber, T. & Deutsch, C. Local versus basin-scale limitation of marine nitrogen fixation. Proc. Natl Acad. Sci. USA 111, 8741–8746 (2014).

    Article  Google Scholar 

  49. Wang, W.-L., Moore, J. K., Martiny, A. C. & Primeau, F. W. Convergent estimates of marine nitrogen fixation. Nature 566, 205–211 (2019).

    Article  Google Scholar 

  50. Repeta, D. J. et al. Marine methane paradox explained by bacterial degradation of dissolved organic matter. Nat. Geosci. 9, 884–887 (2016).

    Article  Google Scholar 

  51. Schlitzer, R. Ocean Data View (2021);

  52. Monaghan, E. J. & Ruttenberg, K. C. Dissolved organic phosphorus in the coastal ocean: reassessment of available methods and seasonal phosphorus profiles from the Eel River Shelf. Limnol. Oceanogr. 44, 1702–1714 (1999).

    Article  Google Scholar 

  53. Armstrong, Fa. J., Williams, P. M. & Strickland, J. D. H. Photo-oxidation of organic matter in sea water by ultra-violet radiation, analytical and other applications. Nature 211, 481–483 (1966).

    Article  Google Scholar 

  54. Pujo-Pay, M. & Raimbault, P. Improvement of the wet-oxidation procedure for simultaneous determination of particulate organic nitrogen and phosphorus collected on filters. Mar. Ecol. Prog. Ser. 105, 203–207 (1994).

    Article  Google Scholar 

  55. NASA Goddard Space Flight Center, Ocean Ecology Laboratory & Ocean Biology Processing Group Moderate-Resolution Imaging Spectroradiometer (MODIS) Aqua Chlorophyll a 9km Data (NASA OB.DAAC, accessed 20 Jan 2021);

  56. Vapnik, V. The Nature of Statistical Learning Theory 2nd edn (Springer, 2013)

  57. Breiman, L. Random forests. Mach. Learn. 45, 5–32 (2001).

    Article  Google Scholar 

  58. Rasmussen, C. E. & Williams, C. K. I. Gaussian Processes for Machine Learning (MIT Press, 2005).

  59. Trujillo-Ortiz, A. & Hernandez-Walls, R. gmregress: Geometric Mean Regression (Reduced Major Axis Regression) (MathWorks, 2022);

  60. Pawlowicz, R. M_Map: A Mapping Package for MATLAB v.1.4m (UBC EOAS, 2020);

  61. Knapp, A. N., Liang, Z. & Letscher, R. T. DOP Concentration Observations From the Global Ocean Between 1990 and 2021 (DOP N2 Fixation and Export Production Project) Version 2 (Biological and Chemical Oceanography Data Management Office, 2022);

Download references


The work was supported by NSF OCE-1829797 (A.N.K.) and NSF OCE-1829916 (R.T.L.). We also gratefully acknowledge T.K. Westberry who provided useful feedback on NPQ-corrected φsat.

Author information

Authors and Affiliations



Z.L. performed the analysis. Z.L. and A.N.K. designed the study. Z.L., A.N.K. and R.T.L. wrote the paper. A.N.K. and R.T.L. led the project.

Corresponding author

Correspondence to Zhou Liang.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Geoscience thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editors: James Super and Kyle Frischkorn, in collaboration with the Nature Geoscience team.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Table 1 R2 of observed DOP concentration vs. predicted surface ocean DOP concentration based on different machine learning models (SVM, boosted tree and Gaussian process regression) with different predictors

Extended Data Fig. 1 Boxplots of mean DOP concentrations in the surface ocean (0–50 m) in different ocean basins.

Asterisks denote confidence levels when testing for unique mean concentrations between basins with ****: P< 0.0001, ***: P< 0.001, *: P< 0.05, using Dunn test (pairwise Kruskal–Wallis test) with Bonferroni correction. Black dots above the Eastern North Pacific and Gulf of Mexico are outliers. Center line is median and box limits are upper and lower quartiles. Whiskers show 1.5x interquartile range.

Extended Data Fig. 2 Correlation between observed upper 50 m DOP stock (mmol m2) and mean upper 50 m P* (µM) computed from the same samples.

Black solid line is the best fit line using a Type II linear regression model and dashed blue lines are the 95% confidence level. Three stations from the BIOSOPE cruise had only phosphate but no nitrate concentration measurements and they are not included in this figure.

Extended Data Fig. 3 Correlation between observed upper 50 m DOP stock (mmol m−2) and climatological mean P* (µM) between 100 m and 250 m computed from the World Ocean Atlas 2013 (ref. 24).

Black solid line is the best fit line using a Type II linear regression model and dashed blue lines are the 95% confidence level. There are 12 stations containing DOP data with a bottom depth <100 m which have not been included in this figure.

Extended Data Fig. 4 Annual mean surface geostrophic currents (0.25° × 0.25°) and identified surface current convergence zones (SCZ).

Annual mean geostrophic currents (0.25° × 0.25°) are obtained from the Copernicus Marine Environmental Monitoring Service ( Three surface current convergence zones (SCZ) are identified in the North Pacific, South Pacific and South Atlantic by red circle.

Extended Data Fig. 5

Predicted surface ocean DOP concentrations (µM) based on the linear relationship between DOP concentrations and P* (Fig. 1; see main text).

Supplementary information

Supplementary Information

Supplementary Figs. 1 and 2.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Liang, Z., Letscher, R.T. & Knapp, A.N. Dissolved organic phosphorus concentrations in the surface ocean controlled by both phosphate and iron stress. Nat. Geosci. 15, 651–657 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing