Controls on tropical Pacific Ocean productivity revealed through nutrient stress diagnostics

TY - JOUR

T1 - Controls on tropical Pacific Ocean productivity revealed through nutrient stress diagnostics

AU - Behrenfeld, Michael J.

AU - Worthington, Kirby

AU - Sherrell, Robert M.

AU - Chavez, Francisco P.

AU - Strutton, Peter

AU - McPhaden, Michael

AU - Shea, Donald M.

N1 - Funding Information: Acknowledgements We thank Z. Kolber, R. O’Malley, and the crew and officers of the NOAA ships Ka’imimoana and Ronald Brown. This research was funded by the National Science Foundation, the National Aeronautics and Space Administration, and the National Oceanic and Atmospheric Administration’s Tropical Atmosphere Ocean array programme.

PY - 2006/8/31

Y1 - 2006/8/31

N2 - In situ enrichment experiments have shown that the growth of bloom-forming diatoms in the major high-nitrate low-chlorophyll (HNLC) regions of the world's oceans is limited by the availability of iron. Yet even the largest of these manipulative experiments represents only a small fraction of an ocean basin, and the responses observed are strongly influenced by the proliferation of rare species rather than the growth of naturally dominant populations. Here we link unique fluorescence attributes of phytoplankton to specific physiological responses to nutrient stress, and use these relationships to evaluate the factors that constrain phytoplankton growth in the tropical Pacific Ocean on an unprecedented spatial scale. On the basis of fluorescence measurements taken over 12 years, we delineate three major ecophysiological regimes in this region. We find that iron has a key function in regulating phytoplankton growth in both HNLC and oligotrophic waters near the Equator and further south, whereas nitrogen and zooplankton grazing are the primary factors that regulate biomass production in the north. Application of our findings to the interpretation of satellite chlorophyll fields shows that productivity in the tropical Pacific basin may be 1.2-2.5 Pg C yr-1 lower than previous estimates have suggested, a difference that is comparable to the global change in ocean production that accompanied the largest El Niño to La Niña transition on record.

AB - In situ enrichment experiments have shown that the growth of bloom-forming diatoms in the major high-nitrate low-chlorophyll (HNLC) regions of the world's oceans is limited by the availability of iron. Yet even the largest of these manipulative experiments represents only a small fraction of an ocean basin, and the responses observed are strongly influenced by the proliferation of rare species rather than the growth of naturally dominant populations. Here we link unique fluorescence attributes of phytoplankton to specific physiological responses to nutrient stress, and use these relationships to evaluate the factors that constrain phytoplankton growth in the tropical Pacific Ocean on an unprecedented spatial scale. On the basis of fluorescence measurements taken over 12 years, we delineate three major ecophysiological regimes in this region. We find that iron has a key function in regulating phytoplankton growth in both HNLC and oligotrophic waters near the Equator and further south, whereas nitrogen and zooplankton grazing are the primary factors that regulate biomass production in the north. Application of our findings to the interpretation of satellite chlorophyll fields shows that productivity in the tropical Pacific basin may be 1.2-2.5 Pg C yr-1 lower than previous estimates have suggested, a difference that is comparable to the global change in ocean production that accompanied the largest El Niño to La Niña transition on record.

UR - https://www.scopus.com/pages/publications/33748319492

UR - https://www.scopus.com/pages/publications/33748319492#tab=citedBy

U2 - 10.1038/nature05083

DO - 10.1038/nature05083

M3 - Article

C2 - 16943835

SN - 0028-0836

VL - 442

SP - 1025

EP - 1028

JO - Nature

JF - Nature

IS - 7106

ER -