Regulation of primary productivity rate in the equatorial Pacific

Analysis of the Chl-specific rate of primary productivity (P{sup B}) as a function of subsurface nutrient concentration at >300 equatorial stations provides an answer to the question: What processes regulate primary productivity rate in the high-nutrient, low-chlorophyll waters of the equatorial Pacific In the western Pacific where there is a gradient in 60-m (NO{sub 3}) from 0 to {approximately}12 {mu}M, the productivity rate is a linear function of nutrient concentration; in the eastern Pacific where the gradient is from 12 to 28 {mu}M, the productivity rate is independent of nutrient concentration and limited to {approximately}36 mg C(mg Chl){sup {minus}1} d{sup {minus}1}, or a mean euphotic zone C-specific growth rate ({mu}) of 0.47 d{sup {minus}1}. However, rates downstream of the Galapagos Islands are not limited; they are 46.4 mg C(mg Chl){sup {minus}1} d{sup {minus}1} and {mu} = 0.57 d{sup {minus}1}, very close to the predicted nutrient-regulated rates in the absence of other limitation. This pattern of rate regulation can be accounted for by a combination of eolian Fe, subsurface nutrients, and sedimentary Fe derived from the Galapagos platform. In the low-nutrient western Pacific the eolian supply of Fe is adequate to allow productivity rate to be set by subsurface nutrient concentration.more » In the nutrient-rich easter equatorial region eolian Fe is inadequate to support productivity rates proportional to the higher nutrient concentrations, so in this region eolian Fe is rate limiting. Around the Galapagos Islands productivity rates reach levels consistent with nutrient concentrations; sedimentary Fe from the Galapagos platform seems adequate to support increased nutrient-regulated productivity rates in this region.« less

[1]  W. Thomas.  Phytoplankton Nutrient Enrichment Experiments off Baja California and in the Eastern Equatorial Pacific Ocean , 1969 .

[2]  F. Chavez,et al.  An estimate of new production in the equatorial Pacific , 1987 .

[3]  Francisco P. Chavez,et al.  Phytoplankton taxa in relation to primary production in the equatorial Pacific , 1990 .

[4]  John H. Martin.  glacial-interglacial Co2 change : the iron hypothesis , 1990 .

[5]  F. Chavez,et al.  Biological Consequences of El Ni�o , 1983, Science.

[6]  Rudolph W. Preisendorfer,et al.  Secchi disk science: Visual optics of natural waters1 , 1986 .

[7]  H. Bryden,et al.  Diagnostic Model of the Three-Dimensional Circulation in the Upper Equatorial Pacific Ocean , 1985 .

[8]  F. Chavez,et al.  Ocean variability in relation to living resources during the 1982–83 El Niño , 1986, Nature.

[9]  E. Steemann Nielsen,et al.  The Use of Radio-active Carbon (C14) for Measuring Organic Production in the Sea , 1952 .

[10]  Roger Lukas,et al.  The mixed layer of the western equatorial Pacific Ocean , 1991 .

[11]  R. Eppley.  AN INCUBATION METHOD FOR ESTIMATING THE CARBON CONTENT OF PHYTOPLANKTON IN NATURAL SAMPLES1 , 1968 .

[12]  W. S. Robinson.  Ecological correlations and the behavior of individuals. , 1950, International journal of epidemiology.

[13]  J. Ryther,et al.  Primary Organic Production in Relation to the Chemistry and Hydrography of the Western Indian OCEAN1 , 1966 .

[14]  John J. Walsh,et al.  Herbivory as a factor in patterns of nutrient utilization in the sea1 , 1976 .

[15]  A. Morel.  Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters) , 1988 .

[16]  K. Wyrtki.  An Estimate of Equatorial Upwelling in the Pacific , 1981 .

[17]  F. Azam,et al.  Toxic effects of latex and Tygon tubing on marine phytoplankton, zooplankton and bacteria , 1986 .

[18]  S. Fitzwater,et al.  Metal contamination and its effect on primary production measurements1 , 1982 .

[19]  W. Hurlin,et al.  Simulation of the Seasonal Cycle of the Tropical Pacific Ocean , 1987 .

[20]  R. Barber,et al.  Nutrients and Productivity During the 1982/83 El Niño , 1990 .

[21]  Curtiss O. Davis,et al.  Photosynthetic characteristics and estimated growth rates indicate grazing is the proximate control of primary production in the equatorial Pacific , 1992 .

[22]  F. Morel,et al.  Limitation of productivity by trace metals in the sea , 1991 .

[23]  G. Feldman.  Patterns Of Phytoplankton Production Around The Galapagos Islands , 1986 .

[24]  Rupert G. Miller.  Beyond ANOVA, basics of applied statistics , 1987 .

[25]  J. Ryther,et al.  Organic chelators: Factors affecting primary production in the cromwell current upwelling☆ , 1969 .

[26]  F. Wilkerson,et al.  Low specific nitrate uptake rate: A common feature of high‐nutrient, low‐chlorophyll marine ecosystems , 1991 .

[27]  J. Ryther,et al.  Nutrients limiting the production of phytoplankton in the Sargasso sea, with special reference to iron , 1961 .

[28]  J. Cullen.  Hypotheses to explain high-nutrient conditions in the open sea , 1991 .

[29]  F. Chavez.  Size Distribution of phytoplankton in the central and eastern tropical Pacific , 1989 .

[30]  W. Sunda,et al.  Low iron requirement for growth in oceanic phytoplankton , 1991, Nature.

[31]  Joseph M. Prospero,et al.  Transport of mineral aerosol from Asia Over the North Pacific Ocean , 1983 .

[32]  R. Gordon,et al.  Northeast Pacific iron distributions in relation to phytoplankton productivity , 1988 .

[33]  Francisco P. Chavez,et al.  Standing stocks of particulate carbon and nitrogen in the equatorial Pacific at 150°W , 1992 .