Pacific, equatorial

Deep-sea manganese nodules represent a significant potential mineral resource. Whereas the principal constituent of these deposits is manganese, the primary interest has come from the associated metals that the nodules can also contain (see Ocean rawmaterials). For example, metals can range from 0.01—2.0% nickel, 0.01—2.0% copper, and 0.01—2.25% cobalt (12). Recovery is considered an economic potential in the northwestern equatorial Pacific, and to a lesser degree in the southern and western Pacific and Indian Oceans (13—18). 

Fig. 10-7 Schematic of normal and El Nino conditions in the equatorial Pacific. (Figure kindly provided by Dr Michael McPhaden of NOAA.)...

Silicic acid (H4Si04) is a necessary nutrient for diatoms, who build their shells from opal (Si02 H20). Whether silicic acid becomes limiting for diatoms in seawater depends on the availability of Si relative to N and P. Estimates of diatom uptake of Si relative to P range from 16 1 to 23 1. Dugdale and Wilkerson (1998) and Dunne et al. (1999) have shown that much of the variability in new production in the equatorial Pacific may be tied to variability in diatom production. Diatom control is most important at times of very high nutrient concentrations and during non-steady-state times, perhaps because more iron is available at those times. 

Over 20% of the world s open ocean surface waters are replete in light and major nutrients (nitrate, phosphate, and silicate), yet chlorophyll and productivity values remain low. These so-called "high-nitrate low-chlorophyll" or HNLC regimes (Chisholm and Morel, 1991) include the sub-arctic North Pacific (Martin and Fitzwater, 1988 Martin et al, 1989 Miller et al, 1991), the equatorial Pacific (Murray et al, 1994 Fitzwater et al, 1996) and the southern Ocean (Martin et al.,... 

The equatorial undercurrent appears to be an additional source of the equatorial Pacific. 

The results of two successful iron-fertilization experiments in the eastern equatorial Pacific have clearly shown that phytoplankton growth rate is limited by iron at that location (Martin et al., 1994 Coale et al., 1996). The species composition and size distributions of the ecosystem are influenced by iron availability (Landry et al., 1997). In particular, large diatoms do not grow at optimum rates in the absence of sufficient iron. Loukos et al. (1997) used a simple... 

Archer, D., Peltzer, E. T. and Kirchman, D. (1997). A timescale for dissolved organic carbon production in equatorial Pacific surface waters. Glob. Biogeochem. Cycles 11,435-452. 

Coale, K. H., Johnson, K. S., Fitzwater, S. E. et al. (1996). A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean. Nature 383, 495-501. 

Cullen, J. J., Lewis, M. R., Davis, C. O. and Barber, R. T. (1992). Photosynthetic characteristics and estimated growth rates indicate grazing is the proximate control of primary production in the equatorial Pacific. /. Geophys. Res. 97,639-654. 

Dugdale, R. C. and WUkerson, F. P. (1998). Silicate regulation of new production in the equatorial Pacific upwelling. Nature 391,270-273. 

Durme, J. P., Murray, J. W., Aufdenkampe, A., Blain, S. and Rodier, M. (1999). Silicon-nitrogen coupling in the equatorial Pacific upwelling zone. Glob. Biogeochem. Cycles 131,715-726. 

Feely, R. A., Wanninkhof, R., Goyet, C. et al. (1997). Variability of CO2 distributions and sea-air fluxes in the central and eastern equatorial Pacific during the 1991-94 El Nino. Deep-Sea Res. II44,1851-1868. 

Hansell, D. A., Bates, N. R. and Carlson, C. A. (1997). Predominance of vertical loss of carbon from surface waters of the equatorial Pacific Ocean. Nature 386,59-61. 

Landry, M. R., Barber, R. T., Bidigare, R. R. et al. (1997). Iron and grazing constraints on primary production in the central equatorial Pacific and EqPac synthesis. Limnol. Oceanogr. 42,405-418. 

Loukos, H., Frost, B., Harrison, D. E. and Murray, J. W. (1997). An ecosystem model with iron limitation of primary production in the equatorial Pacific at 140 =W. Deep-Sea Res. II44,2221-2249. 

Martin, J. H. et al. (1994). Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean. Nature 371,123-129. 

Murray, J. W., Young, J., Newton, J. et al. (1996). Export flux of particulate organic carbon from the central equatorial Pacific determined using a combined drifting trap- Th approach. Deep-Sea Res. II 45,1095-1132. 

Peltzer, E. T. and Hayward, N. A. (1996). Spatial and temporal variability of total organic carbon along 140 W in the equatorial Pacific Ocean in 1992. Deep-Sea Res. II43, 1155-1180. 

Yamazaki, T, Katsura, I. and Marumo, K. (1991) Origin of stable remanent magnetization of siliceous sediments in the central equatorial Pacific. Earth Planet. Sci. Lett., 105, 81—93. 

Bidigare RR, Hanson KL, Buesseler KO, Wakeham SG, Freeman KH, Pancost RD, Millero FJ, Steinberg P, Popp BN, Latasa M, Landry MR, Laws EA (1999) Iron-stimulated changes in C-13 fractionation and export by equatorial Pacific phytoplankton Toward a paleogrowth rate proxy. Paleoceanography 15 (5) 589-595... 

Duime JP, Murray JW, Rodier M, Hansell DA (2000) Export flux in the western and central equatorial Pacific zone and temporal variability. Deep-Sea Res 147 901-936 Eppley RW, Peterson BJ (1979) Particulate organic matter flux and planktonic new production in the deep ocean. Nature 282 670-680... 

Nozaki Y, Zhang J, Takeda A (1997) °Pb and °Po in the equatorial Pacific and Bering Sea the effects of biological productivity and boundary scavenging. Deep-Sea Res II 44 2203-2220 Nozaki Y, Dobashi F, Kato Y, Yamamoto Y (1998) Distribution of Ra isotopes and the °Pb and °Po balance in surface waters of the mid Northern Hemisphere. Deep-Sea Res. 145 1263-1284 Pates JM, Cook GT, MacKenzie AB, Anderson R, Bury SJ (1996) Determination of Th-234 in marine samples by liquid scintillation spectrometry. Anal Chem 68 3783-3788... 

Pope RH, DeMaster DJ, Smith CR, Seltman Jr H (1996) Rapid bioturbation in equatorial Pacific sediments evidence from excess measurements. Deep-Sea Res 1143 1339-1364. 

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