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FROM VOLUME 4, NUMBER 10, OCTOBER 1991
MARINE CARBON AND FERTILIZATION
"The Photolysis of Colloidal Iron in the Oceans," M.L. Wells
(Darling Marine Ctr., Univ. Maine, Walpole ME 04573), L.M. Mayer et al., Nature,
353(6341), 248-250, Sep. 19, 1991. Laboratory results and optical
modeling show that the photolysis of forms of solid iron may occur deep into the
ocean's euphotic zone; the availability of iron to phytoplankton in the ocean
may be much greater than previously thought.
Two articles from: Nature, 353(6340), Sep. 12, 1991.
"Estimation of New Production in the Ocean by Compound Remote Sensing,"
S. Sathyendranath (Biol. Oceanog. Div., Bedford Inst. Oceanog., Box 1006,
Dartmouth, N.S. B2Y 4A2, Can.), T. Platt et al., 129-133. An approach that
depends on parameterizations developed from ship observations, as well as on
satellite data, yields more representative estimates of the large-scale average
new production than those calculated from ship data alone.
"Iron Still Comes from Above," a comment on the source of diatomic
iron in the open ocean, p. 123.
"Photochemical Degradation of Dissolved Organic Carbon and Its Impact
on the Oceanic Carbon Cycle," K. Mopper (Rosenstiel Sch. Marine Sci., Univ.
Miami, 4600 Rickenbacker Causeway, Miami FL 33149), X. Zhou et al., Nature,
353(6339), 60-62, Sep. 5, 1991.
Presents new data suggesting that the photochemical degradation of aquatic
humic substances into biologically labile and/or volatile organic compounds is
the rate-limiting step for the removal of a large fraction of DOC, and the rate
will increase with increasing UV-B. Estimates the oceanic residence time of
biologically refractory, photochemically reactive DOC to be 500-2100 years, less
than its apparent 14C age.
"Basin-Scale Estimates of Oceanic Primary Production by Remote
Sensing: The North Atlantic," T. Platt (Biol. Oceanog. Div., Bedford Inst.
Oceanog., Box 1006, Dartmouth, N.S. B2Y 4A2, Can.), C. Caverhill, S.
Sathyendranath, J. Geophys. Res., 96(C8), 15,147-15,159, Aug.
Coastal Zone Color Scanner data were combined with vertical profiles of
chlorophyll and results of photosynthesis-light experiments, and used to test
several different parameterizations necessary for calculating primary
production. In some situations, less complete model versions gave results that
differed by as much as 50% from the benchmark. Results suggest caution in using
biomass as a proxy for primary production, especially outside the tropics.
Remote sensing is the method of choice for calculating primary production at the
"High Turnover Rates of Dissolved Organic Carbon during a Spring
Phytoplankton Bloom," D.L. Kirchman (Marine Sci., Univ. Delaware, Lewes DE
19958), Y. Suzuki et al., Nature, 352(6336), 612-614, Aug. 15,
1991. High estimates of DOC concentrations and turnover rates based on North
Atlantic data suggest changes are needed in models of carbon cycling and of the
ocean's role in buffering increases in atmospheric CO2.
"Importance of Phaeocystis Blooms in the High-Latitude Ocean
Carbon Cycle," W.O. Smith, Jr. (Dept. Botany, Univ. Tennessee, Knoxville TN
37996), L.A. Codispoti et al., ibid., 352(6335), 514-516, Aug.
8, 1991. Results suggest that the Greenland Sea may be a larger sink of
atmospheric CO2 than has been previously thought.
"Top Predators in the Southern Ocean: A Major Leak in the Biological
Carbon Pump," M.E. Huntley (Scripps Inst. Oceanog., Univ. California, La
Jolla CA 92093), M.D.G. Lopez, D.M. Karl, Science, 253(5015),
64-66, July 5, 1991.
Although it has been suggested that primary production and carbon dioxide
uptake of the Southern Ocean could be enhanced by the addition of iron, an
analysis of the food web for these waters implies that they may be remarkably
inefficient as a carbon sink. The large flux of carbon respired to the
atmosphere by top predators, air-breathing birds and mammals, may transfer into
the atmosphere as much as 20-25% of photosynthetically fixed carbon.
Two articles from: Global Biogeochem. Cycles, 5(2), June
"Atmospheric Iron Inputs and Primary Productivity: Phytoplankton
Responses in the North Pacific," R.W. Young (Dept. Marine Sci., Univ. S.
Florida, St. Petersburg FL 33701), K.L. Carder et al., 119-134. Describes major
increases in primary production following pulses of dust transported from Asia.
"Possible Effects of Iron Fertilization in the Southern Ocean on
Atmospheric CO2 Concentration," F. Joos (Phys. Inst., Univ. Bern, CH-3012
Bern, Switz.), U. Siegenthaler, J.L. Sarmiento, 135-150. Results from a
high-latitude exchange/interior diffusion advection model show that the maximum
atmospheric CO2 depletion that would result from fertilization is 58 ppm after
50 years and 107 ppm after 100 years, with an uncertainty estimated to range
from -29% to +17%. The possible effect of fertilization is small compared to CO2
increases expected in the absence of strict control measures.
"Low Iron Requirement for Growth in Oceanic Phytoplankton," W.G.
Sunda (Beaufort Lab., Southeast Fisheries Ctr., Beaufort NC 28516), D.G. Swift,
S.A. Huntsman, Nature, 351(6321), 55-57, May 2, 1991.
Found that an oceanic diatom was able to grow at a near maximum specific
rate of about 1.0 per day at a cellular Fe:C ratio of 2 micro mol:mol, about
2-20% of values previously used to estimate algal Fe requirements in seawater.
Results have important implications for iron limitation of primary productivity.
"A Chemical Method for Estimating the Availability of Iron to
Phytoplankton in Seawater," M.L. Wells (Darling Ctr., Univ. Maine, Walpole
ME 04573), L.M. Mayer, R.R.L. Guillard, Marine Chem., 33(1-2),
23-40, Apr. 1991. A technique that employs the complexing agent
8-hydroxyquinoline (oxine) to measure a labile portion of total Fe in seawater
appears to provide an operational method for estimating the biological
availability of Fe in seawater.
"Marine Biota Effects on the Compositional Structure of the World
Oceans," H.S. Kheshgi (Res. Labs., Exxon Co., Annandale, NJ 08801), B.P.
Flannery, M.I. Hoffert, J. Geophys. Res., 96(C3), 4957-4969,
Mar. 15, 1991. The vertical structure of total carbon, alkalinity, nutrients and
dissolved oxygen in the world oceans is examined with a 1-D box model of the
equatorial and polar oceans.
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