Publication Date:
2022-05-26
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January, 1977
Description:
Particulate matter samples, split into 〈l μm, 1-53 μm, and 〉53 μm
size fractions have been obtained using a Large Volume in situ Filtration
System (LVFS) during the SOUTHLANT expedition, R/V CHAIN 115. Profiles
to 400 m are reported for LVFS Stns. 2 and 4-8. Stns. 4, 5, and 8 (S. E.
Atlantic, coastal waters near Walvis Bay and Cape Town, high biological
productivity); Stns. 6 and 2 (S.E. Atlantic, Walvis Bay region and
equatorial Atlantic, moderate productivity); and Sta. 7 (S.E. Atlantic,
edge of central gyre, low productivity) formed a suite of samples for the
study of the chemical, biological, morpholigical distributions and of the
vertical mass flux of particulate matter as a function of biological
productivity.
All samples were analysed for Na, K, Mg, Ca, carbonate, opal, Sr,
C and N and those from Sta. 2 were further analysed for P, Fe, δ13C, 7Be,
214Bi, 214Pb, (226Ra), 210Po, and 210Pb. Biological distributions of
Acantharia, dinoflagellates, coccolithophorids, Foraminifera, diatoms,
silicoflagellates, Radiolaria, and tintinnids were made by light microscopy
(LM) and augmented by scanning electron microscopy (SEM). Size and
morphological distributions of the 〉53 μm particles, especially
Foraminifera, Acantharia, fecal pellets, and fecal matter have been
determined by LM and SEM.
The particle distributions were controlled at all stations by processes
of production, consumption, fragmentation, and aggregation.
Maxima in organism abundance and particulate mass were generally coincident.
They were found nearest the surface when the mixed layer was absent or
poorly developed, and at the base of the mixed layer at the other stations.
Organism vertical distributions showed consistent features: Acantharia,
and dinoflagellates were always nearest the surface; Foraminifera and
diatoms were shallower than or at the base of the mixed layer; Radiolaria
and tintinnids were found in the upper thermocline. Coccolithophorids
and diatoms were the dominant sources of particulate carbonate and opal
in the near surface waters, coccoliths and diatom fragments, deeper.
Features of the distributions of particulate matter attributed to
the feeding activities of zooplankton were: strong concentration gradients
in organisms, mass, and organic matter; enrichment of the 〉53 μm
fraction with coccoliths causing the steady decrease in 〉53 μm Si/carbonate
ratio with depth from values as high as 45 to values near 1.0 at 400 m;
the decrease in organic content with depth from values near 100 % near the
surface to 50 and 60% at 400 m for the 〈53 and 〉53 μm size fractions;
the fragmentation of most material below 100 m; and the production of
fecal pellets and fecal matter which are carriers of fine material to the
sea floor.
Other features were: the nearly constant organic C/N ratios (7.3±0.5 δ)
found for the 1-53 μm fractions at Stns. 4, 5, 6, and 8 compared with the
steady increase observed at Stns. 2 and 7 with depth; particulate carbon
was rather uniformy distributed below 200 m with concentrations showing
a mild reflection of surface productivity; the 〈1 μC/N and δ13C values
are lower and lighter than the 1-53 μm fraction, perhaps indicative of
the presence of marine bacteria; the Ca/carbonate ratios in most samples
significantly exceeded 1.0, values as high as 2.5 were observed at Sta. 8;
the xs Ca and K have shallow regenerative cycles and contrast with Mg which
is bound to a refractory component of organic matter; based on a organic
C/ xs Ca ratio of 100-200:1 for surfàce samples, the cycling of xs Ca was
calculated to be 1-2 x 1013mol/cm2/y compared with the production of
carbonate, 7±2 x 1013 mol/cm2/y.
Chemical effects noted were: organic matter had both binding capabilities and ion-exchange capacity for major and minor ions present in seawater.
Acantharia (SrS04) dissolve most significantly below 200 m at Sta.2.
The vertical mass fluxes through 400 m at Stas. 2, 5, 6, and 7 were
calculated from size distributions measured in 1 m3 in seawater for
Foramifera, fecal pellets, and fecal matter. Two flux models were
used together with Junge distributions for these calculations. Fecal
matter and Forainifera transported most mass at Stns. 2 and 5 where the
fluxes were between 2 and 3, and 5 and 6 gm/cm2/1000y respectively;
fècal matter, Foramnifera, and fecal pellets contributed equally to
the .9-1.3gm/cm2/1000y flux at Sta. 6; and fecal pellets and Foraminifera
were the carriers of 0.1-0.3 gm/cm2/1000y to the sea floor. Corresponding
chemical fluxes of organic carbon, carbonate, and opal were: 80-90,
11-24, and ~10 mmol/cm2/1000y at Sta. 5; 15-20, 2.7-5.0 and 1.7-2.5
mmol/cm2/1000y at Sta. 6; 1-4, 0.6-1.5, and 0.1-0.3 mmol/cm2/1000y at Sta. 7,
and 40-65, 4.6-7.4, and 4.9-7.9 mmol/cm2/1000y at station 2. Over 90%
of the organic matter produced in the euphotic zone is recycled in the
upper 400 m. The efficiency is nearly 99% in areas of low productivity;
the organic to carbonate carbon ratios are highest at locations where the
flux is greatest as are the Si/carbonate ratios. Besides carbonate, opal, celestite, and other mineral phases, organic matter may be a significant
carrier of minor and trace elements to the deep ocean.
Description:
This work was supported by contract N00014-75-C029l
from the Office of Naval Research and by the Doherty
Foundation.
Keywords:
Marine sediments
;
Particle size determination
;
Particles
;
Chain (Ship : 1958-) Cruise CH115
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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