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sediments (the latter affects benthic activity), particle
size, adsorption to mineral surfaces and sediment
porosity.
Although the fraction of organic matter burried in
sediments is small relative to the amount produced by
photosynthesis in oceanic surface waters, empirical
relationships were derived from the analysis of
sedimentary organic matter to estimate oceanic
paleoproductivity (PaP [g C m
-2
yr
-1
]) in the geological
past:
PaP = C·ρ(100-φ/100)/0.003·S 0.3
(4.1)
In this equation of Müller and Suess (1979), the
Pleistocene paleoproductivity of the (oxic) ocean is
related to the organic carbon content of a sediment in
percent dry weight (C), the density of the dry sediment
(ρ; g cm
-3
), its porosity (φ; %) and the linear bulk
sedimentation rate (S; cm of total sediment per 1000 yr).
The exponential factor was obtained from calibration
with data from the present ocean. Because it was shown
later that the organic carbon accumulation rate is a
function of the carbon flux near the seafloor, which is
related to both productivity and water depth, Stein
(1986a, 1991) derived a more complex empirical
relationship using flux data of Betzer et al. (1984):
PaP = 5.31[C(ρ WB - 1.026φ/100)] 0.71 ·S 0.07 ·D 0.45
(4.2)
with ρ WB being the wet bulk density of the sediment
and D the water depth. Values from this equation are
proportional, although numerically not identical, to the
results obtained from a third empirical relationship
developed by Sarnthein et al. (1987, 1988):
Fig.4.3 Schematic representation of organic matter flux to the ocean bottom.
4.2
Organic Matter Accumulation in Sediments