Organic Carbon and Carbonate as Paleoproductivity Proxies
319
Proxies of Paleoproductivity
Numerous proxies have been used to determine
paleoproductivity. Recent developments have focused on biogenic remnants such as organic carbon, carbonate, opal, or biomarkers (specific organic compounds) which are preserved in the deepsea sediment record. Together with barium (see
Gingele et al. this volume) and other trace metals
such as cadmium and copper, or scavenged
radionuclides such as 230Th (see Frank et al. this
volume, Walter et al. this volume), which are related to biological productivity, these sedimentary
components can be summarized as flux proxies
(Berger et al. 1994). Another group of tracers are
those which represent nutrient concentrations (dissolved nitrogen and phosphorus in sea water).
These are, for example, stable isotope ratios of carbon (l3CI'2C) in calcareous shells (see Mulitza et
al. this volume) and of nitrogen C 5 N/14N) in
particulate organic matter (see Holmes et al. this
volume) as well as CdiCa ratios in foraminiferal
calcite (Boyle 1988a). According to Berger et al.
(1994), a third group of paleoproductivity estimators can be classified as trophic proxies, namely
species compositions of foraminifera (see Hale and
Pflaum ann this volume), diatoms, or any other of
such groups containing information about the
trophic structure of the pelagic environment. Principle aspects concerning primary production and
paleoproductivity were reviewed in a report summarizing the proceedings of a Dahlem workshop
on that topic (Berger et al. 1989a). Comprehensive
summaries on the application and limitations of the
various groups of paleoproductivity indicators were
given by Bruland et al. (1989), Herbert et al. (1989),
Elderfield (1990), Berger and Herguera (1992),
Berger et al. (1994), De Lange et al. (1994), Jahn~e
and Shimmield (1995) and Pisias et al. (1995) mcluding references with more detailed information
on each single proxy.
Glacial-to-Holocene Changes of
Paleoproductivity
To fmd out how the efficiency of the biological pump
has changed from a cold to a warm climatic stage,
it is important to evaluate the modification of the
productivity pattern. A comparison between glacial
and Holocene paleoproductivities of the different
ecological domains of the world's oceans, estimated
from various proxies, was compiled by Berger et
al. (1994):
1. Eastern boundary upwelling regions and the
western Arabian Sea. Paleoproductivity increased
during the last Glacial in the eastern boundary
upwelling regions of the Atlantic and Pacifi~ due
to an intensification of wind-controlled upwellmg or
other sources of nutrient supply, such as riverdischarge (Prell and Curry 1981; MUlier et al. 1983;
Sarntheinetal.1982, 1987, 1988;LyleetaI.1988;
Schneider et al. 1996). Comparably low paleoproductivity during this period was reported by
Diester-Haass (1985) for the Walvis Ridge area.
Schrader and Sorknes (1991) and Biebow (1996)
showed that paleoproductivity decreased off Peru
north of 12°S during the last Glacial, whereas
upwelling intensity increased south of this latitude
(DeVries and Schrader 1981; Reimers and Suess
1983). Bertrand et al. (1996) and Gardner et al.
(1997) emphasized the spatial hete~ogeneity. of
paleoproductivity within ocean margm upwe~h~g
systems. They found areas of high paleoproductiVity
co-existing close to others with lower paleoproductivity off Northwest Africa and off California and
attributed this heterogeneity to differences in wind
stress intensity. In contrast to the eastern boundary upwelling regions, paleoproductivity decreased
during the last Glacial in the upwelling system of
the western Arabian Sea due to a weakening of the
SW monsoon (Weedon and Shimmield 1991;
Anderson and Prell 1993).
2. Equatorial divergence zones. Upwelling ~Io~g
the equator, was elevated during the last Glac181 m
both the Atlantic and Pacific Ocean, particularly in
the eastern parts of the ocean basins (Pedersen
1983; Stabe1l1986; Pokras 1987; Lyle et al. 1988;
Lyle 1988; Herguera and Berger 1991; Mix 1989;
Pedersen et al. 1991; Verardo and MyIntyre 1994;
Schneider et al. 1996).
3. Polar oceans. The high productivity zone south
of the modern Antarctic polar frontal zone migrated
northward during the last Glacial due to the expansion of summer sea-ice (Mortlock et al. 1991;
Kumar et al. 1993; Shemesh et al. 1993; Mackensen
et al. 1994; Frank et al. 1996). The level of
319
Proxies of Paleoproductivity
Numerous proxies have been used to determine
paleoproductivity. Recent developments have focused on biogenic remnants such as organic carbon, carbonate, opal, or biomarkers (specific organic compounds) which are preserved in the deepsea sediment record. Together with barium (see
Gingele et al. this volume) and other trace metals
such as cadmium and copper, or scavenged
radionuclides such as 230Th (see Frank et al. this
volume, Walter et al. this volume), which are related to biological productivity, these sedimentary
components can be summarized as flux proxies
(Berger et al. 1994). Another group of tracers are
those which represent nutrient concentrations (dissolved nitrogen and phosphorus in sea water).
These are, for example, stable isotope ratios of carbon (l3CI'2C) in calcareous shells (see Mulitza et
al. this volume) and of nitrogen C 5 N/14N) in
particulate organic matter (see Holmes et al. this
volume) as well as CdiCa ratios in foraminiferal
calcite (Boyle 1988a). According to Berger et al.
(1994), a third group of paleoproductivity estimators can be classified as trophic proxies, namely
species compositions of foraminifera (see Hale and
Pflaum ann this volume), diatoms, or any other of
such groups containing information about the
trophic structure of the pelagic environment. Principle aspects concerning primary production and
paleoproductivity were reviewed in a report summarizing the proceedings of a Dahlem workshop
on that topic (Berger et al. 1989a). Comprehensive
summaries on the application and limitations of the
various groups of paleoproductivity indicators were
given by Bruland et al. (1989), Herbert et al. (1989),
Elderfield (1990), Berger and Herguera (1992),
Berger et al. (1994), De Lange et al. (1994), Jahn~e
and Shimmield (1995) and Pisias et al. (1995) mcluding references with more detailed information
on each single proxy.
Glacial-to-Holocene Changes of
Paleoproductivity
To fmd out how the efficiency of the biological pump
has changed from a cold to a warm climatic stage,
it is important to evaluate the modification of the
productivity pattern. A comparison between glacial
and Holocene paleoproductivities of the different
ecological domains of the world's oceans, estimated
from various proxies, was compiled by Berger et
al. (1994):
1. Eastern boundary upwelling regions and the
western Arabian Sea. Paleoproductivity increased
during the last Glacial in the eastern boundary
upwelling regions of the Atlantic and Pacifi~ due
to an intensification of wind-controlled upwellmg or
other sources of nutrient supply, such as riverdischarge (Prell and Curry 1981; MUlier et al. 1983;
Sarntheinetal.1982, 1987, 1988;LyleetaI.1988;
Schneider et al. 1996). Comparably low paleoproductivity during this period was reported by
Diester-Haass (1985) for the Walvis Ridge area.
Schrader and Sorknes (1991) and Biebow (1996)
showed that paleoproductivity decreased off Peru
north of 12°S during the last Glacial, whereas
upwelling intensity increased south of this latitude
(DeVries and Schrader 1981; Reimers and Suess
1983). Bertrand et al. (1996) and Gardner et al.
(1997) emphasized the spatial hete~ogeneity. of
paleoproductivity within ocean margm upwe~h~g
systems. They found areas of high paleoproductiVity
co-existing close to others with lower paleoproductivity off Northwest Africa and off California and
attributed this heterogeneity to differences in wind
stress intensity. In contrast to the eastern boundary upwelling regions, paleoproductivity decreased
during the last Glacial in the upwelling system of
the western Arabian Sea due to a weakening of the
SW monsoon (Weedon and Shimmield 1991;
Anderson and Prell 1993).
2. Equatorial divergence zones. Upwelling ~Io~g
the equator, was elevated during the last Glac181 m
both the Atlantic and Pacific Ocean, particularly in
the eastern parts of the ocean basins (Pedersen
1983; Stabe1l1986; Pokras 1987; Lyle et al. 1988;
Lyle 1988; Herguera and Berger 1991; Mix 1989;
Pedersen et al. 1991; Verardo and MyIntyre 1994;
Schneider et al. 1996).
3. Polar oceans. The high productivity zone south
of the modern Antarctic polar frontal zone migrated
northward during the last Glacial due to the expansion of summer sea-ice (Mortlock et al. 1991;
Kumar et al. 1993; Shemesh et al. 1993; Mackensen
et al. 1994; Frank et al. 1996). The level of