Stable Isotopes of Pteropod Shells as Recorders of Sub-Surface
Water Conditions: Comparison to the Record ofG. ruber and to
Measured Values
G. Fischerl*,M. Kalberer, B. Donner l and G. Wefer l
I Universitdt Bremen, Fachbereich Geowissenschaften, Postfach 33 04 40,
D-28334 Bremen, Germany
2 Universitdt Bern, Hauptstr. 24, CH-5200 Brugg
*corresponding author (e-mail):g05f@uni-bremen.de
Abstract: We compared a four-year long oxygen and carbon isotope record of the pteropod Limacina
injlata Guveniles) with a record derived from Glohigerinoides ruher (white variety) sampled with
time-series sediment traps off Cape Blanc (Mauretania). Both oxygen isotope records provide seasonal
patterns of water temperatures which generally correspond to measured variations of surface water
temperatures. Surprisingly, adult specimens of L. injlata collected during 1989 also showed a seasonal
oxygen isotope pattern, suggesting rapid shell growth and relatively short lifespans of this species.
Due to its different life and carbonate precipitation habitat, G. ruher generally produces higher water
temperatures (applying -0.35%0 as vital effect) than L. injlata (precipitation depth around 50 m).
Absolute temperatures derived from G. ruher at times exceeded the measured SSTs when applying
a vital effect of -0.35%0. All temperature curves show changing seasonality from year-to-year:
seasonality in temperature was highest in 1989 and lowest in 1991. During 1991, calculated temperatures
remain generally low and the reconstructed temperature curves of G. ruher and L. injlata converge,
suggesting stronger and deeper mixing of water masses. The seasonal onc patterns of juvenile L.
injlata and G. ruher differ largely, the former species revealing higher values of up to 1.5%0. Unlike
G. ruher, L. injlata shows a negative temperature dependency of onc of 0.08%0 per I CC. The
temperature-corrected onc record of L. injlata corresponds better (compared to G. ruher) to seasonal
variations in carbon flux which in tum largely determines the onc oO::CO, in water masses near the
surface. Furthermore, the corrected onC values of this pteropod correspond better to measured
onC LCO, values.
Introduction
The fossil record of shelled pteropods extends back foraminifera, they show distinct water mass preto the Cretaceous and has been used to reconstruct ferences and most pteropods occur in the tropics
past hydrography (see Herman 1978, and refer- and subtropics. Recently, several sediment trap inences therein). These epi- and mesopelagic organ- vestigations have contributed to our knowledge on
isms which consume zoo- and phytoplankton are the seasonal distribution of pteropods in the surface
common and widespread in the surface plankton and subsurface waters (Almogi-Labin et al. 1988;
ofthe world ocean (Van der Spoe11967; Be and Bathmann et al. 1991; Fabry and Deuser 1992;
Gillmer 1977) and shell masses in the ocean's sur- Kalberer et al. 1993). The longest pteropod flux and
face waters may be as high as those of planktonic isotope record so far obtained was provided by
foraminifera. Most species live within the upper few Jasper and Deuser (1993) suggesting that pteropod
hundred meters of the water column except some shell fluxes respond to the annual cycle in primary
bathypelagic species living in depths greater than production in the upper water column of the
500 m. Like other planktonic organisms, such as Sargasso Sea.
From FISCHER G, WEFER G (eds), 1998, Use o/Proxies in Paleoceanography: Examples/rom the South Atlanlic.Springer-Verlag
Berlin Heidelberg, pp 191-206
Water Conditions: Comparison to the Record ofG. ruber and to
Measured Values
G. Fischerl*,M. Kalberer, B. Donner l and G. Wefer l
I Universitdt Bremen, Fachbereich Geowissenschaften, Postfach 33 04 40,
D-28334 Bremen, Germany
2 Universitdt Bern, Hauptstr. 24, CH-5200 Brugg
*corresponding author (e-mail):g05f@uni-bremen.de
Abstract: We compared a four-year long oxygen and carbon isotope record of the pteropod Limacina
injlata Guveniles) with a record derived from Glohigerinoides ruher (white variety) sampled with
time-series sediment traps off Cape Blanc (Mauretania). Both oxygen isotope records provide seasonal
patterns of water temperatures which generally correspond to measured variations of surface water
temperatures. Surprisingly, adult specimens of L. injlata collected during 1989 also showed a seasonal
oxygen isotope pattern, suggesting rapid shell growth and relatively short lifespans of this species.
Due to its different life and carbonate precipitation habitat, G. ruher generally produces higher water
temperatures (applying -0.35%0 as vital effect) than L. injlata (precipitation depth around 50 m).
Absolute temperatures derived from G. ruher at times exceeded the measured SSTs when applying
a vital effect of -0.35%0. All temperature curves show changing seasonality from year-to-year:
seasonality in temperature was highest in 1989 and lowest in 1991. During 1991, calculated temperatures
remain generally low and the reconstructed temperature curves of G. ruher and L. injlata converge,
suggesting stronger and deeper mixing of water masses. The seasonal onc patterns of juvenile L.
injlata and G. ruher differ largely, the former species revealing higher values of up to 1.5%0. Unlike
G. ruher, L. injlata shows a negative temperature dependency of onc of 0.08%0 per I CC. The
temperature-corrected onc record of L. injlata corresponds better (compared to G. ruher) to seasonal
variations in carbon flux which in tum largely determines the onc oO::CO, in water masses near the
surface. Furthermore, the corrected onC values of this pteropod correspond better to measured
onC LCO, values.
Introduction
The fossil record of shelled pteropods extends back foraminifera, they show distinct water mass preto the Cretaceous and has been used to reconstruct ferences and most pteropods occur in the tropics
past hydrography (see Herman 1978, and refer- and subtropics. Recently, several sediment trap inences therein). These epi- and mesopelagic organ- vestigations have contributed to our knowledge on
isms which consume zoo- and phytoplankton are the seasonal distribution of pteropods in the surface
common and widespread in the surface plankton and subsurface waters (Almogi-Labin et al. 1988;
ofthe world ocean (Van der Spoe11967; Be and Bathmann et al. 1991; Fabry and Deuser 1992;
Gillmer 1977) and shell masses in the ocean's sur- Kalberer et al. 1993). The longest pteropod flux and
face waters may be as high as those of planktonic isotope record so far obtained was provided by
foraminifera. Most species live within the upper few Jasper and Deuser (1993) suggesting that pteropod
hundred meters of the water column except some shell fluxes respond to the annual cycle in primary
bathypelagic species living in depths greater than production in the upper water column of the
500 m. Like other planktonic organisms, such as Sargasso Sea.
From FISCHER G, WEFER G (eds), 1998, Use o/Proxies in Paleoceanography: Examples/rom the South Atlanlic.Springer-Verlag
Berlin Heidelberg, pp 191-206