Distribution of Aquatic Palynomorphs in Surface Sediments from
the Laptev Sea, Eastern Arctic Ocean
M. Kunz·Pirrung
A lfred-Wegener-Institutfiir Polar- und Meeresforschung, Postfach 120161, D 27515 Bremerhaven, Germany.
Received II March 1997 and accepted in revised form 5 March 1998
Abstract - Aquatic palynomorphs were studied in surface sediments from the Laptev Sea
shelf and the adjacent continental slope. The Laptev Sea is characterized by a strong salinity
gradient owing to an extreme freshwater influx from the Siberian rivers in summer. The
assemblages are composed of various organic-walled microfossils, in particular
dinoflagellate cysts, chlorococcalean algae, acritarchs and several groups of zoomorphs. The
species composition and the distribution pattern of dinoflagellate cysts and chlorococcalean
algae is related to the salinity gradient of the surface water from the coast to the continental
slope. A distinct change in the dinoflagellate cyst assemblages occurs across the continental
slope corresponding roughly to a salinity interval of 28 to 30. Assemblage I from the shelf
is dominated by Brigantedinium spp., Alfiidasphaeridium? minutum and related
morphotypes. Impagidinium? pallidum, Nematosphaeropsis labyrinthus and
Operculodinium centrocarpum characterize assemblage II from the continental slope. The
chlorococcalean algae assemblages are composed of Pediastrum spp. and Botryococcus cf.
braunii which usually live in freshwater. Therefore, their occurrence in the marine
environment reflects the freshwater discharge into the Laptev Sea. The strong gradient in
chlorococcalean algae concentrations suggests that the influence of freshwater is confined
mainly to the shelf.
Introduction
The Laptev Sea is one of the most important sea-ice source areas for the Arctic Ocean. Large
amounts of sea ice are produced here during the winter months (e.g., Kassens and Karpiy
1994b). This ice cover affects the surface circulation in the Arctic by restricting the heat
exchange between the ocean and the atmosphere. The ice masses, which can be sediment-laden,
are transported with the Transpolar Drift across the Arctic Ocean (Figure I) and exit through the
Fram Strait into the Greenland and Iceland seas (Dethleff et a!., 1993). In these areas the sea ice
melts out in spring and summer.
The Laptev Sea is a broad shelf area with an average water depth of less than 50 to 60 meters.
Five south to north oriented submarine valleys cross the shelf (Holmes and Creager, 1974) and
link the mouths of the large Siberian rivers Khatanga, Anabar, Olenek, Lena and Yana with the
continental slope. These rivers are very important for the hydrographic conditions in the Laptev
Sea and the Arctic Ocean. During the short Arctic summer, enormous amounts of freshwater are
discharged into the Laptev Sea. Therefore, sea-surface salinities show a strong gradient (Figure
2) from the river mouths to the continental slope, increasing from approximately 6 to 30 in
summer (Dmitrenko et a!., 1994; Treshnikov, I 985). These surface water masses are underlain
by more saline water masses with an average salinity of approximately 34.
Within the Russian-German multidisciplinary research projekt "Laptev Sea System"
planktonic microfossils, especially diatoms (Cremer, 1998) and palynomorphs are investigated
in order to provide paleoenvironmental information about changes in surface water mass
distribution and freshwater discharge during the Holocene. In particular, dinoflagellate cysts
(e.g., Mudie, 1992; De Vernal et a!., 1994, 1996; Matthiessen, 1996) and chlorococcalean
algae are important tools for paleoceanographic reconstructions in high-latitude marine
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999,561-575.
the Laptev Sea, Eastern Arctic Ocean
M. Kunz·Pirrung
A lfred-Wegener-Institutfiir Polar- und Meeresforschung, Postfach 120161, D 27515 Bremerhaven, Germany.
Received II March 1997 and accepted in revised form 5 March 1998
Abstract - Aquatic palynomorphs were studied in surface sediments from the Laptev Sea
shelf and the adjacent continental slope. The Laptev Sea is characterized by a strong salinity
gradient owing to an extreme freshwater influx from the Siberian rivers in summer. The
assemblages are composed of various organic-walled microfossils, in particular
dinoflagellate cysts, chlorococcalean algae, acritarchs and several groups of zoomorphs. The
species composition and the distribution pattern of dinoflagellate cysts and chlorococcalean
algae is related to the salinity gradient of the surface water from the coast to the continental
slope. A distinct change in the dinoflagellate cyst assemblages occurs across the continental
slope corresponding roughly to a salinity interval of 28 to 30. Assemblage I from the shelf
is dominated by Brigantedinium spp., Alfiidasphaeridium? minutum and related
morphotypes. Impagidinium? pallidum, Nematosphaeropsis labyrinthus and
Operculodinium centrocarpum characterize assemblage II from the continental slope. The
chlorococcalean algae assemblages are composed of Pediastrum spp. and Botryococcus cf.
braunii which usually live in freshwater. Therefore, their occurrence in the marine
environment reflects the freshwater discharge into the Laptev Sea. The strong gradient in
chlorococcalean algae concentrations suggests that the influence of freshwater is confined
mainly to the shelf.
Introduction
The Laptev Sea is one of the most important sea-ice source areas for the Arctic Ocean. Large
amounts of sea ice are produced here during the winter months (e.g., Kassens and Karpiy
1994b). This ice cover affects the surface circulation in the Arctic by restricting the heat
exchange between the ocean and the atmosphere. The ice masses, which can be sediment-laden,
are transported with the Transpolar Drift across the Arctic Ocean (Figure I) and exit through the
Fram Strait into the Greenland and Iceland seas (Dethleff et a!., 1993). In these areas the sea ice
melts out in spring and summer.
The Laptev Sea is a broad shelf area with an average water depth of less than 50 to 60 meters.
Five south to north oriented submarine valleys cross the shelf (Holmes and Creager, 1974) and
link the mouths of the large Siberian rivers Khatanga, Anabar, Olenek, Lena and Yana with the
continental slope. These rivers are very important for the hydrographic conditions in the Laptev
Sea and the Arctic Ocean. During the short Arctic summer, enormous amounts of freshwater are
discharged into the Laptev Sea. Therefore, sea-surface salinities show a strong gradient (Figure
2) from the river mouths to the continental slope, increasing from approximately 6 to 30 in
summer (Dmitrenko et a!., 1994; Treshnikov, I 985). These surface water masses are underlain
by more saline water masses with an average salinity of approximately 34.
Within the Russian-German multidisciplinary research projekt "Laptev Sea System"
planktonic microfossils, especially diatoms (Cremer, 1998) and palynomorphs are investigated
in order to provide paleoenvironmental information about changes in surface water mass
distribution and freshwater discharge during the Holocene. In particular, dinoflagellate cysts
(e.g., Mudie, 1992; De Vernal et a!., 1994, 1996; Matthiessen, 1996) and chlorococcalean
algae are important tools for paleoceanographic reconstructions in high-latitude marine
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999,561-575.