154
Land-Ocean SYstems in the Siberian Arctic: Dynamics and History
Areas showing different stages of new ice formation were studied in the Laptev Sea during
the late freeze-up period in October 1995. In the present study, special emphasis was layed on
the following questions: Which pigment concentrations (Chi a and phaeopigments) as
indicators of algal biomass occur in the water column, new ice, nilas and young ice during the
freeze-up period? Which biomass can be found in the newly forming ice sheet compared to the
standing stock in the water column?
Material and methods
During the Transdrift III expedition on lIB "Kapitan Dranitsyn" (1.10.- 30.10.1995), water
samples as well as samples of new and young ice were collected. Informations about ice cover
during the expedition are given in Aleksandrov and Kolatschek (1997) and Lindemann et al.
(this volume). Different ice types were classified according to the WMO Sea-Ice Nomenclature
(1970). Discrimination between "clean" and "dirty" sea ice was carried out by optical
examination, whereas particle-stained "dirty" ice showed sediment concentrations of 10 mg 1 -1
at least during this expedition (F. Lindemann, pers. comm.). Further informations on ship and
ice stations are listed in the cruise report (Kassens, 1997).
Water samples were taken at selected depth (0 m, 5 m, 10m, 15 m, 20 m, 30 m; down to the
sea floor) using a Niskin sampler. Sub-ice water was sampled by means of 11 plastic containers
opened under the ice from drilled or hacked holes. Ice samples were taken by a ladle or 11
plastic containers (grease ice) or collected in plastic buckets (pancake ice, nilas) and allowed to
melt in the dark at 4°C. Cores from ice floes thicker than 10 cm were taken with an ice auger
and cut into sections for subsequent processing (sections were measured individually). All
samples were filtered on GFIF filters, stored frozen and analysed for Chi a and phaeopigments
according to Arar and Collins (1992) using a Turner design fluorometer. Water samples taken
during Transdrift I (2.8.-5.10.1993; R/V "Ivan Kireyev") were obtained with identical
procedures but analysed photometrically according to Jeffrey and Humphrey (1975). Further
informations about this cruise are given in Kassens and Karpiy (1994).
Results and discussion
Standing stock
Phytoplankton biomass expressed as Chi a integrated over the entire water column was lower
than 7.3 mg m- 2 at most stations but reached a maximum in a polynya in Buor Khaya Bay
(15.9 and 9.7 mg m- 2 at St. 32 and 33, respectively; Figure 1). In comparison, values of the
standing stock in August/September 1993 ranged from 1.2 mg m- 2 northwest off the island of
Belkovsky to 25.7 mg m- 2 northeast of the Lena outflow. The observed pattern cannot be
explained by different integration depth (overall 14 - 40 m in autumn 1995), since the areas
showing high biomass were shallow (14 and 15 m st St. 32 and 33).
A maximum of Chi a in the Buor Khaya area was also reported by Heiskanen and Keck
(1996) in September 1991, although they suggested because of low ChI a and high
phaeopigment concentrations that the phytoplankton community was already in a senescent
phase or affected by grazing in other areas of the Laptev Sea. Our findings showed that Chi a
concentrations as high as measured in the summer period can also be found in October. Similar
Chi a biomass had been reported from the end of the growth season in ice-covered areas of the
Barents Sea (10.1 to 14.7 mg m- 2 ; Hegseth, 1997). Summer and autumn values from the
Laptev Sea lay within the lower range of Chlorophyll concentrations from productive regions of
the Canadian Arctic, integrated over the photic zone (summerized by Demers et a!., 1986).
Land-Ocean SYstems in the Siberian Arctic: Dynamics and History
Areas showing different stages of new ice formation were studied in the Laptev Sea during
the late freeze-up period in October 1995. In the present study, special emphasis was layed on
the following questions: Which pigment concentrations (Chi a and phaeopigments) as
indicators of algal biomass occur in the water column, new ice, nilas and young ice during the
freeze-up period? Which biomass can be found in the newly forming ice sheet compared to the
standing stock in the water column?
Material and methods
During the Transdrift III expedition on lIB "Kapitan Dranitsyn" (1.10.- 30.10.1995), water
samples as well as samples of new and young ice were collected. Informations about ice cover
during the expedition are given in Aleksandrov and Kolatschek (1997) and Lindemann et al.
(this volume). Different ice types were classified according to the WMO Sea-Ice Nomenclature
(1970). Discrimination between "clean" and "dirty" sea ice was carried out by optical
examination, whereas particle-stained "dirty" ice showed sediment concentrations of 10 mg 1 -1
at least during this expedition (F. Lindemann, pers. comm.). Further informations on ship and
ice stations are listed in the cruise report (Kassens, 1997).
Water samples were taken at selected depth (0 m, 5 m, 10m, 15 m, 20 m, 30 m; down to the
sea floor) using a Niskin sampler. Sub-ice water was sampled by means of 11 plastic containers
opened under the ice from drilled or hacked holes. Ice samples were taken by a ladle or 11
plastic containers (grease ice) or collected in plastic buckets (pancake ice, nilas) and allowed to
melt in the dark at 4°C. Cores from ice floes thicker than 10 cm were taken with an ice auger
and cut into sections for subsequent processing (sections were measured individually). All
samples were filtered on GFIF filters, stored frozen and analysed for Chi a and phaeopigments
according to Arar and Collins (1992) using a Turner design fluorometer. Water samples taken
during Transdrift I (2.8.-5.10.1993; R/V "Ivan Kireyev") were obtained with identical
procedures but analysed photometrically according to Jeffrey and Humphrey (1975). Further
informations about this cruise are given in Kassens and Karpiy (1994).
Results and discussion
Standing stock
Phytoplankton biomass expressed as Chi a integrated over the entire water column was lower
than 7.3 mg m- 2 at most stations but reached a maximum in a polynya in Buor Khaya Bay
(15.9 and 9.7 mg m- 2 at St. 32 and 33, respectively; Figure 1). In comparison, values of the
standing stock in August/September 1993 ranged from 1.2 mg m- 2 northwest off the island of
Belkovsky to 25.7 mg m- 2 northeast of the Lena outflow. The observed pattern cannot be
explained by different integration depth (overall 14 - 40 m in autumn 1995), since the areas
showing high biomass were shallow (14 and 15 m st St. 32 and 33).
A maximum of Chi a in the Buor Khaya area was also reported by Heiskanen and Keck
(1996) in September 1991, although they suggested because of low ChI a and high
phaeopigment concentrations that the phytoplankton community was already in a senescent
phase or affected by grazing in other areas of the Laptev Sea. Our findings showed that Chi a
concentrations as high as measured in the summer period can also be found in October. Similar
Chi a biomass had been reported from the end of the growth season in ice-covered areas of the
Barents Sea (10.1 to 14.7 mg m- 2 ; Hegseth, 1997). Summer and autumn values from the
Laptev Sea lay within the lower range of Chlorophyll concentrations from productive regions of
the Canadian Arctic, integrated over the photic zone (summerized by Demers et a!., 1986).