Recent diatom distributions in the Amundsen Sea
Recent diatom distributions in the Amundsen Sea D.E. KELLOGG and T.B. KELLOGG Institute for Quaternary Studies
and
Department of Geological Sciences University of Maine Orono, Maine 04469
We summarize here the results of diatom analyses of water, sediment, and sea-ice samples collected during a cruise of the U.S. Coast Guard icebreaker Glacier to the Amundsen Sea in January of 1985 (T. Kellogg, D. Kellogg, and Hughes 1985). This work, described in greater detail by D. Kellogg and T. Kellogg (in preparation) is the first study of modern Amundsen Sea microfossil distributions and will serve as the basis for interpretation of sediment cores in terms of past oceanographic, glacial, and climatic fluctuations (D. Kellogg and T. Kellogg, Antarctic Journal, this issue). Sample locations are shown in a companion paper in this volume (D. Kellogg and T. kellogg, Antarctic Journal, this issue, figure 1). Marine diatoms in sediments. Fifty-seven marine taxa were identified in the core-top samples (42 to the species level), but most of these taxa occur only rarely (1-5 specimens per sample). Species that were present consistently in most samples, often in moderate to high abundance (more than 10 specimens per sample) include: Actinocyclus actinochilus, Chactoceros sp. spores, Eucampia antarctica, Paralia sol, Nitzschia curta, N. kerguelensis, N. vanheurckii, N. obliquecostata, N. sublineata, and Thalassiosira gra-
cilis. Present in lower abundance were various species of the genra Cocconeis and Thalassiosira. All but two of the marine species recorded are extant in modern antarctic waters or occur in Recent antarctic sediments (e.g., Fenner, Schrader, and Wienigk 1976; Truesdale and Kellogg 1979). These species are typical of McCollum's (1975) Thalassiosira lentiginosa (formerly Coscinodiscus lentiginosus) Parital Range Zone. The two exceptions are Denticulopsis hustedtii and Trinacria pileolus, both of which occur as single specimens in DF85-111 and DF85-96, respectively. These species have stratigraphic ranges inthe Miocene (McCollum 1975) to Pliocene (Ciesielski 1983; Burckle personal communication). Their presence in Amundsen Sea core-top samples suggests either reworking or the exposure of older sediment on the sea floor. Reworking is more likely for both samples because they contain the Quaternary species N. curta and the Quaternary/upper Pliocene species A. actinochilus in abundance (D. Kellogg and T. Kellogg 1986b). Nonmarine diatoms in sediments. Nonmarine diatoms are present in most sediment samples, but abundances are generally much lower than those of marine species and usually consist of only one or two specimens of each species. Taxa recorded include Melosira distans, and species of Cyclotella, Diploneis, Navicula, and Tabellaria. The nonmarine species appear to be distributed nearly uniformly throughout the Amundsen Sea core tops, with slightly higher abundances in cores DF85-95 and DF85-99. Our report of nonmarine diatoms in Amundsen Sea sediments is not anomalous. Many of these same species occur, in comparable abundances, in Ross Sea sediments (T. Kellogg and Truesdale 1979; Truesdale and Kellogg 1979; T. Kellogg and D. 1986 REVIEW
Kellogg 1981). These nonmarine species are widespread in lakes and melt ponds throughout the ice-free valleys of southern Victoria Land (D. Kellogg et al. 1980), on the McMurdo Ice Shelf (D. Kellogg and T. Kellogg 1984, in press), and in the Vestfold Hills (Setty, D. Kellogg, and T. Kellogg 1984). Melt pools occurring on antarctic sea ice could also provide a suitable habitat for nonmarine diatoms throughout the circumantarctic sea-ice zone. Introduction of nonmarine diatoms to marine sediments requires only melting of the pack ice. Once they are introduced to the water column, currents may carry diatoms even beneath ice shelves and floating glacier tongues, such as Pine Island Glacier. Diatoms in ice and water samples. Additional material was collected for comparison of fossil and living diatom distributions. Sea-water samples were obtained routinely at each coring station, and ice samples were collected intermittently. All ice analyzed was stained green or red by algal material. Sea water and melted ice were filtered to extract diatoms. Filters (cleared with acetic acid) were mounted on slides using Hyrax. All our ice and water samples contained abundant marine diatoms and were dominated by large to very large numbers of N. cylindrus, Nitzchia curta, N. vanheurckii, and N. obliquecostata, in varying proportions, were subdominants in most samples. These four species together usually comprised over 95 percent of each sample in our quantitative analyses, and a total of 300 specimens was almost always obtained after analyzing only a small portion of each slide. The overwhelming dominance in ice and water samples of N. cylindrus may be attributed to a seasonal bloom, because all these samples were collected within 1 week and because they cover almost the entire north-south extent of the eastern Amundsen Sea. Other species which are known to spend part of their life cycle attached to the underside of the sea ice (e.g., N. curta, N. kerguelensis, and N. vanheurckii are, predictably, subdominants. More than half of the sea-ice and sea-water samples contained occasional specimens of nonmarine diatoms. One sample (DF85-73-55) had nearly 50 specimens of a small delicate species of Navicula which we have not encountered previously but which we suspect is nonmarine, as are most members of that genus. Nonmarine diatoms in sea-ice samples may represent populations that inhabit small melt pools or occur at the base of the snow layer (i.e., in situ assemblages), or they may have been carried from some terrestrial location by winds. The low abundances of nonmarine diatoms in our ice samples (except DF85-73-55) suggest that they represent a contaminant and were probably introduced by winds. Scattered occurrences of nonmarine diatoms in surface water samples probably also result from distribution by winds. We also sampled melt ponds on islands in the Amundsen Sea, to determine if nonmarine species present in this area are similar to those in the Ross Sea sector and elsewhere. Samples were collected from open water in ponds on the Lindsey and Edwards Islands. Both these samples were dominated by the marine species N. cylindrus, although nonmarine species comprised 22.4 percent of the diatom flora at the Lindsey Islands. We suspect that marine species are introduced to these ponds by storm waves and spray, an hypothesis that is supported by the lower percentage of marine species at the higher elevation Lindsey Islands site. Nonmarine diatoms at the Lindsey Islands are dominated by formae of the species Navicula muticopsis, which occur commonly in similar melt ponds in the ice-free valleys of southern Victoria Land and on the McMurdo Ice Shelf (D. Kellogg et al. 1980; D. Kellogg and T. Kellogg in press). The 161
same small delicate Navicula species we noted in the ice sample at DF85-74-55 was also found in both terrestrial ponds samples. We conclude that both these sites are situated too close to the sea to give an accurate representation of a typical nonmarine diatom flora for the area surrounding the Amundsen Sea. We thank Captain W. Hewell and the officers and crew of U.S. Coast Guard icebreaker Glacier, Terence Hughes, and John Anderson and his students, who assisted with our coring project in January 1985. Dennis Cassidy assisted with sampling the cores. David Thompson and Stephanie Staples assisted with sample preparation. This work was supported by National Science Foundation grant DPP 80-20000. References Burckle, L.H. 1985. Personal communication. Ciesielski, P.R 1983. The Neogene and Quaternary diatom biostratigraphy of Subantarctic sediments, Deep Sea Drilling Project Leg 71. Initial Reports of the Deep Sea Drilling Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office. Fenner, J . , H.-J. Schrader, and H. Wienigk. 1976. Diatom phytoplankton studies in the Southern Pacific Ocean, composition and correlation to the Antarctic Convergence and its paleoecological significance. initial Reports of the Deep Sea Drilling Project, Vol. 35. Washington, D.C.: U.S. Government Printing Office. Kellogg, D.E., and T.B. Kellogg. 1984. Diatoms from the McMurdo Ice Shelf, Antarctica. Antarctic Journal of the U.S., 19(5), 76-77. Kellogg, D.E., and T.B. Kellogg. 1986a. Biotic provinces in modern Amundsen Sea sediments: Implications for glacial history. Antarctic Journal of the U.S., 21(5).
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Kellogg, D.E., and T. B. Kellogg. 1986b. Diatom biostratigraphy of sediment cores from beneath the Ross Ice Shelf. Micropaleontology, 32, 74-94. Kellogg, D.E., and T.B. Kellogg. In preparation. Microfossil distributions in modern Amundsen Sea sediments. Palaeogeography, Palaeoclimatology, Palaeoecology.
Kellogg, D.E., and T.B. Kellogg. In press. Diatoms of the McMurdo Ice Shelf, Antarctica: Implications for sediment and biotic reworking. Palaeogeography, Palaeoclirnatology, Palaeoecology.
Kellogg, D.E., M. Stuiver, T.B. Kellogg, and G.H. Denton. 1980. Nonmarine diatoms from late Wisconsin perched deltas in Taylor Valley, Antarctica. Palaeogeography, Palaeocli,natology, Palaeoecology, 30, 157-189. Kellogg. T.B., and D.E. Kellogg. 1981. Pleistocene sediments beneath the Ross Ice Shelf. Nature, 293, 130-133. Kellogg, T.B., and T.S. Truesdale. 1979. Late Quaternary paleoecology and paleoclimatology of the Ross Sea: The diatom record. Marine Micropaleontology, 4, 137-158. Kellogg, T.B., D.E. Kellogg, and T.J. Hughes. 1985. Amundsen Sea sediment coring. Antarctic Journal of the U.S., 20(5), 79-81. McCollum, D.W. 1975. Diatom stratigraphy of the Southern Ocean. Initial Reports of the Deep Sea Drilling Project, Vol. 28 Washington, D.C.: U.S. Government Printing Office. Setty, M.G.A.P., D.E. Kellogg, and T.B. Kellogg. 1984. Preliminary report on diatoms from the Deep Lake terraces, Vestfold Hills, Antarctica. Antarctic Journal of the U.S., 19(5), 88-90. Truesdale, R.S., and T.B. Kellogg. 1979. Ross Sea diatoms: Modern assemblage distributions and their relationship to ecologic, oceanographic, and sedimentary conditions. Marine Micropaleontology, 4, 13-31.
ANTARCTIC JOURNAL
and
Department of Geological Sciences University of Maine Orono, Maine 04469
We summarize here the results of diatom analyses of water, sediment, and sea-ice samples collected during a cruise of the U.S. Coast Guard icebreaker Glacier to the Amundsen Sea in January of 1985 (T. Kellogg, D. Kellogg, and Hughes 1985). This work, described in greater detail by D. Kellogg and T. Kellogg (in preparation) is the first study of modern Amundsen Sea microfossil distributions and will serve as the basis for interpretation of sediment cores in terms of past oceanographic, glacial, and climatic fluctuations (D. Kellogg and T. Kellogg, Antarctic Journal, this issue). Sample locations are shown in a companion paper in this volume (D. Kellogg and T. kellogg, Antarctic Journal, this issue, figure 1). Marine diatoms in sediments. Fifty-seven marine taxa were identified in the core-top samples (42 to the species level), but most of these taxa occur only rarely (1-5 specimens per sample). Species that were present consistently in most samples, often in moderate to high abundance (more than 10 specimens per sample) include: Actinocyclus actinochilus, Chactoceros sp. spores, Eucampia antarctica, Paralia sol, Nitzschia curta, N. kerguelensis, N. vanheurckii, N. obliquecostata, N. sublineata, and Thalassiosira gra-
cilis. Present in lower abundance were various species of the genra Cocconeis and Thalassiosira. All but two of the marine species recorded are extant in modern antarctic waters or occur in Recent antarctic sediments (e.g., Fenner, Schrader, and Wienigk 1976; Truesdale and Kellogg 1979). These species are typical of McCollum's (1975) Thalassiosira lentiginosa (formerly Coscinodiscus lentiginosus) Parital Range Zone. The two exceptions are Denticulopsis hustedtii and Trinacria pileolus, both of which occur as single specimens in DF85-111 and DF85-96, respectively. These species have stratigraphic ranges inthe Miocene (McCollum 1975) to Pliocene (Ciesielski 1983; Burckle personal communication). Their presence in Amundsen Sea core-top samples suggests either reworking or the exposure of older sediment on the sea floor. Reworking is more likely for both samples because they contain the Quaternary species N. curta and the Quaternary/upper Pliocene species A. actinochilus in abundance (D. Kellogg and T. Kellogg 1986b). Nonmarine diatoms in sediments. Nonmarine diatoms are present in most sediment samples, but abundances are generally much lower than those of marine species and usually consist of only one or two specimens of each species. Taxa recorded include Melosira distans, and species of Cyclotella, Diploneis, Navicula, and Tabellaria. The nonmarine species appear to be distributed nearly uniformly throughout the Amundsen Sea core tops, with slightly higher abundances in cores DF85-95 and DF85-99. Our report of nonmarine diatoms in Amundsen Sea sediments is not anomalous. Many of these same species occur, in comparable abundances, in Ross Sea sediments (T. Kellogg and Truesdale 1979; Truesdale and Kellogg 1979; T. Kellogg and D. 1986 REVIEW
Kellogg 1981). These nonmarine species are widespread in lakes and melt ponds throughout the ice-free valleys of southern Victoria Land (D. Kellogg et al. 1980), on the McMurdo Ice Shelf (D. Kellogg and T. Kellogg 1984, in press), and in the Vestfold Hills (Setty, D. Kellogg, and T. Kellogg 1984). Melt pools occurring on antarctic sea ice could also provide a suitable habitat for nonmarine diatoms throughout the circumantarctic sea-ice zone. Introduction of nonmarine diatoms to marine sediments requires only melting of the pack ice. Once they are introduced to the water column, currents may carry diatoms even beneath ice shelves and floating glacier tongues, such as Pine Island Glacier. Diatoms in ice and water samples. Additional material was collected for comparison of fossil and living diatom distributions. Sea-water samples were obtained routinely at each coring station, and ice samples were collected intermittently. All ice analyzed was stained green or red by algal material. Sea water and melted ice were filtered to extract diatoms. Filters (cleared with acetic acid) were mounted on slides using Hyrax. All our ice and water samples contained abundant marine diatoms and were dominated by large to very large numbers of N. cylindrus, Nitzchia curta, N. vanheurckii, and N. obliquecostata, in varying proportions, were subdominants in most samples. These four species together usually comprised over 95 percent of each sample in our quantitative analyses, and a total of 300 specimens was almost always obtained after analyzing only a small portion of each slide. The overwhelming dominance in ice and water samples of N. cylindrus may be attributed to a seasonal bloom, because all these samples were collected within 1 week and because they cover almost the entire north-south extent of the eastern Amundsen Sea. Other species which are known to spend part of their life cycle attached to the underside of the sea ice (e.g., N. curta, N. kerguelensis, and N. vanheurckii are, predictably, subdominants. More than half of the sea-ice and sea-water samples contained occasional specimens of nonmarine diatoms. One sample (DF85-73-55) had nearly 50 specimens of a small delicate species of Navicula which we have not encountered previously but which we suspect is nonmarine, as are most members of that genus. Nonmarine diatoms in sea-ice samples may represent populations that inhabit small melt pools or occur at the base of the snow layer (i.e., in situ assemblages), or they may have been carried from some terrestrial location by winds. The low abundances of nonmarine diatoms in our ice samples (except DF85-73-55) suggest that they represent a contaminant and were probably introduced by winds. Scattered occurrences of nonmarine diatoms in surface water samples probably also result from distribution by winds. We also sampled melt ponds on islands in the Amundsen Sea, to determine if nonmarine species present in this area are similar to those in the Ross Sea sector and elsewhere. Samples were collected from open water in ponds on the Lindsey and Edwards Islands. Both these samples were dominated by the marine species N. cylindrus, although nonmarine species comprised 22.4 percent of the diatom flora at the Lindsey Islands. We suspect that marine species are introduced to these ponds by storm waves and spray, an hypothesis that is supported by the lower percentage of marine species at the higher elevation Lindsey Islands site. Nonmarine diatoms at the Lindsey Islands are dominated by formae of the species Navicula muticopsis, which occur commonly in similar melt ponds in the ice-free valleys of southern Victoria Land and on the McMurdo Ice Shelf (D. Kellogg et al. 1980; D. Kellogg and T. Kellogg in press). The 161
same small delicate Navicula species we noted in the ice sample at DF85-74-55 was also found in both terrestrial ponds samples. We conclude that both these sites are situated too close to the sea to give an accurate representation of a typical nonmarine diatom flora for the area surrounding the Amundsen Sea. We thank Captain W. Hewell and the officers and crew of U.S. Coast Guard icebreaker Glacier, Terence Hughes, and John Anderson and his students, who assisted with our coring project in January 1985. Dennis Cassidy assisted with sampling the cores. David Thompson and Stephanie Staples assisted with sample preparation. This work was supported by National Science Foundation grant DPP 80-20000. References Burckle, L.H. 1985. Personal communication. Ciesielski, P.R 1983. The Neogene and Quaternary diatom biostratigraphy of Subantarctic sediments, Deep Sea Drilling Project Leg 71. Initial Reports of the Deep Sea Drilling Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office. Fenner, J . , H.-J. Schrader, and H. Wienigk. 1976. Diatom phytoplankton studies in the Southern Pacific Ocean, composition and correlation to the Antarctic Convergence and its paleoecological significance. initial Reports of the Deep Sea Drilling Project, Vol. 35. Washington, D.C.: U.S. Government Printing Office. Kellogg, D.E., and T.B. Kellogg. 1984. Diatoms from the McMurdo Ice Shelf, Antarctica. Antarctic Journal of the U.S., 19(5), 76-77. Kellogg, D.E., and T.B. Kellogg. 1986a. Biotic provinces in modern Amundsen Sea sediments: Implications for glacial history. Antarctic Journal of the U.S., 21(5).
162
Kellogg, D.E., and T. B. Kellogg. 1986b. Diatom biostratigraphy of sediment cores from beneath the Ross Ice Shelf. Micropaleontology, 32, 74-94. Kellogg, D.E., and T.B. Kellogg. In preparation. Microfossil distributions in modern Amundsen Sea sediments. Palaeogeography, Palaeoclimatology, Palaeoecology.
Kellogg, D.E., and T.B. Kellogg. In press. Diatoms of the McMurdo Ice Shelf, Antarctica: Implications for sediment and biotic reworking. Palaeogeography, Palaeoclirnatology, Palaeoecology.
Kellogg, D.E., M. Stuiver, T.B. Kellogg, and G.H. Denton. 1980. Nonmarine diatoms from late Wisconsin perched deltas in Taylor Valley, Antarctica. Palaeogeography, Palaeocli,natology, Palaeoecology, 30, 157-189. Kellogg. T.B., and D.E. Kellogg. 1981. Pleistocene sediments beneath the Ross Ice Shelf. Nature, 293, 130-133. Kellogg, T.B., and T.S. Truesdale. 1979. Late Quaternary paleoecology and paleoclimatology of the Ross Sea: The diatom record. Marine Micropaleontology, 4, 137-158. Kellogg, T.B., D.E. Kellogg, and T.J. Hughes. 1985. Amundsen Sea sediment coring. Antarctic Journal of the U.S., 20(5), 79-81. McCollum, D.W. 1975. Diatom stratigraphy of the Southern Ocean. Initial Reports of the Deep Sea Drilling Project, Vol. 28 Washington, D.C.: U.S. Government Printing Office. Setty, M.G.A.P., D.E. Kellogg, and T.B. Kellogg. 1984. Preliminary report on diatoms from the Deep Lake terraces, Vestfold Hills, Antarctica. Antarctic Journal of the U.S., 19(5), 88-90. Truesdale, R.S., and T.B. Kellogg. 1979. Ross Sea diatoms: Modern assemblage distributions and their relationship to ecologic, oceanographic, and sedimentary conditions. Marine Micropaleontology, 4, 13-31.
ANTARCTIC JOURNAL
