the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

More documents

Recommendations

Info

60 6.3 Diatom phytoplankton and phytobenthos analyses Holger Cremer Diatoms or Bacillariophyceae are single-celled algae that produce a pill-box like skeleton composed of biogenic opal (Fig. 6.3-1). These microalgae are very common in all kinds of aquatic environments, freshwater and marine, including extreme habitats like hot sulphur springs and the sea-ice. Diatoms use a wide range of habitats for growth, e.g., the water column, rocks, sand, submerse plants and fish. Fig. 6.3-1: Selection of diatom valves taken with a scanning electron microscope illustrating the morphological variability within the diatoms. A. Complete frustule in girdle view of the genus Coscinodiscus. B-D. Face view of valves of the genera Actinoptychus (B), Tabellaria (C) and Lyrella (D). Photos taken from Round et al. (1990). Diatoms are since long time used in biological and palaeolimnological applications for both the characterization of the ecological state of freshwater habitats and the reconstruction of the climatic and environmental evolution of lakes, respectively (Stoermer & Smol 1999). Arctic environments are characterized by extremes in temperature, radiation, nutrient and habitat availability and ice coverage and do react very sensitively on environmental changes. Consequently, biotas living in these regions, among them the shell-bearing diatoms as the main phytoplankton group have the potential to be a valuable recorder of environmental changes through time (Douglas & Smol 1999). Diatom research in Greenland The diatoms of Greenland and their potential for palaeoenvironmental analyses are insufficiently investigated. While there is a relatively good knowledge of the diatom floras in freshwater environments of West Greenland, the data base in rather poor for East Greenland (see Cremer et al. 2001b, for an extended review of diatom research in Greenland). Even fewer descriptions of diatom floras are available from Northeast Greenland (e.g., Foged 1955, 1989) and are mainly restricted to the description of the taxonomic composition of diatom floras, and offer little palaeoecological information. The same lack of information exists for long sedimentary sequences covering the entire Holocene. The only so far published investigation of a diatombased Holocene history of East Greenland was carried out in lakes of the Scoresby Sund region and on Geographical Society Ø (Cremer et al. 2001a, 2001b).
Working program Sampling of diatom phytoplankton and phytobenthos was carried out in 11 lakes and ponds on Store Koldewey and in one lake on Geographical Society Ø. The taxonomic analyses of the collected diatom floras will give an overview on the taxonomic composition and diversity of epiphytic, epipsammic and epilithic diatom communities in dependence of the hydrology. Phytoplankton communities will be characterized from filtered water samples (Fig. 6.3-2). The physico-chemical characteristics of the water bodies are summarized in the chapter 'Lake hydrology'. Field results A first check of the phytoplankton filter samples revealed that the diversity of pelagic diatom communities in deeper lakes is generally low. The only centric, planktonic diatom genus found on selected filters is Cyclotella which, however, is present in relatively low cell numbers. This is supported by observations of Cremer et al. (2001b), who found Cyclotella as the only present planktonic diatom genus in a long sedimentary sequence from Raffles Sø (Scoresby Sund region, East Greenland) covering the entire Holocene. However, further analyses have to confirm this preliminary observation. Fig. 6.3-2: Typical lake margin environment on Store Koldewey. The lake was partly covered by thin ice. Benthic diatoms are attached to rock and stone surfaces, the soft sediment between the rocks and submerged algae. 61
Page 1:
the Expedition ARKTIS-XIX/4 of the
Page 5 and 6:
1 Cruise summary W. Jokat The exped
Page 8 and 9:
6 1.1 Wetterverlauf ARK XIX/4a Bei
Page 10 and 11:
8 noch vor der Küste, fern davon a
Page 12 and 13: 10 northerly wind increased steadil
Page 14 and 15: 12 In the latest stages of the proj
Page 16 and 17: Profile Date/Time Start Date/Time T
Page 18 and 19: Station Typ Extra Lat Long Höhe [m
Page 20 and 21: Station Typ Extra Lat Long Höhe [m
Page 22 and 23: Date Flight Start Time End Time No
Page 32 and 33: 30 Preliminary results Along profil
Page 34 and 35: 32 In addition to the deep seismic
Page 36 and 37: 34 Fig. 2-5: Flight statistics for
Page 38 and 39: 36 Fig. 3-1: Seafloor topography of
Page 40 and 41: 38 In total, the PARASOUND system o
Page 42 and 43: 40 Figure 4.1-3: Example of PARASOU
Page 44 and 45: 42 Station Latitude Longitude Date
Page 46 and 47: 44 After PCR was finished, samples
Page 48 and 49: 46 Potsdam Lake (Shannon Island) Sc
Page 50 and 51: 48 In den Schmelzwassertümpeln kon
Page 52 and 53: Temp. Sal. Tiefe max. Tiefe Trübe
Page 54 and 55: 52 Store Koldewey Store Koldewey is
Page 56 and 57: 54 In the shallow ponds the hydrolo
Page 58 and 59: 56 The low amounts of solubles in t
Page 60 and 61: 58 lake core no. latitude longitude
Page 64 and 65: 62 Generally, all sampled benthic s
Page 66 and 67: 64 shaped profile at the top were i
Page 68 and 69: 66 depth horizon description sample
Page 70 and 71: 68 measured in the field, and the c
Page 72 and 73: 70 Summary of results The summit pl
Page 74 and 75: 72 Pre-Holocene shell material Pre-
Page 76 and 77: 74 Christensen, T.R. (1993): Methan
Page 78 and 79: 76 No EVK2-2001-00215 (ASOF-N). The
Page 80 and 81: 78 Altimeters Model 2110-2, SN 189
Page 82 and 83: 80 Mooring Latitude Longitude Water
Page 84 and 85: 82 Mooring Latitude Longitude Water
Page 86 and 87: 84 30° W 20° W 30° W Greenland 2
Page 88 and 89: Fig. 7-4: Vertical transects of pot
Page 90 and 91: 88 8 Bericht zur akustischen Vermes
Page 92 and 93: 90 Quality control sheet - Profile
Page 94 and 95: 92 Quality control sheet - Profile
Page 96 and 97: Station List Station Date Time Posi
Page 98 and 99: Station Date Time PositionLat Posit
Page 112 and 113:
Station Date Time PositionLat Posit
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
142 Beteiligte Institutionen / Part
Page 146 and 147:
144 Fahrtteilnehmer / Participants
show all

the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

Create successful ePaper yourself

Delete template?

Save as template?