Institut für Ostseeforschung Warnemünde
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Dipl.-Biol. Juliane Unger

Vorname Nachname
Address:
Leibniz-Institute for Baltic Sea Research
Seestrasse 15
D-18119 Rostock
Germany
Phone:
+49 381 5197 3416
Fax:
+49 381 5197 440
E-Mail:

Research

Work and studies

  • since 2009: Research assistant/ PhD within the BIOACID I project (BMBF), title: "DOP production and utilization by phyto- and bacterioplankton under elevated CO2 concentrations"
  • 10/2002 - 12/2007: Academic studies in biology at the University of Rostock, diploma thesis: "Expressionsregulation der Glycindecarboxylase"

Long-term stays at other institutions:

  • 9/2010 - 12/2010: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven

BIOACID I

tl_files/staff/unger/images/Logo-Bioacid.gif Subproject 1.2.3: DOM (DOP) availability and phosphorus utilization

Objective: For the research of the DOM (DOP) release by phytoplankton and the DOM (DOP) effects on phosphorus utilization by heterotrophic bacteria different approaches will be used.

  1. Batch experiment (March - May 2010)
    The laboratory experiment was conducted in collaboration with the subprojects 1.2.1, 1.2.2 und 1.2.4 (BIOACID I). The bipartite approach was carried out under the influence of three different CO2 concentrations (low ~300 µatm, medium ~400 µatm, high ~600 µatm). In the first part, growth, production and turnover of C, N, and P have been investigated in a Nodularia spumigena culture. The second part consisted of the Nodularia filtrate where heterotrophic bacteria from the Baltic Sea have been added. The results showed a stimulation of the Nodularia culture under elevated pCO2 (Wannicke et al., 2012) accompanied by a strengthened phosphorus demand (Unger et al., 2012). No significant trends for the heterotrophic bacteria have been observed concerning growth and production even though lower respiration rates at high pCO2 existed.
  2. Chemostat/ batch experiment (Oct. - Dec. 2010)
    The tripartite experiment (chemostat, batch I, and batch II) was again conducted in collaboration with the mentioned subprojects. Aim of this study was to investigate the pCO2 dependency (180 µatm, 380 µatm und 780 µatm) of growth and production by a diatom culture (Thalassiosira weissflogii) and heterotrophic bacteria. T. weissflogii showed a growth optimum at 380 µatm. Bacteria associated with the diatom culture (batch I) showed the highest production rates at the highest primary production. Free living bacteria (North Sea) in the diatom filtrate (batch II) showed no significant trend.
  3. Research cruise with the r/v Elisabeth Mann Borgese (July 2011)
    During the cruise surface water processes in the Baltic Sea along a natural pCO2 gradient have been investigated to draw conclusions from the role of the cyanobacterial summer bloom under rising CO2 concentrations.
  4. Mesocosm experiment (Aug. 2011)
    During the summer cruise (July 2011) 4 mesocosms were refilled with 900 L Baltic Sea water each. Back at the institute the mesocosms were acidified stepwise by sodium bicarbonate and hydrochloric acid to obtain a pCO2 gradient of 180 µatm-natural, 380 µatm, 780 µatm, and 980 µatm. Afterwards, growth and production of the plankton community have been analysed.

Publications

  • Wannicke, N., Endres, S., Engel, A., Grossart, H.-P., Nausch, M., Unger, J., and Voss, M.: Response of Nodularia spumigena to pCO2 - Part 1: Growth, production and nitrogen cycling, Biogeosciences, 9, 2973-2988, doi:10.5194/bg-9-2973-2012, 2012
  • Endres, S., UngerJ., Wannicke, N., Nausch,  M., Voss, M., and Engel, A.: Response of Nodularia spumigena to pCO2 – Part 2: Exudation and extracellular enzyme activities, Biogeosciences Discuss., 9, 5109-5151, doi:10.5194/bgd-9-5109-2012, 2012
  • Unger, J., Endres, S., Wannicke, N., Engel, E., Voss, M., Nausch, G., and Nausch, M.: Response of Nodularia spumigena to pCO2 – Part 3: Turnover of phosphorus compounds, Biogeosciences Discuss., 9, 14709-14750, doi:10.5194/bgd-9-14709-2012, 2012

Talks and poster presentations

  • J. Unger, N. Wannicke, S. Endres, G. Nausch, M. Nausch (2012), Phosphorus transformation by Nodularia spumigena under different pCO2 levels; visiting of the IOW advisory board, Rostock/Warnemuende, February 2012, Poster presentation
  • J. Unger, N. Wannicke, M. Voss, S. Endres, A. Engel, G. Nausch, M. Nausch (2011), Impact of ocean acidification and pCO2 on phytoplankton and bacteria: comparison of two experiments; BIOACID meeting, Bremen, September 2011, talk
  • J. Unger, N. Wannicke, M. Voss, S. Endres, A. Engel, G. Nausch, M. Nausch (2011), Phosphorus transformation by the cyanobacterium Nodularia spumigena under different pCO2 levels; Symposium on Aquatic Microbial Ecology, Rostock/Warnemuende, August 2011, Poster presentation
  • J. Unger, N. Wannicke, S. Endres, G. Nausch, M. Nausch (2011), Phosphorus transformation by Nodularia spumigena and by heterotrophic bacteria under different pCO2 levels; visiting of the IOW advisory board, Rostock/Warnemuende, March 2011, Poster presentation
  • J. Unger, N. Wannicke, S. Endres, G. Nausch, M. Nausch (2010), Phosphorus transformation by Nodularia spumigena and by heterotrophic bacteria under different pCO2 levels - First results; BIOACID meeting, Bremerhaven, September 2010, Poster presentation
  • J. Unger (2009), DOM availability and phosphorus utilization, BIOACID-PhD-Meeting, Bremen, December 2009, talk

Research Cruises

  • July 2011: Elisabeth Mann Borgese (central Baltic Sea)
    Sampling for PhD thesis
  • May 2009: Prof. Albrecht Penck (Baltic Sea monitoring)
    Research assistant for sampling
  • March 2009: Prof. Albrecht Penck (Baltic Sea monitoring)
    Research assistant for sampling