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Patrick Lorenz

Patrick Lorenz


LMU München/Department Biology II
Aquatic Ecology
Großhaderner Str. 2
82152 Planegg-Martinsried

Room: B02.022
Phone: +49 89 2180 74-213

Research interests

Experimental ecology in lake ecosystems
Nutrient cycles in freshwater lakes
Food web interactions: phytoplankton - zooplankton – fish
Growth and growth conditions of coregonids in Upper Bavarian lakes


Influence of nitrogen deposition on organisms and trophic interactions in the pelagic zone of lake ecosystems.

Anthropogenic induced alterations of the global nitrogen (N) cycle lead to increased N depositions in freshwater lakes. Significantly altered nutrient conditions, with shifts in the prevailing N : phosphorus (P) ratios towards increasing N : P ratios, are accompanying consequences for the majority of lakes. Increasing ratios of N : P in lake waters potentially influence phytoplankton growth (algal growth) and thus primary production of biomass in lake ecosystems. Shifts in the chemical composition of phytoplankton, and in its nutritional quality as a food source for zooplankton, are to be expected.

The aim of my study is to reveal potential consequences of increased atmospheric N depositions for aquatic organisms of different trophic levels. My focus is particularly on growth and taxonomical composition of phyto- and zooplankton, as well as on the growth of planktivorous fish. A special interest lies on the local whitefish species (Coregonus spec.) of Bavaria. To investigate responses of these organisms to increasing N : P ratios I conduct mesocosm experiments where phytoplankton, zooplankton and juvenile whitefish are exposed to different N gradients with different nitrate (NO3-) : ammonium (NH4+) ratios. Examined parameters are mainly those of water chemistry, chemical composition of phytoplankton (seston stoichiometry) and the taxonomical composition of zooplankton communities. Growth and nutritional conditions of zooplankton and fish are examined by applying RNA : DNA ratio analysis. Additionally, I conduct laboratory experiments to evaluate NH4+ toxicity for zooplankton (cladocerans).

These experimental results are used for estimating the impacts of increasing N : P ratios on the developments of coregonid stocks in Bavarian lakes. Research project: The importance of prevailing nitrogen to phosphorus ratios in Bavarian lakes for the growth of whitefish (NitroFlex)


  • Since 01.01.2014 PhD student, Aquatic Ecology (Herwig Stibor), Ludwig-Maximilians-Universität München (LMU)
  • 2011 – 2013 Master studies in biology (Master of Science), Ludwig-Maximilians-Universität München (LMU)
  • 2008 – 2011 Bachelor studies in biology (Bachelor of Science), Ludwig-Maximilians-Universität München (LMU)


In preparation
P. Lorenz, G. Trommer, Anna Hofmeister, H. Stibor, (in preparation). Ammonium exposure of Daphnia haylina induces life history shifts similar to fish kairomones.

P. Lorenz, G. Trommer, H. Stibor, (submitted). Increasing nitrogen:phosphorus ratios influence zooplankton community compositions and whitefish (Coregonus macrophthalmus) growth in a pre-alpine lake.

G. Trommer, M. Poxleiter, P. Lorenz, E. Bitzilekis, A. Gogaladze, S. Schultes and H. Stibor, (2017). Altered food-web dynamics under increased nitrogen load in phosphorus deficient lakes. Aquatic Sciences. doi: 10.1007/s00027-017-0551-2

M. Poxleitner, G. Trommer, P. Lorenz and H. Stibor (2016) Effects of increased atmospheric nitrogen load on phytoplankton in a phosphorus limited lake. Freshwater Biology. doi: 10.1111/fwb.12821


  • Master Thesis: Lorenz, P. (2013), Influence of atmospheric nitrogen input on plankton communities in a phosphorus limited lake ecosystem. Aquatic Ecology (Herwig Stibor), Ludwig-Maximilians-University Munich, LMU.
  • Bachelor Thesis: Lorenz, P. (2011), Fledermausvorkommen in Landkreis Roth. Neurobiology (Andreas Zahn), Ludwig-Maximilians-University Munich, LMU.

Conference contributions

  • Patrick Lorenz, Gabriele Trommer, Anna Hofmeister, Herwig Stibor (2017), Ammonium exposure of Daphnia (Daphnia hyalina) induces similar life history shifts as fish kairomones. Deutsche Gesellschaft für Limnologie (DGL), Cottbus, Deutschland.
  • Gabriele Trommer, Patrick Lorenz, Ameli Lentz, Herwig Stibor (2016), Nitrogen supply in lakes leads to changing fatty acid composition of phytoplankton and negatively affects zooplankton. International Society of Limnology Austria (SIL Austria) - Deutsche Gesellschaft für Limnologie (DGL), Wien, Österreich.
  • P. Lorenz, G. Trommer, H. Stibor (2015), Increased atmospheric N-deposition can lead to shifts in zooplankton densities in P-limited lakes. Fresh Blood for Fresh Water (FBFW), Mondsee, Österreich.
  • P. Lorenz, G. Trommer, H. Stibor (2015), Influences of N-deposition on a food web of a P-limited lake. Association for the Sciences of Limnology and Oceanography (ASLO), Granada, Spanien.
  • P. Lorenz, G. Trommer, H. Stibor (2014), Increased N-input alters zooplankton densities in P-limited lakes. Deutsche Gesellschaft für Limnologie (DGL), Magdeburg, Deutschland.
  • G. Trommer, M. Poxleitner, E. Bitzilekis, A. Gogaladze, P. Lorenz, H. Stibor (2014), Nitrogen deposition on phosphorus limited lakes: Effects of increasing phosphorus limitation. International Society of Limnology Austria (SIL Austria), Lunz, Österreich.
  • G. Trommer, M. Poxleitner, E. Bitzilekis, A. Gogaladze, P. Lorenz, H. Stibor (2013), Einfluss von erhöhter Stickstoffzufuhr auf Seeökosysteme- ein experimenteller Ansatz. Deutsche Gesellschaft für Limnologie (DGL), Potsdam, Deutschland.