E. von Elert
Limnology, Biochemistry
(Assistant professor)
Univ. Konstanz, Germany
We investigate biochemically mediated processes that are involved in classical topics like
resource competition and predator-prey interactions in plankton organisms. In order to gain
insight into the mechanisms of chemically mediated ineractions we have established smallscale laboratory systems which mimic responses known to occur in lakes. Research
included biochemical interactions among primary producers, among phytoplankton and
grazers and among predators and zooplankton.
Planktonic cyanobacteria release allelochemicals into their environment that inhibit the
growth of other phytoplankton species. The model organism Trichormus doliolum released
allelochemicals under conditions of active growth indicating that the release of such
compounds is a physiological process of healthy cells. The release of the major allelopathic
compound was significantly increased under conditions of phosphorus limited growth
which suggest a coupling of enhanced competition for phosphorus and the release of
allelopathic compounds [1]. The major allelopathic compound proved to be inhibitory over
a broad range of concentrations and interfered with photosystem II - mediated electron
transport, suggesting that the compound is more inhibitory under light-limiting than under
light-saturated conditions [2].
A single-celled culture of the green alga Scenedesmus starts to form cell-colonies
(coenobia) when a chemical cue released by the filter-feeding grazer Daphnia is added. The
formation of cell-colonies is presumably protective for the alga and hence changes the
phytoplankton-zooplankton interface. We have partially chemically characterized the
inducing kairomone [3].
Vertebrate and invertebrate predators chemically induce antipredator responses in Daphnia
thereby influencing the top-down effect on the whole foodweb. The cue released by the
red-midge larvae Chaoborus induces morphological changes in Daphnia pulex. We have
enriched and chemically characterized the kairomone and shown that the polar nature of the
low-molecular-weight compound makes the cue a fast-spreading compound and minimizes
losses due to volatility [4].
A kairomone released by fish induces a diel pattern of vertical migration (DVM) in
Daphnia which reduces losses due to predation. The low-molecular-weight kairomone
(<500 Da) was released regardless of the nutritional status of the fish (hungry/fed) or the
kind of food [5]. Partial chemical characterization of the cue showed no differences of the
kairomones released by Leucaspius delineatus, Carassius carassius and Rutilus rutilus,
which suggests that the cues are chemically very similar if not identical [6]. Hence Daphnia
seems to respond to a kairomone which is rather constitutively released and which is not
specific for the fish species.
Future directions will focus on the zooplankton-phytoplankton interactions. We will look
for biochemical constituents of phytoplankton to explain foodquality for grazing
zooplankton.
Selected publications:
[1] Von Elert, E. & Jüttner, F. Phosphorus limitation not light controls the exudation of
allelopathic compounds by Trichormus doliolum. Limnology and Oceanography (in press).
[2] Von Elert, E. & Jüttner, F. Factors influencing the allelopathic activity of the planktonic
cyanobacterium Trichormus doliolum. Phycologia (in press).
[3] Lampert, W.; Rothhaupt, K.O. & von Elert, E. (1994). Chemical induction of colony
formation in a green alga (Scenedesmus acutus) by grazers (Daphnia). Limnology and
Oceanography 39: 1543-1550.
[4] Tollrian, R. & von Elert, E. (1994). Enrichment and purification of Chaoborus
kairomone from water: Further steps toward ist chemical characterization. Limnology and
Oceanography 39(4): 788-796.
[5] Loose, C.J.; von Elert, E. & Dawidowicz,P. (1993). Chemically induced diel vertical
migration in Daphnia: a new bioassay for kairomones exuded by fish. Archiv für
Hydrobiologie 126: 329-337.
[6] Von Elert, E. & Loose, C.J. (1996). Predator-induced diel vertical migration in
Daphnia: enrichment and preliminary chemical characterization of a kairomone exuded by
fish. Journal of Chemical Ecology 22(5): 885-895.
Workgroup
Aquatic Chemical Ecology
Prof. Dr. Eric von Elert
Research Interests | Current Research Activities | Earlier
Studies | Selected Publications
University of Köln
Zoological Institute
Aquatic Chemical Ecology
Weyertal 119
D-50923 Köln
Germany
Tel: +49 (0)221 470 6084
Fax: +49 (0)221 470 5965
Contact me (replace "at" by "@").
Our workgroup is new at the University of Cologne
since summer 2006. Detailed information on the
Workgroup Aquatic Chemical Ecology will follow
soon.
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Aquatic Chemical Ecology
Köln Ecology
Zoological Institute
Köln Biology
University of Köln
The ecological function of volatile aldehydes (oxylipins) in freshwater benthic
ecosystems
(in cooperation with Prof. F. Jüttner, University of Zürich, Switzerland and PD Dr.
Eric von Elert, University of Konstanz, Germany)
Volatile aldehydes (or oxylipins) released from damaged diatom cells have been
shown to dramatically lower the hatching success of herbivorous copepods and
therefore are considered to form an activated defence strategy of the diatoms versus
herbivores. Alternatively, such substances might also serve as infochemicals,
especially in biofilms of benthic algae and cyanobacteria. In this project, I
investigate the interactions between oxylipins released by benthic diatoms and
herbivorous gastropod grazers.
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Earlier Studies
Food quality and food choice in freshwater gastropods
As biofilm grazers, gastropods have considerable impact on the productivity and
community structure of benthic ecosystems in many limnetic and marine systems.
Compared to other littoral invertebrates, gastropods are relatively large grazers and
therefore able to cause large predation pressure on the biofilm community even at
low densities. In Lake Constance, snails (mostly the genera Radix and Bithynia) are
very abundant and can therefore be considered as one of the key components of the
littoral food web. The project addressed the following main questions:
I.
II.
III.
Do food quality differences of photosynthetic primary producers known
from planktivore grazers like Daphnia, exist also for freshwater gastropods?
What are the biochemical constraints of food quality for these organisms?
Are there food preferences in those freshwater snails?
(Project duration from 2001 continued through 2005/06 - This project is part of the
Collaborative Research Center SFB 454 - "Littoral of Lake Constance", funded by
the Deutsche Forschungsgemeinschaft)
Incucible defences in eucaryotic microalgae
The common green algal genus Scenedesmus shows an extremely high degree of
phenotypic plasticity. In the presence of herbivorous zooplankton, these naturally
unicellular microalgae form colonies that are too large to be ingested by small
herbivores. Thus, this strategy can be considered as an effective inducible defense
for these microalgae. However, the chemical structure of the kairomone, which is
released by the zooplankton and induces the formation of colonies in the algae is not
yet known. In this project, I purified this kairomone from water that had been
incubated with herbivorous zooplankton and experimentally tested further ideas on
the chemical identity and release of this infochemical.
Molecular taxonomy of freshwater microalgae
(in cooperation with Dr. Erik van Hannen, Netherlands Institute for Ecology, and
Dr. Miquel Lürling, Wageningen Agricultural University, The Netherlands)
As mentioned above, the green algal genus Scenedesmus shows high phenotypic
plasticity in response to environmental conditions. Unfortunately, taxonomic
ordering of the Scenedesmaceae has so far been largely dependent only on
morphological characteristics. As a consequence, many morphotypes of strains of
Scenedesmus have been classified as independent species dependent on the
morphology of the cells and colonies. This led to the description of a total of over
1300 species and subspecies in the genus Scenedesmus, of which probably only a
fraction are valid species. In this project, I attempted to resolve the chaotic
taxonomic situation in the Scenedemaceae with the aid of molecular methods. The
ITS2 region of the ribosomal DNA of 34 strains of Scenedesmus was sequenced and
the sequences were aligned based on a secondary structure model of the ITS2-RNA.
This allowed for the distinction between several clusters and supported the current
division of the former genus Scenedesmus into the genera Scenedesmus and
Desmodesmus.
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Selected publications
PhD Thesis: Patrick Fink (2006). Food quality and food choice in freshwater
gastropods: Field and laboratory investigations on a key component of littoral food
webs. Logos Verlag, Berlin 133 pp. ISBN 3-8325-1203-9. Order a copy at the
publisher's website or contact me via e-mail.
peer-reviewed
* Patrick Fink and Eric von Elert (2006). Physiological responses to stoichiometric
constraints: nutrient limitation and compensatory feeding in a freshwater snail.
Oikos 114: in press. DOI: 10.1111/j.2006.0030-1299.14951.x
* Patrick Fink, Eric von Elert and Friedrich Jüttner (2006). Oxylipins from
freshwater diatoms act as attractants for a benthic herbivore. Archiv für
Hydrobiologie 167: in press.
* Patrick Fink, Eric von Elert and Friedrich Jüttner (2006). Volatile foraging
kairomones in the littoral zone: attraction of an herbivorous freshwater gastropod to
algal odors. Journal of Chemical Ecology 32: in press.
* Patrick Fink, Lars Peters and Eric von Elert (2006). Stoichiometric mismatch
between littoral invertebrates and their periphyton food. Archiv für Hydrobiologie
165 (2): 145-165. DOI: 10.1127/0003-9136/2006/0165-0145
* Patrick Fink and Eric von Elert (2006). Food quality of algae and cyanobacteria
for the freshwater gastropod Bithynia tentaculata: the role of polyunsaturated fatty
acids. Verhandlungen der internationalen Vereinigung für theoretische und
angewandte Limnologie 29 (3): 1235-1240.
* Erik J. Van Hannen, Patrick Fink and Miquel Lürling (2002). A revised secondary
structure model for the internal transcribed spacer 2 of the green algae Scenedesmus
and Desmodesmus and its implications for the phylogeny of these algae. European
Journal of Phycology 37 (2): 203-208. DOI: 10.1017/S096702620200361X
conference proceedings (in german)
* Patrick Fink und Eric Von Elert (2006). Das C:N:P-Verhältnis von Periphyton und
seine ökologische Relevanz für herbivore Makroinvertebraten. Tagungsbericht,
Deutsche Gesellschaft für Limnologie (DGL) - Jahrestagung 2005 (Karlsruhe): in
press.
* Patrick Fink und Eric Von Elert (2004). Freisetzung flüchtiger organischer
Verbindungen aus benthischen Süßwasseralgen durch weidende Schnecken.
Tagungsbericht, Deutsche Gesellschaft für Limnologie (DGL) - Jahrestagung 2003
(Köln): 569-573.
* Patrick Fink und Eric Von Elert (2003). Chemosensorische Futterwahl limnischer
Gastropoden. Tagungsbericht, Deutsche Gesellschaft für Limnologie (DGL) Jahrestagung 2002 (Braunschweig): 329-333.
* Patrick Fink und Eric Von Elert (2002). Daphnia-induzierte Coenobienbildung bei
Scenedesmus obliquus - chemische Charakterisierung des Kairomons.
Tagungsbericht, Deutsche Gesellschaft für Limnologie (DGL) - Jahrestagung 2001
(Kiel): 579-584.
Contact me for reprints.
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