Alexandrium pseudogonyaulax on copepods
Background The harmful mixotrophic dinoflagellate Alexandrium pseudogonyaulax has been unseen in Northern-European Waters until approximately 15 years ago. Since then, this algae has been increasingly appearing and has been a dominant member of the annually occurring dinoflagellate blooms in late summer. A. pseudogonyaulax is producing the phycotoxins goniodomins belonging to a class of macrocyclic secondary polyketides. Goniodomins have been shown to act cytotoxic presumably through disturbing the actomyosin ATPase activity and the F-actin meshwork. However, apart from goniodomins this algae is also producing lytic substances that have not been structurally elucidated yet and it is mostly unknown whether toxins or lytic substances are responsible for observed adverse effects on other marine organisms. A. pseudogonyaulax seems to be remarkably resistant towards grazing pressure of predators, which may have lead to the unchallenged expansion of this organism.
Research questions: It has already been shown that the presence of copepods feeding on A. pseudogonyaulax leads to a toxin induction in A. pseudogonyaulax. Based on that observation the first research question would be: Does the toxin production of A. pseudogonyaulax also get induced when copepods are feeding on other closely related dinoflagellates? Furthermore, previously generated data hints towards selective feeding abilities of copepods and thus the capability to reject toxic prey. Selective feeding will be investigated with mixed algae cultures in which one algae is stained with a fluorescence dye. Based on that the 2nd research question would be: Do copepods selectively reject A. pseudogonyaulax in the presence of non- toxic food alternatives?
Tasks Apart from toxins and lytic substances, it has been shown that A. pseudogonyaulax is producing transparent exopolymer particles (TEP) and mucus, which is utilized as part of mixotrophic feeding strategy. It is, however, unknown which parameters influence and potentially induce mucus formation. Parameters that would be investigated include different nutrient scenarios and the presence of grazers. This question would be investigated by the establishment of an alcian blue staining protocol, followed by photometric quantification of produced TEP.
This study would involve the handling and maintenance of various algae (heterotrophic, phototrophic, mixotrophic) and zooplankton (copepods) cell cultures. In addition, goniodomins would be extracted from algae cell cultures and subsequently quantified via mass spectrometry (LC-MS/MS). Other analytical techniques would include conventional microscopy techniques and fluorescence microscopy. At the end of the thesis the generated data would be analysed using conventional statistical data analysis techniques in the programming language R. Furthermore, there may be the possibility to join a scientific expedition in the Baltic Sea in August/September on the Baltic Sea, which would focus on HAB species and their associated toxins.
The place of employment will be Bremerhaven, 27570.
Start: as soon as possible
You are interested? Then please send us your application with Cover letter and CV (with all documents merged into one PDF file) by e-mail to: Dr. Bernd Krock ([email protected])
For further information please contact Kristof Möller ([email protected], +49(471)4831-2055).