Disputation: Johannes C. Rusch
PhD candidate Johannes C. Rusch at the Department of Biosciences will be defending the thesis "Environmental DNA (eDNA) monitoring of two different freshwater host-pathogen complexes in the interface between nature and aquaculture" for the degree of PhD.
Johannes C. Rusch
The disputation will be live streamed using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.
Ex auditorio questions: The chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking "Participants" followed by clicking "Raise hand".
The meeting opens for participation just before 1.15 PM, and closes for new participants approximately 15 minutes after the defense has begun.
Freshwater organisms: how to cope with multiple challenges
Main research findings
Environmental DNA (eDNA) is genetic material obtained directly from environmental samples. Detection of organisms in their environment without observing the biological source is a sensitive, animal-friendly methodology increasingly used to supplement or replace conventional monitoring. However, many knowledge gaps on eDNA dynamics and monitoring potentials, particularly for rare and elusive species and host-pathogen complexes, require further investigation.
This PhD-project focused on two dissimilar host-pathogen complexes of economic importance and species-conservation relevance: Atlantic salmon and the monogenean parasite Gyrodactylus salaris, devastating to indigenous Atlantic salmon, and freshwater crayfish and the crayfish plague pathogen Aphanomyces astaci carried and transmitted by American crayfish but lethal to European crayfish.
Simultaneous eDNA-monitoring of host-pathogen complexes was found advantageous, but detection success differed between target organisms and varied with biological traits, life-cycle events and environmental influences. eDNA-monitoring of crayfish and A. astaci provides information on infection- and population status (presence-absence of native/alien crayfish). Very low population densities and infection levels were detected provided sufficient sampling effort. For Atlantic salmon and G. salaris, fish eDNA is readily detected while the method may fail to detect low parasite intensities due to minute eDNA shedding from G. salaris. The method is nevertheless a useful supplement to work-intensive conventional methods.