Work Package 7 (Gerlach, Schupp, Dittmar)

"Following migration of animals in the North Sea by environmental DNA (eDNA)"

Broader background of the proposed research project

DOM can act as olfactory cues potentially influencing migration behavior of marine species. While laboratory tests have shown olfactory preferences for specific cues, very little is known whether and how species are responding to DOM in their natural habitat and ecosystem. To test this, we will establish a new detection method of animals in the marine environment and correlate the presence of species with presence or absence of specific DOM. For detecting species we will develop an eDNA method. Free DNA molecules are ubiquitous, released from skin, mucous, urine eggs etc. and are collectively referred to as eDNA (Bohmann et al. 2014). Extraction and identification of waterborne potentially degraded environmental DNA (eDNA) originating from many different organisms, has proven noteworthy in detecting the presence of species. While eDNA can persist in sediments for centuries or millennia, waterborne eDNA may degrade much faster within short time spans (2 weeks) (Thomsen et al. 2011). Studies have shown eDNA concentration to be directly related to number of individuals in mesocosms and natural ponds, but several issues still need to be addressed to validate this method in the marine environment. The implementation of so-called ecosystem-based approaches (Foote et al. 2012) will take a more holistic view than single species studies.

Outline for the proposed PhD research project

The project aims to determine waterborne environmental DNA (eDNA) of migrating species in the North Sea to test for any correlation of their appearance and presence of specific DOM compounds which can serve as chemical attractants. In our project we aim to establish a genetically based detection method to monitor the occurrence of species close to a source of chemical attractants. We will first focus on crustaceans species such as the invading crab Hemigrapsus takanoi and the native crab Carcinus maenas; develop species specific primers that amplify a fragment of the CO1 gene. Chemical attractants which will be identified under laboratory conditions beforehand will be released by chemical source devices. By taking water samples and by eDNA analysis we will determine the presence and attraction of responding species even when we do not see – or do not catch them.

At the beginning, the Ph.D. student will test for the specificity of primers to detect mtDNA CO1 fragments of single individuals and of groups consisting of single and mixed species. He/she will verify qualitatively and quantitatively the detection of species eDNA. Once established, we will take and analyze water samples for eDNA in different distances to the chemical source device in the North Sea to determine the density of species. This project will be conducted in close collaboration with Dittmar (WP 4) to assess the attraction of species responding to chemical signals in the wild. We will also closely collaborate with WP 6 where a different model system is investigated in a similar context.