PhD defence
PhD defence by Isabelle Johansson
Isabelle Johansson will defend her PhD thesis “Population Dynamics of Blue Mussels in Subtidal Areas, Longevity, Recruitment, and Productivity, Under Multiple Stressors”.
On Thursday, 29 January 2026, at 13:00, Isabelle Johansson from DTU Aqua will defend her PhD thesis, “Population Dynamics of Blue Mussels in Subtidal Areas, Longevity, Recruitment, and Productivity, Under Multiple Stressors”.
You can follow the defence online in Zoom via this link or in person at DTU Aqua, Øroddevej 80, 7900 Nykøbing Mors.
Isabelle Johansson’s thesis studies the population dynamics of subtidal blue mussel beds in Limfjorden, Denmark, using long-term data and vessel tracking to assess factors shaping mussel bed longevity, recruitment, and productivity. Data from both wild and on-bottom cultivated beds are analysed to evaluate ecological, management, and economic dimensions of mussel sustainability.
Isabelle Johansson’s results show that older, multi-cohort mussel beds are more stable, whereas half of the new beds disappear within a year, mainly due to predation, fishing, temperature fluctuations, and oxygen depletion. Recruitment is identified as the main driver of population structure, and shell material promotes settlement. The PhD study also compares different cultivation methods and shows that on-bottom cultivation is economically viable under certain conditions.
Blue mussels are key to coastal ecosystems, providing habitat, improving water clarity, supporting nutrient cycling, and serving as a sustainable food source. Despite this importance, wild populations and aquaculture have declined across Europe.
Examiners
- Professor Marja Koski, DTU Aqua (chair)
- Senior Researcher Jacob Capelle, Wageningen University, The Netherlands
- Research Scientist Antonio Agüera, Institute of Marine Research, Norway
Chair of defence
- Senior Researcher Mette Møller Nielsen, DTU Aqua
Supervisors
- Principal Supervisor: Senior Researcher Pernille Nielsen, DTU Aqua
- Co-supervisor: Senior Researcher Camille Saurel, DTU Aqua
- Co-supervisor: Researcher Daniel Taylor, DTU Aqua
Learn more
A copy of the thesis is available for reading at DTU Aqua. Please contact PhD Coordinator Susan Zumbach Johannesen, szjo@aqua.dtu.dk