Doctoral defence: Jack Royd Hall "Dissolved organic carbon dynamics of Baltic Sea macroalgae: production, bioavailability and ecosystem effects"

On 21 February at 14:15 Jack Royd Hall will defend his doctoral thesis "Dissolved organic carbon dynamics of Baltic Sea macroalgae: production, bioavailability and ecosystem effects" for obtaining the degree of Doctor of Philosophy (in Hydrobiology and Fisheries).

Supervisors:

Professor Georg Martin, University of Tartu

Professor Chrstopher David Hepburn, University of Otago (New Zealand)

Opponent:

Research Fellow Maria E. Asplund, University of Gothenburg (Sweden)

Coastal ecosystems are among the most biologically productive areas on Earth, serving as vital hubs for biodiversity and playing a crucial role in global carbon cycling. Within these systems, macroalgae, or seaweeds, are key contributors, transforming inorganic carbon into dissolved organic carbon (DOC) that fuels microbial communities and sustains higher levels of the food web. Despite their importance, the role of macroalgae-derived DOC in the microbial loop and its potential as a significant source of blue carbon remains understudied. At the same time, coastal ecosystems face growing threats from human activities such as nutrient pollution, urban development, and climate change, which are driving shifts in macroalgal community composition. Notably, kelp forests – efficient carbon storers – are being replaced by fast- growing filamentous algae that release carbon more rapidly, disrupting energy transfer to microbial communities and weakening the foundation of the food web. These changes threaten overall ecosystem productivity and resilience, with cascading effects that extend beyond individual species to entire coastal ecosystems and the human communities that rely on them for food security, livelihoods, and natural storm barriers. By investigating the connections between macroalgal DOC dynamics, microbial processes, and ecosystem changes, this thesis enhances our understanding of how coastal systems contribute to the marine carbon pool. These insights are critical for developing conservation strategies that protect the resilience of these ecosystems, ensuring their continued role in supporting biodiversity, regulating carbon cycles, and providing biological services.

The defence will be held J. Liivi 2 - 127 and Zoom: https://ut-ee.zoom.us/j/95790917413?pwd=TpQJqGXxK0DbyHuel9JMivbTaFNkC0.1

(Meeting ID: 957 9091 7413, Passcode: 465116)