Jack R. Hall1, Federico Baltar2, Jonne Kotta1, Christopher D. Hepburn3, Georg Martin1
1 Estonian Marine Institute, University of Tartu, Tallinn, Estonia
2 Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
3 Department of Marine Science, University of Otago, Dunedin, New Zealand
The extracellular release of dissolved organic carbon (DOC) from marine macroalgae supports coastal ecosystem function by supplying photosynthetically fixed carbon to higher trophic orders via the microbial loop. Despite its widely acknowledged biogeochemical importance, DOC production is not typically included in production estimates of coastal systems. Additionally, little is known about how changes in species composition and coverage will affect the supply of DOC to coastal systems. Within the context of the Baltic Sea, anthropogenic forces are driving a decline in habitat forming kelp species (Fucus vesiculosus) which is superseded by filamentous/turfing algal species, a pattern of change observed globally in numerous aquatic systems. In order to evaluate how this change may impact the flow of carbon within Baltic Sea coastal system, the production of DOC by filamentous algae was examined using high temperature catalytic oxidation methodology in order to determine rates of release. In addition, bioassays were used to assess the lability of released DOC by filamentous algae. This data was linked with macroalgae biomass and coverage surveys in order to determine DOC production as metric of algal coverage and used to evaluate how changes in community structure may impact the flow of carbon within the system. Here we discuss how changes in rates of DOC released by filamentous algae relative to F. vesiculosus will act alter carbon flow through the microbial loop. We discuss the impact future filamentous dominated systems will mean for the Baltic Sea in terms of altered carbon flow and how these changes will affect the broader ecology of the system.