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Seagriculture 2019

8th International Seaweed Conference

"Seaweed Success Stories"

25-26 September 2019, Ostend, Belgium

Annette Bruhn

Senior researcher, Aarhus University, DK

``Ecosystem impact of large-scale macroalgae cultivation``



Annette Bruhn works as a senior researcher in applied phycology at Department of Bioscience, Aarhus University. Her group leads and participated in several national and international projects on production, optimization and utilization of macroalgae biomass. AB is one of the co-founders of AlgaeCenter Denmark (2010). The mission of Algecenter Denmark is to strengthen science-industrial co-operation towards sustainable and innovative macroalgae production and applications.wick.


Macroalgae production is increasingly viewed as a potential instrument for accelerating ecosystem recovery from coastal eutrophication, as well as for climate mitigation. However, since the impacts on the marine environment of large-scale macroalgae cultivation are relatively undocumented, national authorities in Europe are reluctant in giving cultivation licences for production in larger scale and for periods longer than 5 years. This study aims to document the impact of large-scale kelp (Saccharina latissima) cultivation on physical, chemical and biological aspects of the marine environment.

During a one-week intensive scientific cruise on-board the research vessel AURORA in early summer 2018, a thorough investigation of the marine environment surrounding a Danish 100 hectares kelp cultivation site was carried out. In-situ parameters investigated were: Physical (hydrodynamics, light, temperature), chemical (salinity, nutrient concentrations and fluxes, pH, alkalinity, cDOM, TOC, POM) and biological (pelagic chlorophyll a concentrations, macroalgae standing stock, biofouling, eDNA, benthic fauna) parameters. On-board the research vessel, 24-hour mesocosm studies were performed, investigating in closed systems the dynamics of photosynthesis, respiration, nutrient exchange, and emission of climate gasses of young (one-year) and older (four-year) S. latissima. 

The cruise was successful in collecting data as planned during the pre-harvest period with maximal biomass standing stock. The results of the cruise will be presented and discussed in the context of macroalgae production strategies, future research focus and marine ecosystem management.