Deposition of Detritus From Near- and Offshore Kelp Farms as a Contribution to CO2 Sequestration Deposition of Detritus From Near- and Offshore Kelp Farms as a Contribution to CO2 Sequestration

There is a surge of interest and activity in macroalgal farming in the Western Hemisphere. Studies ranging from small scale cultivation trials to global theoretical estimates of production potentials mostly agree that the large-scale cultivation potential for macroalgae is great. This invariably leads to questions concerning environmental impacts and ecosystem services provided by this niche of the aquaculture industry. Several ongoing initiatives across all continents are investigating environmental interactions of macroalgal farming, both in terms of negative impacts and ecosystem services. As part of one such initiative financed by the Norwegian Research Council, the potential for horizontal and vertical transport of organic detritus form cultivated kelps is studied. Field work has been performed in order to assess the amount of organic matter being shredded from industrial kelp cultivation sites. The results are used to design cultivation and release scenarios implemented in an ocean model system that was used to simulate the horizontal and vertical transport of kelp farm detritus from several positions near-shore and off-shore the Norwegian coast.

The results indicate, as one would expect, that the transport distance and vertical flux depend on bottom depth, ocean current regimes, season etc. Furthermore, there are several variables/parameters and processes that are important for the simulation results, including sinking speed/density of the particulate matter released, its size distribution etc. Processes such as resuspension and degradation are also of great importance.

The results are discussed in a context of organic enrichment of the pelagic and benthic communities and the potential for sedimentation and positive removal of CO₂ from the upper water column. They are also discussed in a context of the blue carbon contributions from natural kelp forests