Our last blog introduces Ulva as one of the current species that we are testing in the lagoon in Venice. But how we can farm this algae? There are two different techniques that can be used effectively for open sea cultivation. One technique that can be used in deeper locations consists of a floating structure, with buoys and ropes that are supported by anchors which have the macroalgae attached. The other technique incorporates a net system that enables the macroalgae to grow in a more controlled setting - this is more favourable for closer-to-shore cultivation.
Cultivation Infrastructure Option #1
Ulva is grown using a free-floating structure referred to as a “germling cluster” (Hiraoka & Oka, 2008).
An example of an Ulva sea farm includes the use of ropes, which are placed slightly beneath the water surface at 1-1.50m, and supporting buoys that are placed every 10m apart. In addition, weights and anchors are required to stabilize the farm's infrastructure.
An example of a floating Ulva macroalgae farm can be seen in the figure shown below (Steinhagen et al., 2021).
Offshore seaweed farm with free-floating structure
Cultivation Infrastructure Option #2
Ulva can also be grown using a net cultivation system. In this method, nets are seeded “artificially” under controlled conditions. This allows for all conditions to be set and monitored throughout the seeding process, and produces higher seedling densities. This in turn can lead to higher biomass production. Nets can then be placed into open ocean or water in a closed environment (i.e tank) on-shore.
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