Growth of Saccharina latissima (Laminariales, Phaeophyceae) cultivated offshore under exposed conditions

Implementation of open sea seaweed aquaculture has been pursued in Europe for high biomass production to be used for different purposes, including the biorefinery pipeline. Offshore cultivation has been proposed to avoid conflict with other uses of coastal areas such as fishing and recreational activities, and preferably associated with other compatible activities such as wind energy production or fish aquaculture to optimise costs and operation. Saccharina latissima is a European kelp species that finds its southern distribution limit in northern Portugal and is considered a good candidate for commercial cultivation. The present work studied growth performance of this species in exposed conditions, at 5, 10 and 15 m depth from February until September. Photosynthetic performance was also assessed at those depths in summer. Saccharina latissima grew in offshore exposed conditions at the southern distribution limit of the species, with growth rates of 3.3%-4.5% day(-1) between January and May, while withstanding high wave heights. Results indicate that for food applications the growing season in these conditions may be extended until May. If used for applications with less stringent demands for appearance - for example, feed or biofuels - harvest can be delayed further. Optimisation of technology and understanding the underlying biology of S. latissima is needed for cultivation in these conditions. This will include development of low-maintenance/high-resistance support structures and harvest techniques, in addition to strategies for early deployment to improve cultivation reliability and to extend the growth period.