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Kelp cultivation started in Japan, China and Korea, mainly for human consumption; new applications are still expanding. In Chile, three "wild" Lessonia species and Macrocystis pyrifera are under a strong and increasing pressure of exploitation mainly for alginate production and as a source of feed for abalone. Regulatory restrictions for kelp exploitation and the increased demand for biomass provided a positive environment for the installation of a kelp farming industry. Pilot-production studies demonstrated that 200 tonnes (fresh)/ha/year can be achieved and genetic diversity and breeding studies suggested that this volume could be increased. Kelp disease research is a necessary condition for securing the future development of this industry, as are environmental studies on the impacts of large-scale aquaculture. Beyond the positive bioremediation, ecosystem service effects that kelp farming can provide, especially in a region such as in southern Chile, where intensive salmon and mussel cultivation occurs. Life Cycle Assessment suggests that the energy returns on investment in kelp farming are positive, but more detailed data are still required.

Integrated multi-trophic aquaculture (IMTA) has the potential of reducing open-cage fish farming impacts on the environment while also introducing new value chains. The aim of this study was to investigate the growth and composition of the kelp Saccharina latissima in salmon-driven IMTA, and to assess the spatial extent of the influence of salmon derived nitrogen in order to evaluate the upscaling potential for IMTA. S. latissima was cultivated 100, 200, and 1,000 m east and 1,000 m west of a 5,000 tons salmon farm in Western Norway from February to September 2013. The proportion of salmon derived nitrogen available for the kelp showed a clear decline with distance from the farm. Accordingly, the kelp cultivated near the salmon cages grew faster during the spring season, and growth rate decreased with increasing distance from the farm. A spatially explicit numerical model system (SINMOD), including compartments for dissolved nutrients and kelp growth, was tuned to the field data and used to investigate the potential for upscaling IMTA production. The model was used to introduce a new metric—the impacted area IA—for the areal effects of IMTA in terms of the increase in production by IMTA. The model showed that a 25 hectare kelp farm in the vicinity of the studied salmon farm could take up 1.6 of the 13.5 tons of dissolved inorganic nitrogen released during kelp cultivation, amounting to almost 12% of the ammonia released during the cultivation period from February to June. The 25 hectare kelp farm would have a production yield of 1,125 tons fresh weight (FW), being 60% more than that of a non-IMTA kelp farm, while a 20% increase of kelp FW could be obtained over a 110 hectar area in salmon-driven IMTA. To achieve an even mass balance, an area of approximately 220 ha−1 would be needed to cultivate enough kelp to fix an equivalent of the nitrogen released by the fish.

The chemical profile of biorefined Saccharina latissima, Ascophylum nodosum and Palmaria palmata after carbohydrate and polyphenol extraction was analysed with the aim to evaluate the nutritional aspects of biorefined seaweeds as a novel animal feed supplement. Optimised enzymatic saccharification has been used to show that the protein concentration in the residue of Palmaria palmata and Ascophylum nodosum can be increased by more than two fold. Nutritional value of the residue was further enhanced through an increase in total amino acids and fatty acids. As a consequence of removal of inorganic elements such as sodium, potassium and chloride, the total solid and ash content of all three seaweeds was reduced by around 40%. In contrast, divalent metals such as iron and zinc, as well as silicon accumulated in all three residues. Potentially harmful components such as arsenic and iodine were reduced only in brown biorefined seaweeds, whilst in biorefined P. palmata iodine increased by 39% compared to a 24% decline of arsenic. Polyphenol removal in all three seaweeds was >80% and, in combination with enzymatic saccharification, enhanced protein recovery in A. nodosum. This highlights the potential of biorefinery concepts to generate multiple products from seaweed such as extracts enriched in polyphenols and carbohydrates and residue with higher protein and lipid content. 

Guidelines for the introduction of Seaweed Farming asan alternative livelihood opportunity in the coastal zone

The management of the coastal zones of the western Indian Ocean (WIO) is seriously compromised by the over-exploitation of coastal fisheries stocks. This overexploitation is largely due to the over-development of artisanalfisheries, which are particularly difficult to manage.

In fact, there are really only two ways to address this problem: 1) bysimply legislating to reduce the fishing effortsand then enforcing that legislation, which is politically very difficult, or 2) by linking the mutually agreed introduction of less punitivemanagement measures (for example, gear restrictions or closed areas or seasons) with the creation of alternative livelihood opportunities for fishers.

Marine aquaculture is a one such alternative that is increasingly popular following a number of successful introductions in the region. One example is the development of seaweed farming, which has been promoted over the last 20-years but other types of marine aquaculture also have potential as alternative livelihoods. These include the culture of prawns, fish, bivalves, crabs and sea cucumbers.