The Potential for Upscaling Kelp (Saccharina latissima) Cultivation in Salmon-Driven Integrated Multi-Trophic Aquaculture (IMTA)

Abstract

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.

Latitudinal, seasonal and depth-dependent variation in growth, chemical composition and biofouling of cultivated Saccharina latissima (Phaeophyceae) along the Norwegian coast

“…Growth performance The frond length and biomass yield peaked 5 and 8 weeks later in the northern (9-69°N) than in the central (6-63°N) and southern (1-58°N) locations, respectively, likely because of seasonal differences in temperature, daylight and an earlier depletion of ambient inorganic nutrients by phytoplankton blooms in the low than high latitudes (Rey et al 2007;Ibrahim et al 2014). Maximum frond length and biomass yield were greatest at central (6-63°N, in summer) and northern (9-69°N, in autumn) locations, with levels comparable to S. latissima previously cultivated in Norway (Handå et al 2013;Fossberg et al 2018;Forbord et al 2019;Matsson et al 2019) and as high as or higher than several cultivation trials across Europe under variable conditions (Peteiro et al 2014;Mols-Mortensen et al 2017;Bak et al 2018). The maximum yield of 14 kg m −1 found in our study is far lower than registered for other cultivated kelp species like Macrocystis pyrifera in Chile (up to 22 kg m −1 ) (Macchiavello et al 2010) and hybrids of Undaria pinnatifida and Undariopsis peterseniana in Korea (37.5 kg m −1 ) (Hwang et al 2012) due to both morphology/individual biomass potential and breeding strategies.…”

The Kelp Cultivation Potential in Coastal and Offshore Regions of Norway

“…An individual based growth model for sugar kelp has been developed and coupled with SINMOD (Broch and Slagstad, 2012;Broch et al, 2013;Fossberg et al, 2018). The state variables in the growth model are frond area (A, unit: cm 2 ), internal nitrogen reserves (N, unit: g N (g structural mass) −1 ), and internal carbon reserves (C, unit: g C (g structural mass) −1 ).…”

“…In absence of large, high resolution data sets on industrial cultivation yields, a coupled hydrodynamicbiogeochemical ocean model system (SINMOD;Wassmann et al, 2006) was used. The model has been further coupled with an individual based growth model for S. latissima (Broch et al, 2013;Fossberg et al, 2018). Although dynamical modeling can never replace field experiments and surveys, the simulations provide results resolved in time and space that are especially useful in "data poor" contexts.…”

Performance measures and models for open‐water integrated multi‐trophic aquaculture

“…), and there has recently been some progress on this for macroalgae in IMTA (Fossberg et al . in revision ).…”