Upscaling cultivation of Saccharina latissima on net or line systems; comparing biomass yields and nutrient extraction potentials

Abstract

Production of sugar kelp, Saccharina latissima, has the potential of extracting nutrients and carbon from the seawater and returning it to land as a bioresource. The production thereby acts as an emission capture and utilization instrument contributing to mitigation of eutrophication and climate change. To achieve higher biomass yields improving the effects on climate and environment, and the economic feasibility of the production, cultivation techniques need to be optimized. In Denmark so far, S. latissima production yields have been lower than yields documented from Norway and the Faroe Islands. Use of alternative cultivation infrastructure designs with a higher line density per area, and better understanding the effects of annual and seasonal variations in abiotic parameters on growth, could lead the way towards a future higher yield of the S. latissima production. In this study, S. latissima was cultivated in a Danish commercial scale cultivation site for two consecutive seasons comparing the yields of different cultivation techniques: cultivation on nets and a multi-layer single line system, while also testing the possibility of coppicing the blades instead of applying a full harvest. Biomass yields of 5.0 - 6.8 kg FW m-1 cultivation line year-1, and 10.9 – 30.4 kg FW m-2 net structure were achieved. Biomass production, nutrient and carbon extraction potentials up to 91.3 t FW, 110 kg N, 13.1 kg P and 5.1 t C ha-1 were obtained using net cultivation systems and a 1.5 years growth period. Depth of cultivation had a significant effect on yield, but no effect on dry matter, C, N or P contents of S. latissima in a multi-layered line system. Biomass yields from the same system and site varied with a factor of four between years. The use of coppicing enabled multiple harvests of S. latissima, providing however biomass of reduced quality in the second year. This study demonstrates that the production yield of S. latissima can be increased by optimizing cultivation infrastructure, and indicates that net systems, or other cultivation systems with a high line density in the upper water column, can be a means to increase the areal yield of S. latissima.

A new nursery approach enhances at-sea performance in the kelp Lessonia corrugata

“…After a successful nursery stage, the timing of outplanting (season) is the crucial next step for efficient kelp aquaculture (Peteiro and Freire 2012;Hurd et al 2014a;Peteiro et al 2016;Boderskov et al 2023). This study found a seasonal influence on the development of L. corrugata at sea.…”

“…Understanding the best season (time) for out-planting is also critical for optimising seaweed production but can be challenging since most abiotic and biotic variables that can impact cultivation outcomes vary spatially and temporally (Hurd et al 2014b;Roleda and Hurd 2019;Boderskov et al 2023). Depending on the location, nutrient concentrations, light penetration, seawater temperature, and water motion can vary dramatically between seasons and depths (Brown et al 1997;Ganesan et al 2006;Handå et al 2013).…”

Multi-use of offshore wind farms with low-trophic aquaculture can help achieve global sustainability goals

“…The model assumes that if salinity is optimal, the optimal biomass potential can be reached 99 . Therefore, the model output might overestimate the production potential in areas where nutrients, temperature, light, or a combination of these are limiting growth 100 .…”

A baseline studies programme for sustainable and resilient seaweed cultivation in Faroese fjords

“…They assess that pathogens known from the Asian species Saccharina japonica could be of risk for its close relative, S. latissima, which is widely cultivated in the Nordic countries, including Denmark, the Faroe Islands, Greenland, Norway, and Sweden (Broch et al, 2019;Visch et al, 2020;Wegeberg, Geertz-Hansen and Mols-Mortensen, 2021;Boderskov, Rasmussen and Bruhn, 2023;ICES, 2023).…”