Description: In the paper "Salinity as a tool for strain selection in recirculating land-based production of Ulva spp. from germlings to adults" (Cardoso et al. 2023) the antioxidant activity (AA) experiment aimed to test a previously selected strain, Ulva lacinulata from the NE-Atlantic, and evaluate the variations in AA under different salinity treatments. We hypothesized that by reducing the salinity level in the recirculating land-based system, it would be possible to optimize and increase the quality of the biomass being produced before it being harvested. The NE-Atlantic seaweed was collected in the Óbidos Lagoon, Portugal in January 2021 and was cultivated in laboratory conditions in the Alfred Wegener Institute (AWI), Bremerhaven, Germany. To recreate the conditions of a large-scale system, the strain was grown previously and during the experiment in a medium of artificial seawater (Seequasal-Salz, Seequasal Salz Production and Trade GmbH, Münster, Germany) enriched with a cheaper commercial fertilizer Blaukorn (COMPO SANA®, Germany). Twelve 1 L beakers were filled with artificial seawater at 4 different salinities (10, 15, 20 and 30 PSU), measured with a refractometer (Atago, Japan) (n = 3). Six discs (2 cm) of U. lacinulata were placed in each beaker and, at different times (0 h, 3 h, 24 h, 120 h, 192 h and 240 h) 1 disc was collected from each beaker to evaluate the antioxidant activity. The AA was determined by the ABTS Radical Cation Decolourisation Assay based on Re et al., 1999, and a Trolox standard curve was created by measuring the absorption of different Trolox concentrations in ethanol after being mixed with ABTS. The absorption of the samples at 734 nm was analysed with a microplate reader (Infinite 200 Microplate Reader, Tecan Trading AG, Männedorf, Switzerland) and the AA results obtained were given in Trolox Equivalent (in µg/mL).

Description: In the paper "Salinity as a tool for strain selection in recirculating land-based production of Ulva spp. from germlings to adults" (Cardoso et al. 2023) the relative growth rates of adult thalli of different Ulva species and strains were measured to evaluate the impact of different salinity treatments. We hypothesised that salinity impacts the of the seaweeds and that different strains are adapted to different salinities. With this data we aimed to use salinity as a tool for selecting the strain with the highest and determine the optimal salinity to grow it in the future in a recirculating land-based system. Four strains were tested (U. lacinulata and U. linza from the NE-Atlantic and U. lacinulata and U. flexuosa from the Mediterranean). The NE- Atlantic strains were collected in the Óbidos Lagoon, Portugal in January 2021 and were cultivated in laboratory conditions in the Alfred Wegener Institute (AWI), Bremerhaven, Germany. The Mediterranean strains belong to an AWI collection and were isolated in 1986 and 1987 (U. flexuosa and U. lacinulata, respectively). The cultivation of the Mediterranean species with the purpose of using them for experiments started in June 2021. To recreate the conditions of a large-scale system, the strains were grown previously and during the experiment in a medium of artificial seawater (Seequasal-Salz, Seequasal Salz Production and Trade GmbH, Münster, Germany) enriched with a cheaper commercial fertilizer Blaukorn (COMPO SANA®, Germany). A uniform amount of fresh thalli from each species and population were placed into 1 L glass beakers with salinities of 10, 15, 20 and 30 PSU (each condition n = 3) and cultivated over 3 weeks. The fresh weight was measured once a week by collecting the seaweed and removing the excess water with absorbent paper three times before weighing the samples (Sartorius, Germany). Every time, each sample was measured 3 times. Based on the fresh weight measured each week, it was possible to calculate the of each strain throughout the experiment.