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) it was evaluated the impact of different nutrient sources on the relative growth rates (RELATIVE GROWTH RATE) of four different Ulva strains during their adult stage. Previously to this experiment, two experiments were performed to evaluate the of germlings and adults of the four Ulva strains. Because the aim of these experiments was to reproduce the conditions of a large-scale production and a small-scale nursery, the adult material was supplemented with a cheaper commercial fertilizer Blaukorn (COMPO SANA®, Germany) while the germlings (in the nursery set-up) were supplemented with half-strength Provasoli (PES; Provasoli 1968; modifications: HEPES-buffer instead of TRIS, double concentration of Na₂Glycerophosphate; iodine enrichment following Tatewaki, 1966). Therefore, this experiment was performed to guarantee that the use of different nutrient sources would not impact the results of the former experiments. 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 it was cultivated in laboratory conditions in the Alfred Wegener Institute (AWI), Bremerhaven, Germany from that moment on. 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. Fresh thalli from each species and population were placed into 1 L glass beakers and subjected to one of the two treatments: water enriched with commercial fertilizer Blaukorn or with half-strength Provasoli (n = 3). The experiment ran for 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.

We have written confirmation by the Instituto da Conservação da Natureza e das Florestas (ICNF) in its function as ABS National Focal Point as well as Competent National Authority that although Portugal is party to the Nagoya Protocol no national legislation nor any regulatory requirements drawing from the Nagoya Protocol for access to genetic resources in mainland Portugal exist presently. As the samples for this project were collected in mainland Portugal, there are no applicable prior informed consent requirements. The Mediterranean Ulva material was isolated in 1986 (AWI culture number 1262) and in 1967 (AWI culture number 1290). Hence, the samples were taken before the Nagoya Protocol came into force in 2014. Although Regulation EU-No. 511/2014 does not apply accordingly, we complied with our due diligence by asking the Greek National Focal Point about national ABS permit requirements and were granted access with a research permit for flora (RECALL/Δ PΔ/12548/797) issued by the Ministry of The Environment & Energy- Gdd & Dp - Forest Protection Directorate).