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) there was a need to compare artificial and natural seawater based on their nutrient composition and concentration. This experiment was performed to guarantee that the results from the other experiments in this paper were not caused by the different types of water, considering that before the start of these experiment the original cultures were growing in natural seawater. The artificial seawater (30 PSU) (Seequasal-Salz, Seequasal Salz Production and Trade GmbH, Münster, Germany) used in this experiment was made in the laboratory at the Alfred Wegener Institute (AWI), Bremerhaven, Germany, right before being analysed. The natural seawater (30 PSU ± 2 PSU) was collected by the Research Vessel Uthörn in the surrounding area of Helgoland, Germany. The process of collection of natural seawater was made every week to refill and supplement the tanks at AWI, Bremehaven. Therefore, the time of the collection and specific location are not known. The nutrient concentration analysis was done in October 2022 at AWI. Before the analysis both water types were pasteurized for 4 hours at 99 °C. The samples collected for analysis were filtered (0.2 µm) (Nalgene®, Nalge Nunc International, USA) and separated into falcon tubes (n = 3). The analysis was performed by an auto-analyser (SEAL Analytical, United Kingdom) and the concentrations of Phosphate, Ammonium, Nitrite and Nitrate were measured.

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 germlings of different Ulva species and strains were measured to evaluate the impact of different salinity treatments. We hypothesised that, since their early stages, salinity impacts the relative growth rate of the seaweeds and that different strains are adapted to different salinities. With this data it was possible to use salinity as a tool for selecting the strain with the highest and determine the optimal salinity to grow its germlings under a nursery setting to supplement a large-scale production. 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 nursery 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 half-stregth Provasoli (PES; Provasoli 1968; modifications: HEPES-buffer instead of TRIS, double concentration of Na₂glycerophosphate; iodine enrichment following Tatewaki, 1966). Three germlings with similar size from each species and population were placed into multi-well plates and subjected to different salinity treatments (10, 15, 20 and 30 PSU) (n = 3). The germlings were cultivated for 3 weeks. Because of the small size of the germlings, measuring the fresh weight was not possible and, in this experiment, pictures of the germling development were taken every week and the area of the germlings was measured with the software Image J (Rasband 2012). The difference in size was later used to determine their relative growth rate.

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) 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.

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.

Description: Supralittoral and shallow water seaweed communities are particularly exposed to impacts such as climate change and disturbance by humans. Therefore, their classification, the study of composition, and the monitoring of their structural changes are particularly important. A phytosociological survey of the supralittoral and upper sublittoral vegetation of the South West Baltic Sea revealed eight phytobenthos communities with two variants comprising 35 taxa of macrophytes (18 taxa of Chlorophyta, 13 taxa of Rhodophyta and four taxa of Phaeophyceae, Ochrophyta). Five of the eight communities were dominated by Ulvales (Ulva intestinalis, Kornmannia leptoderma, and three Blidingia species), the other three by Fucus vesiculosus. Most Fucus vesiculosus-dominated communities contained U. intestinalis and U. linza as subdominants. Only one of the communities had until now been described as an association ( Ulvetum intestinalis Feldman 1937). The syntaxonomic composition of the investigated vegetation includes both phytocenoses with the domination of green algae ( Ulvetum intestinalis Feldman 1937 and communities of Blidingia marginata, unidentified Blidingia spp. and Kornmannia leptoderma), as well as a number of communities dominated by Fucus vesiculosus. Mainly boreal Atlantic species and cosmopolitans make up the bulk of the species in these associations.

Description: The green seaweed Ulva is a model system to study seaweed–bacteria interactions, but the impact of environmental drivers on the dynamics of these interactions is little understood. In this study, we investigated the stability and variability of the seaweed-associated bacteria across the Atlantic–Baltic Sea salinity gradient. We characterized the bacterial communities of 15 Ulva sensu lato species along 2,000 km of coastline in a total of 481 samples. Our results demonstrate that the Ulva-associated bacterial composition was strongly structured by both salinity and host species (together explaining between 34% and 91% of the variation in the abundance of the different bacterial genera). The largest shift in the bacterial consortia coincided with the horohalinicum (5–8 PSU, known as the transition zone from freshwater to marine conditions). Low-salinity communities especially contained high relative abundances of Luteolibacter, Cyanobium, Pirellula, Lacihabitans and an uncultured Spirosomaceae, whereas high-salinity communities were predominantly enriched in Litorimonas, Leucothrix, Sulfurovum, Algibacter and Dokdonia. We identified a small taxonomic core community (consisting of Paracoccus, Sulfitobacter and an uncultured Rhodobacteraceae), which together contributed to 14% of the reads per sample, on average. Additional core taxa followed a gradient model, as more core taxa were shared between neighbouring salinity ranges than between ranges at opposite ends of the Atlantic–Baltic Sea gradient. Our results contradict earlier statements that Ulva-associated bacterial communities are taxonomically highly variable across individuals and largely stochastically defined. Characteristic bacterial communities associated with distinct salinity regions may therefore facilitate the host's adaptation across the environmental gradient.

Description: In temperate and subarctic regions of the Northern Hemisphere, green algae of the genus Blidingia are a substantial and environment‐shaping component of the upper and mid‐supralittoral zones. However, taxonomic knowledge on these important green algae is still sparse. In the present study, the molecular diversity and distribution of Blidingia species in the German State of Schleswig‐Holstein was examined for the first time, including Baltic Sea and Wadden Sea coasts and the off‐shore island of Helgoland (Heligoland). In total, three entities were delimited by DNA barcoding, and their respective distributions were verified (in decreasing order of abundance: Blidingia marginata, Blidingia cornuta sp. nov. and Blidingia minima). Our molecular data revealed strong taxonomic discrepancies with historical species concepts, which were mainly based on morphological and ontogenetic characters. Using a combination of molecular, morphological and ontogenetic approaches, we were able to disentangle previous mis‐identifications of B. minima and demonstrate that the distribution of B. minima is more restricted than expected within the examined area. Blidingia minima, the type of the genus name Blidingia, is epitypified within this study by material collected at the type locality Helgoland. In contrast with B. minima, B. marginata shows a higher phenotypic plasticity and is more widely distributed in the study area than previously assumed. The third entity, Blidingia cornuta sp. nov., is clearly delimited from other described Blidingia species, due to unique characters in its ontogenetic development and morphology as well as by its tufA and rbcL sequences.