Band 67, Heft 2 - Special issue: Phylogeny and Ecology of Ulva. Part I; Issue editors: Sophie Steinhagen, Thomas Wichard and Jonas Blomme

During the cultivation of Ulva fenestrata in a land-based aquaculture system, the colonisation of the water tanks’ surfaces and eventually the macroalgal biomass by the biofouling diatom Fragilariopsis oceanica compromises the production process. Since germanium dioxide (GeO 2 ) is an effective growth inhibitor of diatoms, this study aimed to understand how it affects the presence of F. oceanica and the photosynthesis and growth of U. fenestrata as a primary parameter contribution to the biomass production. A toxicological dose-response experiment showed that the diatom’s growth was inhibited at the low GeO 2 concentration of 0.014 mg l −1 . In contrast, the photosynthetic performances and growth rates of U. fenestrata remained unaffected under a wide GeO 2 concentration range (0.022–2.235 mg l −1 ) in small- and large-scale experiments in 1-l glass beakers and 100-l Plexiglass water tanks, respectively. In the latter, the diatom density in the tanks was reduced by 40 %. The costs arising from the use of GeO 2 can range between €2.35 and €8.35  kg −1 fresh weight of produced U. fenestrata biomass under growth conditions resulting in growth rates of 20 and 11.5 % d −1 , respectively. GeO 2 is an effective agent to control biofouling diatoms such as F. oceanica during the land-based biomass production of U. fenestrata .

The use of high-value fatty acids (FA), omega-3 ( n -3), and omega-6 ( n -6) from seaweed could relieve the pressure from natural wild fish sources and reduce overfishing worldwide. This research is designed to explore how the harvest season (winter, spring, and summer) and culture period influence the biomass production yield, lipid content, and FA composition in the green seaweed Ulva sp. The studied seaweed was grown in plastic sleeves with flowthrough seawater in Mikhmoret (East Mediterranean, Israel) from July 2019 to December 2020. The Ulva species was identified as Ulva lactuca Linnaeus by DNA barcoding using rbc L, ITS, and tuf A markers. No detectable genetic variability in U. lactuca samples was found throughout the research period. A quantitative examination of the lipid and FA content in U. lactuca in different harvest seasons revealed that the maximum content of lipids was in the summer, and that of polyunsaturated fatty acids (PUFAs) was in the winter. The PUFA profile included eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, n -3, and n -6, where the n -6/ n -3 ratio was comparable with the desired range for a balanced nutritional diet.

Several studies have shown that endophytic fungal metabolites possess vital biological activities; nevertheless, there is a lack of knowledge regarding the medicinally important marine endophytic fungi associated with the seaweeds mainly found in the Bay of Bengal, Bangladesh. In this study, six endophytic fungi, belonging to five genera and four classes, were isolated from the well-known chlorophyte, Ulva sp. and were most closely related to Chaetomium globosum , Nigrospora magnoliae , Curvularia sp., Curvularia moringae , Aspergillus terreus and Collariella sp. This is the first report of these fungi as endophytes associated with Ulva sp. from the Bay of Bengal, Bangladesh. A preliminary biological evaluation of the ethyl acetate extract of each endophytic fungal crude extract was the prime objective of this research, e.g., antimicrobial assay, 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity and brine shrimp lethality bioassay. Evaluation of test results revealed that each fungal crude extract possessed one or more relevant biological activities. Preliminary chemical screening using TLC and NMR spectroscopic analysis revealed the presence of several secondary metabolites in the crude fungal extracts. These findings suggest that the marine endophytic fungus may be a valuable source for investigating potentially bioactive chemicals or leads for novel drug candidates.

Axenic cultures of the green seaweed Ulva mutabilis were inoculated with bacteria providing essential algal growth and morphogenesis-promoting factors (AGMPFs) and were exposed to temperature shifts from 18 °C to 30 °C. The temperature-dependent effect of bacteria on longitudinal algal growth and the molecular composition of the chemosphere in the algal culture medium was explored. The reductionist tripartite model system of U. mutabilis , Roseovarius sp. MS2, and Maribacter sp. MS6 was applied as a reference and has been changed by substituting Roseovarius with isolates that phenocopy this strain. Rathayibacter festucae IH2 and Roseovarius aestuarii G8 boosted growth at 18 °C but slowed it down at 30 °C. Additional inoculation of Roseovarius sp. MS2 mitigated these adverse bacterial effects partially. At 30 °C, the molecular profile of the chemosphere differed dramatically between all tested tripartite communities, indicating different traits of the same bacterium with changing temperatures. Functional examinations should, therefore, accompany microbiome analysis to detect changing traits with the same microbiome composition.

Species classified in the genus Ulva are important foundational marine primary producers distributed worldwide. These species are particularly abundant and diverse through the northwest Pacific (NWP) where they experience marked latitudinal gradients of environmental heterogeneity. It is unclear, however, to what extent such dynamic conditions can modulate phenotypic and genetic patterns in these organisms, potentially reflecting the influence of historical and contemporary biotic and abiotic factors. Here, we assessed inter- and intra-specific genetic patterns of Ulva species through the NWP using plastid rbc L and tuf A gene sequences. Although we initially targeted Ulva australis based on morphological identification, we recovered eight Ulva genetic entities masked by morphological similarities. Except for the Ulva linza–procera–prolifera and U. lactuca–reticulata complexes, six of these genetic entities were recovered as individual species (i.e.,  U. australis , U. ohnoi , U. californica , U. compressa , U. lacinulata , and U. arasakii ), and showed biogeographic patterns likely explained by clines in sea surface temperature and ocean current dispersal. At intra-specific level, all the genetic entities showed low genetic variation and divergence based on rbc L (0–0.3 %) and tuf A (0–0.9 %) data. Our results provide insights regarding intra- and inter-specific genetic patterns characterizing morphologically similar Ulva species through the NWP. However, further studies are needed to understand the mechanisms underpinning such patterns and the associated ecological and evolutionary implications.

DNA sequences were obtained from 32 blade-forming Ulva specimens collected in 2018 and 2019 from four islands in the Galápagos Archipelago: Fernandina, Floreana, Isabela and San Cristóbal. The loci sequenced were nuclear encoded ITS and plastid encoded rbc L and tuf A, all recognized as barcode markers for green algae. Four species were found, Ulva adhaerens , U. lactuca , U. ohnoi and U. tanneri , all of which have had their type specimens sequenced, ensuring the correct application of these names. Only one of these, U. lactuca , was reported historically from the archipelago. Ulva adhaerens was the species most commonly collected and widely distributed, occurring on all four islands. Previously known only from Japan and Korea, this is the first report of U. adhaerens from the southeast Pacific Ocean. Ulva ohnoi was collected on three islands, Isabela, Floreana, and San Cristóbal, and U. lactuca only on the last two. Ulva tanneri is a diminutive, 1–2 cm tall, high intertidal species that is easily overlooked, but likely far more common than the one specimen that was collected. This study of blade-forming Ulva species confirms that a concerted effort, using DNA sequencing, is needed to document the seaweed flora of the Galápagos Archipelago.

Misapplication of Ulva epithets in GenBank has led to confusion in the scientific literature and community. To solve some of the problems, targeted DNA sequencing of plastid encoded rbc L gene amplicons or high-throughput sequencing was performed on all blade-forming Ulva type specimens from the northeast Pacific. Recently collected specimens from at or near type localities were also analyzed for some taxa. Based on these genetic analyses, we confirmed currently recognized species: U. californica , with U. angusta and U. scagelii as heterotypic synonyms, U. stenophylla , U. taeniata , and U. tanneri . Ulva dactylifera , currently considered a synonym of U. taeniata based on morpho-anatomy, is recognized as a distinct species, as is U. expansa whose type specimen was sequenced in 2018. All but two of the ITS, rbc L and tuf A sequences in GenBank that were labeled U. californica were correctly named, in contrast to U. taeniata , for which only one of 14 sequences was correctly labeled. These results show that DNA sequencing of Ulva type specimens is essential for the correct application of names.

The 2007 flora “Green Seaweeds of Britain and Ireland” did not present the molecular data underpinning the Ulvaceae treatment, mostly ITS sequences. Subsequently, names have changed as type material of Ulva species is sequenced and intensive sampling with DNA barcoding adds new European species. To update the Ulvaceae, we systematically sampled from 2007 to 2021, identifying specimens using various molecular markers alongside DNA from type material of four species. We show here that Ulva gigantea , based on rbc L, tuf A and ITS sequences of its holotype, is assigned to Ulva compressa , as is the lectotype of Ulva curvata . Ulva gigantea sensu GenBank and Ulva pseudocurvata are conspecific. The correct name is U. pseudocurvata based on rbc L sequences of the lectotype. Two species of monostromatic Ulvaceae were included in the 2007 flora, but we show that both of them and all earlier British monostromatic collections represent Ulvaria splendens , a species originally described from Alaska. Analysis of two rbc L amplicons of the Ulva sordida lectotype shows that it is conspecific with Ulvaria splendens . Our first genuine collections of Ulvaria obscura from SW England and SW Wales correspond to topotype material from the Bay of Biscay, recent samples from Galicia and unpublished tuf A sequences from Britanny.