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Survival of mangrove seedlings under flooding depends on their tolerance and adaptation. This study investigated the effects of flooding on rhizosphere conditions: porewater dissolved oxygen (DO), pH, and soil oxidation–reduction potential (ORP) and photosynthetic and antioxidant activities (superoxide dismutase [SOD] and guaiacol peroxidase [POX] activity and glutathione [GSH] content) of Rhizophora mucronata seedlings. The experiment lasted 20 days with three treatments: control (with drainage), waterlogging (10 cm of water above the soil surface) and submergence. Our results demonstrate that waterlogging and submergence resulted in a reduction in porewater DO, pH and soil ORP from day 5 into the treatment. Submergence resulted in lower maximum electron transport rates, lower saturating irradiance and higher light utilization efficiency from day 5 onwards, but stomatal closure was detected in both flooded treatments. POX activity and GSH content in the roots were increased by submergence. On day 5, submerged plants showed higher root POX activity than the other two treatments and higher root GSH content than controls. However, these parameters decreased on day 20, so that no difference among the treatments remained. As persistent flooding was shown to hamper the physiological performance of mangrove seedlings, extreme weather events and sea-level rise should be closely monitored.

Jørgen Koch introduced mycologists to a unique habitat for marine fungi, namely the sand dunes of Grønhøj, Jutland, Denmark. The high diversity of marine fungi obtained from the site provided abundant sporulating structures for a number of research areas in marine mycology including ecological surveys, ultrastructure examination of ascospore appendage development, spore attachment studies and phylogeny. This review highlights the key observations in these areas. Also, a list of 102 species of marine fungi documented for Denmark is provided.

Complete and/or partial DNA sequences for the plastid-encoded rbc L gene and the 5′ end of the mitochondrial cytochrome oxidase I (COI-5P) gene were used to re-examine the systematics of Hypnea species (Cystocloniaceae, Rhodophyta) from North Carolina, USA. These data, combined with light microscopic observations, indicate that two species ( Hypnea cryptica and H . musciformis sensu stricto ) are present in nearshore waters of coastal North Carolina. Molecular and morphological analyses with topotype material of Hypnea volubilis from North Carolina offshore waters revealed that it and Calliblepharis saidana are conspecific. Hypnea volubilis is proposed as a heterotypic synonym of C. saidana . This is the first report of Calliblepharis from the United States Atlantic coast and only the second report from the western hemisphere.

This study aims to identify different populations of Gracilariaceae collected from the central coast of Portugal through light microscopy, anatomical observations and genetic tools, essential approaches to correctly assign species identity. Samples were obtained from Ria de Aveiro (AV), Figueira da Foz (FFBC, FFMD), and Lagoa de Óbidos (LOBR, LOEV, LOBS). Although histological observations offered a visual representation of the characteristic pseudoparenchymatous organization, they did not allow a clear distinction among the species. The amplification of a ∼700 bp fragment of the mitochondrial cytochrome oxidase I gene, and its sequencing enabled us to assign the populations FFBC and LOBS to Gracilaria gracilis , and the populations AV, FFMD, LOBR, and LOEV to Agarophyton vermiculophyllum . This contribution will help phycologists to correctly identify the Portuguese populations of Gracilaria sensu lato at the species level, which will be crucial in ensuring that future studies and industrial exploration accurately target the correct species.

The present study reports the recent occurrence and expansion of Rugulopteryx okamurae in the Azores archipelago (NE Atlantic). Morphological and molecular characters confirmed the species identification. Quick surveys around the island of São Miguel showed that it has successfully colonized the island and is quickly expanding. In some locations, R. okamurae is currently the dominant organism smothering all other benthic biota and posing a serious threat to the benthic ecosystems across the region. The species first record dates from 2019 near the main harbour of the island, suggesting that its introduction was driven by human-assisted transport, via boat ballast waters or adhered to ship hulls and likely originating from the Mediterranean populations that have been proliferating in recent years across the Strait of Gibraltar.

The lipid and fatty acid profiles of 14 marine macroalgal species from the Madeira Archipelago, including two green (Ulvales and Dasycladales), three red (Corallinales, Bonnemaisoniales, and Ceramiales) and nine brown (Fucales, Dictyotales, and Sphacelariales) species were characterised in order to determine their potential use for animal and human nutrition. The total lipid content of species analysed was generally low, varying from 0.2 to 5.2% of dry weight. All species presented an omega 6/omega 3 (n-6/n-3) ratio lower than 10, as recommended by the World Health Organization for proper human health. Polyunsaturated fatty acids (PUFA), including linoleic acid and alpha-linolenic acid were exceptionally high in the green macroalga Ulva sp. Red macroalgae were rich in n-3 long-chain PUFA, particularly Asparagopsis taxiformis, which contained 6.6% of docosahexaenoic acid, and Halopithys incurva with 9.3% of eicosapentaenoic acid. Within Ochrophyta, Dictyota dichotoma is an interesting source of n-3 PUFA due to its high stearidonic acid proportion (8.0%). In addition, H. incurva contained a high proportion of both mono- and digalactosyldiacylglycerols. According to their lipid profiles, most macroalgae analysed might be considered of particular interest for their potential exploitation for human nutrition and livestock and aquaculture production.

In the present study, alginate yield and composition were investigated during the seasonal life cycle of the alien brown alga Sargassum muticum harvested from the Atlantic coast of Morocco. Alginate yield ranged from 11.14% in winter to 25.62% in spring/early summer, coinciding with maximum vegetative growth. Monthly monitoring of the alginate block structure showed that the highest mannuronate (M)/guluronate (G) ratio was recorded during the maximum development of S. muticum , before sexual maturity and during resumption of vegetative growth, giving maximum flexibility to the alga. The unusually high molar monad fractions (F G ) and dyad fractions (F GG ) of guluronic acid in late summer/early autumn appeared to be related to stiffness of senescent thalli. Rheological characterisation showed that the alginate of S. muticum exhibited pseudoplastic behaviour, with the highest apparent viscosities measured in late summer/early autumn when the G blocks dominated the alginate structure. This study suggests that S. muticum could be exploited as an alginophyte for commercial applications. The best harvest time is May-June, which corresponds to the highest alginate yield, maximum thallus growth, and largely completed sexual reproduction, ensuring sustainable exploitation of the species.