Systematics of Hypnea (Cystocloniaceae, Rhodophyta) from coastal North Carolina, with a first report of Calliblepharis saidana from the United States Atlantic Coast

Complete and/or partial DNA sequences for the plastid-encoded rbcL 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.

Lipid characterization of 14 macroalgal species from Madeira Archipelago: implications for animal and human nutrition

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.

Identification of Gracilariaceae (Rhodophyta) of central Portugal by histological and genetic methods

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.

Experimental flooding modifies rhizosphere conditions, induces photoacclimation and promotes antioxidant activities in Rhizophora mucronata seedlings

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.

Seasonal patterns of growth, alginate content and block structure of the alien invader Sargassum muticum (Fucales, Ochrophyta) from the Atlantic coast of Morocco

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 (FG) and dyad fractions (FGG) 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.

Occurrence of thraustochytrids: the fungoid protists vis-a-vis marine macroalgae (seaweeds) along the coast of Goa, India

Thraustochytrids are fungoid protists ubiquitous in the marine environment and found to be associated with decaying macroalgae. Not much is known about their association with living macroalgae. Hence in the present study, different macroalgal samples were collected from various beaches of Goa to examine the presence of thraustochytrids during a four-year-long study. Brown, red and green algae were found to be substrata of thraustochytrids. Thraustochytrids were isolated on pine pollen baiting from 17 to 58% of the specimens. Thraustochytrids isolated from various macroalgae belonged to the genera Oblongichytrium, Schizochytrium, Ulkenia, and Thraustochytrium. Labyrinthula sp. was also found once on the green alga Bryopsis hypnoides. These were generally found during dry seasons rather than in monsoons. The seasonal occurrence of thraustochytrids was found to be associated with temporal variation in macroalgal diversity. The statistical analysis supported individual or interactive effects of both factors viz, seasons and macroalgal diversity, on the occurrence of thraustochytrids. Thraustochytrids were also isolated from seawater adjoining macroalgae and from estuarine water at all times of the year. Oblongichytrium sp. was isolated from the green alga Ulva compressa and Anjuna seawater samples at the same time, thus indicating that thraustochytrids from seawater could inhabit the macroalgae.

Characterization of cellular development and fatty acid accumulation in thraustochytrid Aurantiochytrium strains of Taiwan

Long-chain saturated and polyunsaturated fatty acids of two new thraustochytrid isolates cultured from Taiwan mangroves, Aurantiochytrium sp. IMB169 and Aurantiochytrium sp. IMB171, were characterized through their cell growth and development in relation to their intracellular lipid accumulation using transmission electron microscopy. Flow cytometry in combination with the lipophilic fluorescent dye BODIPY 505/515 was used to stain and characterize intracellular lipid bodies in the two isolates. The transmission electron microscopy and flow cytometry analyses revealed a progressive accumulation of lipid products in IMB169 and IMB171. Further, selective BODIPY stained cells were successfully separated and enriched using flow cytometry at single cell level. Among the two isolates, IMB169 was found to produce a high level of docosahexaenoic acid. The qualitative and analytical results obtained using electron microscopy and flow cytometry studies were validated by gas chromatography (GC). In addition, a quantitative baseline was established using cell growth, flow cytometry and GC analyses for developing an efficient bioprocessing methodology to selectively enrich thraustochytrids phenotypes with desirable characteristics.