Journal of Applied Phycology最新文献

The potential of seaweed aquaculture is restricted by high labor, production and processing costs, leading to low economic viability. Selective breeding can improve yields and cultivation efficiency, thereby decreasing production costs. Until now, genetic resources as input for Saccharina latissima breeding trials have been sourced strictly locally, due to concerns regarding outplanting genetically exogenous material in local waters. Here we study, for the first time, worldwide interregional fertility of the seaweed S. latissima, in order to assess the potential of including global S. latissima genetic resources for selective breeding with regard to heterosis. We quantified the yield (as an indicative aquacultural performance) and morphological traits of intra- and interregional S. latissima hybrids originating from a broad range of locations in a common garden experiment. Our results show that the practical application of worldwide S. latissima genetic resources in breeding programs is feasible based on global interfertility. We found a wide morphological diversity of hybrids and observed significant heterosis in interregional hybrids. The degree of heterosis could not be linked to geographic distance. These findings reveal that worldwide genetic resources can considerably contribute to S. latissima breeding programs and could offer a major next step in improving yields and quality traits.

Supplementary information: The online version contains supplementary material available at 10.1007/s10811-025-03447-7.

Seaweed farming is a rapidly growing global industry, driven by increasing demand for biomass with a range of commercial applications. A major barrier limiting expansion of the industry is the need for cost-effective approaches to production. Established twine seeding methods are reliable, but recently developed binder methods offer potential scalability while minimising hatchery costs. Here, we compared growth of the farmed kelp Saccharina latissima using these two seeding methods. We also examined the influence of water depth on biomass production within a vertical cultivation system. Twine consistently achieved greater S. latissima biomass yield, with mean biomass almost four times higher than from binder seeding, and sporophytes reaching significantly greater density and total length. The biomass, length and density of S. latissima decreased with increasing water depth, a pattern which was more pronounced with twine seeding. We also observed morphological variability, with larger individuals on twine compared with binder treatments at all depths. Natural settlement of the non-target macroalga Sacchoriza polyschides was also recorded, at significantly greater biomass on binder treatments and at greater depths. Further work is needed to examine the predictability and extent of natural settlement of S. polyschides, and its potential as a commercially-viable species. Overall, twine seeding methods out-performed binder at a relatively dynamic, open coast, small-scale cultivation site. Moreover, while vertical cultivation systems can maximise yield relative to the spatial footprint of a seaweed farm, the marked reduction in cultivated biomass with increasing water depth should be considered within the local environmental context.

A global rise in kelp aquaculture has resulted in an increased demand for high quality and quantity kelp seedstock, yet many bottlenecks remain to sustainable scale-up solutions. One such bottleneck is increasing biomass quickly and efficiently in the nursery phase of the kelp cultivation cycle. The microscopic gametophyte is leveraged during this phase, using red light to stimulate vegetative growth and delay onset of gametophyte fertility until deployment. However, red light may make the gametophyte less photosynthetically efficient and thus slow growth. A solution may be growing gametophytes in blue light, which can increase production, while changing the nutrient composition of the media to repress fertility. Here we test the efficacy of light source (blue and red), two common media types (PES and f/2) and iron supplementation on the growth, fertility and photosynthetic parameters of Alaria esculenta gametophytes, a commercial kelp species. We found the highest biomass was achieved under blue light with iron-free f/2. Similarly, pigment concentration was higher in blue light and iron-free f/2, while gametophytes were found to have more shade-adapted pigment characteristics under red light. Red light strongly supressed formation of sporophytes and while withholding iron did not supress fertility in blue light, it did result in less malformed sporophytes. Based on this research, we recommend growing A. esculenta gametophytes in iron-free f/2. Failure of iron-free media to supress fertility in blue light may be due to iron retention of gametophytes or trace levels of iron in seawater, which warrants further research.

Supplementary information: The online version contains supplementary material available at 10.1007/s10811-025-03665-z.

Macroalgal extracts offer an alternative option to increase crop yields and plant performance whilst reducing reliance on inorganic chemical fertilisers. Macroalgae have high concentrations of bioactive compounds capable of enhancing crop growth, stress tolerance and pest resistance. This study investigated whether seasonal variation in the chemical composition of three brown seaweeds Ascophyllum nodosum, Fucus serratus and Fucus vesiculosus affected plant growth in Arabidopsis thaliana, Beta vulgaris and Lactuca sativa through different extract concentrations. Crops were treated with 1:20, 1:50 and 1:100 dilutions from macroalgal extracts and compared to controls tap water, deionised water and one commercial macroalgae-based fertiliser made from A. nodosum. Dry weight assessment results revealed that moderately diluted dosages had better effects on plant growth than concentrated dosages, showing that the most suitable concentrations of all macroalgae extracts are 1:50 for Arabidopsis; no trend was detected in B. vulgaris or L. sativa growth. Overall, there were peaks of increased plant growth when treated with extracts harvested in June and August, which correlates with fertility peaks in commercial brown macroalgae in the wild. These results suggest that the optimal harvest for A. nodosum, F. serratus and F. vesiculosus for plant stimulant products should occur between May and August at sustainable harvest levels. Soil respirometry trials using the extracts showed no differences in CO₂ fluxes between the macroalgal species, different harvesting seasons, or correlation with plant biomass. It is therefore likely that macroalgal extracts impact the plant directly and produce minor impact on soil microbiota. Thus, these results support the use of macroalgal fertilizers as a low-cost and environmentally friendly alternative to chemical fertilisers.

Red microalgae from the Cyanidiophyceae, particularly Galdieria sulphuraria and Cyanidioschyzon merolae, are primitive photosynthetic thermoacidophiles that thrive in acidic hot springs and geysers. Unlike most Cyanidiophyceae, Galdieria strains are metabolically flexible as they can switch from photoautotrophic growth in the light to heterotrophic growth in complete darkness. Galdieria sulphuraria is especially noteworthy for its accumulation of various commercially valuable, functional compounds such as glycogen and phycocyanin. Glycogen, a branched fractal-like polysaccharide composed of several thousands of anhydroglucopyranose units, can be added to cosmetic products and sports drinks as a moisturizer or slow-digestible carbohydrate. While the production and structural characteristics of the glycogen of G. sulphuraria 108.79, isolated from Yellowstone National Park, have been previously described, our investigation aimed to explore glycogen production and properties across various Galdieria strains from different locations. Our findings reveal that all examined strains produce substantial amounts of highly branched glycogen when grown heterotrophically on glycerol in the dark. Notably, the structural characteristics of Galdieria glycogen distinguish it from both eukaryotic and prokaryotic glycogen, exhibiting a significantly higher degree of branching, substantially shorter side chains, and a considerable extent of indigestibility. These findings support the hypothesis that this highly branched, small glycogen is a long-term energy store, enabling survival during extended periods of complete darkness.

Cyanobacteria, a group of prokaryotic photoautotrophs, are accredited for trace metal sequestration due to their ability to produce various siderophores and are widely utilised for bioremediation. In this context, we investigated the ability of cyanobacterium Anabaena oryzae for removal of cadmium. Cadmium toxicity disrupts crucial physiological processes in photosynthetic organisms, inhibits growth, reduces photosynthetic efficiency, etc. thereby, truncating nutrient cycling. Structural elucidation of siderophore produced by A. oryzae through FTIR, mass spectrometry, 1D and 2D NMR (COSY, HSQC and NOESY) depicted tetradentate denticity and conspicuous presence of dihydroxamate along with unique spatial arrangement of atoms, conferring novel structure. Furthermore, the physiological and biochemical studies by administering iron and cadmium, individually as well as in combinations, exhibited cadmium-mediated toxicity in the cyanobacterium, ultimately reducing physiological capacity, whereas iron possessed ameliorating effect. Nevertheless, the possibility of Cd-induced siderophore production was shown by higher production of siderophore in presence of cadmium. Proteome profiling further displayed regulation of siderophore synthesis through cadmium supplementation. Moreover, negative binding energies of transporter proteins like OmpA, Pbp, ABC type-transporter and TonB with siderophore-Cd complex, shown by in silico docking studies, suggested uptake and thereby removal of cadmium by A. oryzae. This study addresses the problem of cadmium toxicity in cyanobacteria and explores the potential of A. oryzae to mitigate this toxicity through siderophore production and metal removal. It also contributes to the understanding of siderophore-mediated metal sequestration and introduces a novel siderophore candidate with promising prospects for cadmium remediation.

The application of macroalgae for food and feed has been increasing continuously due to their nutritional and health-promoting properties. Efficient post-harvest drying is needed to remove moisture content from macroalgal biomass without negatively affecting its nutritional value. We hypothesized that low-temperature oven drying would preserve most of the nutrients and polyphenols in macroalgae. The polyphenol-rich brown macroalga, Fucus vesiculosus, was exposed to one of the following treatments: freeze-drying (FD; for 72 h), oven drying at 40 ℃ (OD40; for 24 h), and oven drying at 80 ℃ (OD80; for 24 h). The concentration of total fatty acids and the sum of saturated, mono-, and polyunsaturated fatty acids exhibited a decreasing trend with higher drying temperatures (FD > OD40 > OD80), indicating the sensitivity of fatty acids to a high drying temperature. However, the sum of total or essential amino acids was significantly higher (p < 0.05) in OD80 compared to OD40 and FD biomass. In this study, the average N-protein-conversion factor for dried F. vesiculosus remained relatively stable (~ 4.64) across drying treatments. The total polyphenol content remained unaffected by the drying treatment, although it tended to decrease with increasing drying temperature. Targeted metabolomics revealed three classes of phenolic compounds: phenylpropanoids, flavones, and flavonols. A low-temperature oven drying appears to be a suitable method to preserve nutrients and polyphenols in brown macroalgae. Future studies are needed to evaluate the impact of drying methods on other bioactive compounds and to understand the economic sustainability of oven drying.

This experiment was carried out to evaluate the effect of dietary supplementation of three different tropical seaweed species on rumen fermentation, methane emission, antioxidant status, immunity and milk production in lactating Murrah buffaloes. Twenty-four lactating Murrah buffaloes were divided into four groups of six each in an experiment based on randomized block design (RBD) and were fed to meet their nutrient requirements (ICAR 2013). Animals in control (CON) group were fed basal diet without any supplemental seaweed, however, Kappaphycus alvarezii (KA), Gracilaria salicornia (GS) and Turbinaria conoides (TC) were supplemented at 1% of the dietary dry matter in KA, GS and TC groups, respectively. Intake and apparent digestibility of nutrients, plasma concentrations of selected blood metabolites, and thyroid hormones were similar among the groups. Supplementation of KA and GS, but not TC increased (P < 0.001) the proportion of propionate in rumen fluid with a concurrent decrease (P < 0.001) in acetate: propionate. The enteric methane emission was lower (P < 0.05) in KA, GS groups and the maximum values were observed in groups CON and TC. Total antioxidant capacity (TAC) and immune response (cell-mediated and humoral) were higher (P < 0.001), and MDA was lower (P < 0.001) in seaweed-fed groups as compared to CON; the higher response was observed in group KA, followed by TC and GS. Plasma concentration of cortisol was lower (P < 0.001) in group KA as compared to other groups. Milk yield and the 6% fat-corrected milk (FCM) yield (kg day⁻¹) were higher (P = 0.009) in KA, followed GS, corresponding values in group TC were not significantly different than those of group CON. Thus, supplementation of the tropical red seaweed improved antioxidant status, cellular and humoral immunity, and milk yield; the greater response was obtained when KA was used as feed supplement. It is concluded that supplementation of K. alvarezii at 1% of dietary DM of lactating Murrah buffaloes would improve antioxidant status, immunity and milk yield with reduction in enteric methane emission.

In the field of industrial microalgae production, the introduction of parasitic contaminants is an often-neglected topic, but one that represents a major risk with potentially significant financial implications. So far, no successful strategy exists to maintain a long-term stable cultivation environment in industrial photobioreactors. To create a strategy for preventing and controlling parasitic contamination, methods from synthetic ecology were used, replacing monocultures with mixed-biocoenoses. The goals were the identification of microbiotic ecosystems of potentially symbiotic bacteria and the utilization of synergistic effects between bacteria and algae to stabilize cultures. The final aim was to combine the findings with abiotic factors influencing the infections. As model organisms, the microalga Coelastrella vacuolata (formerly Scenedesmus vacuolatus) and the parasitic contaminant Amoeboaphelidium protococcarum were chosen. For this case, a correlation between infection rate and the chlorophyll a fluorescence in the culture was found. Algal co-cultures with specific bacteria were tested using the protecting effects of antiphytopathogenic, extracellular substances. This led to the bacterium Pseudomonas protegens and the naturally antipathogenic phenol 2,4-diacetylphloroglucinol (DAPG). Co-cultures with DAPG-producing P. protegens effectively inhibited the infection even though no quantifiable amounts of DAPG were found in the culture. Furthermore, abiotic influences on the infection process were identified, resulting in the implementation of a light–dark-cycle with induced anaerobic conditions in the dark phase. With these findings, conditions that inhibit the growth of parasitic contaminants could now be introduced preventively within standard cultivation procedures.

Fulvic acid (FA) is an active humic substance and is found to improve the antioxidant defence system under unfavourable conditions. Dunaliella salina is a unicellular microalga and is a rich source of β-carotene. In this study the impact of fulvic acid (FA) was investigated on some physiological parameters, H₂O₂ production, antioxidant metabolites, and enzymatic responses related to the ascorbate (ASA)-glutathione (GSH) pathway in D. salina. Results showed that 100 mg FA L⁻¹ maintained the D. salina cell growth compared to control, and exhibited as a suitable treatment to induce carotenoids compared to 50 FA mg L⁻¹. However, 200 FA mg L⁻¹ significantly decreased the cell biomass. FA (100 mg L⁻¹) enhanced the total carotenoids (3.92 pg cell⁻¹), β-carotene (2.46 pg cell⁻¹), and lutein (0.81 pg cell⁻¹) after 7 days, which was accompanied by a reduction in the chlorophyll a and b. Cell number did not change significantly under FA and cells trended to be round in shape after 7 days. Protein content showed an insignificant change, while H₂O₂ level was promoted by FA treatment, which was related to the regulation of the ASA-GSH pathway. The activity of ascorbate peroxidase, superoxide dismutase, and dehydroascorbate reductase was more promoted in the FA-treated cells, while glutathione reductase activity and glutathione content were just induced under Sevier oxidative conditions. The findings of this research suggest new insights into the inducing impact of FA on the ASA-GSH pathway and carotenoid biosynthesis to regulate the ROS level in D. salina.