Journal of Applied Phycology最新文献

Global consumption of nori, a widely consumed commercial edible algal film, is predominant in Asian countries. As the demand for Asian cuisine rises in Brazil, there is a growing need to explore alternatives to importation, such as producing edible films using seaweeds from the Brazilian coast—specifically Ulva lactuca and Kappaphycus alvarezii. In this study, seaweed film formulations varied in concentrations, from 80% U. lactuca and 20% K. alvarezii to an equal proportion of 50% of each alga, heating at 90°C for 3 and 5 minutes. Results showed that the filmogenic suspensions had a pseudoplastic behavior, with viscosity decreasing as K. alvarezii concentration increased. The resistance of heated gels increased with higher K. alvarezii concentrations and prolonged heating times. Surface uniformity improved with elevated K. alvarezii concentration and extended heating time. As K. alvarezii concentration increased, films exhibited less intense coloration, heightened transparency, and increased solubility. Films with higher K. alvarezii content demonstrated greater tensile strength, albeit without an increase in elongation capacity. Sorption isotherms exhibited a characteristic Type II pattern, and modeling using the GAB model suggested stronger bonds in treatments with extended heating times. Despite the need for enhanced flexibility, the results indicate potential applications in snacks or as alternatives to nori. Notably, these films were produced solely with seaweeds and water, aligning with Nori's minimalistic approach. Treatments with a concentration of 60% U. lactuca and 40% K. alvarezii proved to be the most promising. This study lays the groundwork for future research in developing edible films derived from seaweeds.

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Understanding spatio-temporal variability in the production of drift macroalgae is useful for monitoring and assessing the influence of local anthropogenic nutrient sources on coastal ecosystems. In this study we: (1) assessed how the drift macroalgal community composition and biomass have changed over a 22-year period in Port Phillip Bay (a large coastal embayment in Victoria, Australia); and (2) measured the amount of accumulated nitrogen in drift macroalgae and the contribution of anthropogenic nitrogen sources through isotopic analysis. The surveys revealed little overlap in species composition (<13%) and a significant decrease in standing stock biomass (from 631 to 49 g m^-2) between surveys (1995/1996 and 2017/2018). This was associated with a high degree of turnover (β-diversity) at the genus level between surveys (mean – 0.53), resulting in distinct communities at all sites, particularly among red algal genera. In addition, the occurrence of ephemeral macroalgal blooms and a semi-perennial mat of the red macroalga Botryocladia sonderi at 10-15 m depth at locations close to nutrient sources indicate drift macroalgae are important nutrient accumulators in the bay. Isotopic analysis revealed a high contribution of anthropogenic-derived nitrogen (δ¹⁵N > 17‰ and ~ 3% N content) at depths and locations close to nutrient sources, particularly at times of the year when large wastewater discharges occur. Harvesting of drift macroalgae could be a cost-effective solution for offsetting nitrogen inputs from anthropogenic sources, but it will be important to first investigate whether harvesting results in negative impacts to associated fauna or nutrient cycling.

As harmless alternative of antibiotics, two antimicrobial peptides (AMPs), including anti-lipopolysaccharide factor isoform 3 (ALFPm3) and cathelicidin (CATHPb1), were co-expressed in the common fish food Tetraselmis subcordiformis. Lysates from T. subcordiformis transformant were able to inhibit the bacterial growth of Staphylococcus aureus, Vibrio parahaemolyticus, and Vibrio splendidus. To test the effects of AMPs in vivo, turbot (Scophthalmus maximus) underwent three dietary treatments, including commercial feeds (CON group), commercial feeds mixed with wild-type T. subcordiformis (WT group), and commercial feeds mixed with a mutant strain of T. subcordiformis (CSD group). Compared to CON group, both CSD and WT groups showed an increase in both the relative abundance and diversity of beneficial bacteria. The content of malondialdehyde was reduced and the enzymatic activities of lysozyme were increased in plasma. Comparisons of the biochemical factors in CSD group with those in CON group revealed that the relative abundance of Vibrio was decreased from 92.7% to 75.1%, and the number of bacteria containing the potentially pathogenic phenotypes was reduced. In the CSD group, the enzymatic activities of catalase and the expression levels of IgM, NKEF, IFNγ, MHC I, and IL-8R were higher compared to the WT group, whereas the levels of both TNFα and IL-1β were reduced. These results indicated that as an oral delivery vehicle for the AMPs, T. subcordiformis transformant improved the immunity, inflammatory response, and gut microbiome community of turbot.

A fixed off-bottom Kappaphycus striatus var. sacol farm was monitored for 12 months (June 2019 to May 2020) and the monthly incidence of disease and pests was recorded. Meteorological information in situ, from the nearest synoptic station and online data were collected to determine the relationships between temporal environmental changes and the incidence of seaweed health problems. The results showed that “ice-ice” disease (IID) was observed in dry months (i.e., from February to April 2020) and was significantly influenced by increased irradiance, salinity, sea surface temperature, and wind speed (p=0.004‒0.030). Also, the IID incidence was positively affected by reduced precipitation, storm surface run-off, water current speed, and inorganic nutrient (nitrite and ammonia) levels (p=0.002‒0.019). In comparison, epiphytic filamentous algae (EFA) were observed in wet months (i.e., from September to December 2019), with incidence varying from low to very high (≤25–100%) as the culture progressed. EFA incidence was significantly influenced by reduced salinity and increased storm surface run-off and inorganic nutrient (nitrate and ammonia) levels (p=0.006‒0.040). An intense tropical cyclone struck the farming area in December 2019, resulting in partial die-offs of farmed seaweed. Such seaweed health problems are expected to become more prevalent in the coming years as weather disturbances brought about by changing weather patterns become more frequent and intense. Hence, mitigation and preventative approaches must be fully considered to sustain the industry’s growth while protecting the livelihoods of many coastal communities dependent on seaweed farming.

Tripos is one of the largest dinoflagellate genera with ~800 reported taxa widely distributed in global marine ecosystems. These diverse Tripos species are ecologically important as critical primary producers and some Tripos species are also harmful algal bloom (HAB) species that may pose significant negative impact on marine ecosystems. However, due to the high morphological intraspecific variability and plasticity of numerous Tripos species, morphology-based identification and tracking of their dynamic changes have been both technically challenging and inconclusive. In this project, we carried out metabarcoding analysis of Tripos species in Jiaozhou Bay (JZB) through amplifying and sequencing of the common molecular marker 18S rDNA V4. The analysis identified five Tripos species (T. furca, T. fusus, T. eugrammus, T. falcatus and T. massiliensis), including two (T. eugrammus and T. falcatus) identified for the first time in JZB, demonstrating the competitive strength of metabarcoding analysis. This analysis of time-series samples collected in JZB revealed interesting seasonal dynamic changes of Tripos species, with different species demonstrating differential seasonal preferences. This analysis also suggested the possible existence of 11 additional Tripos species in JZB. The inconclusive identification of these 11 potential Tripos species indicated that the resolution of the common molecular marker 18S rDNA V4 applied in this study is inadequate and that the molecular reference data for Tripos is still limited. Selection of molecular markers with higher resolution (such as 28S rDNA D1-6) and the completion of reference sequences of Tripos species may facilitate more accurate identification of and tracking of their dynamic changes.

We explored the effect of supplementation of two tropical red seaweeds, Kappaphycus alvarezii (KA) and Gracilaria salicornia (GS) at three different levels (0, 1.5 and 3%) on nutrient utilization, gut health, antioxidant, and immune status in adult dogs. The experiment was based on a 5 x 5 Latin square design (LSD) comprising five adult Labrador dogs, five dietary treatments (CON: basal diet; KA_L: KA at 1.5 % of diet dry matter (DM); KA_H: KA at 3 % DM; GS_L: GS at 1.5 % DM; GS_H: GS at 3 % DM) and five periods, each of 21 days, followed by a 7-day washout period in between. The palatability, food intake, and body weight changes were comparable among the groups (P>0.05). The supplementation of two seaweeds at either level did not have any effect on nutrient digestibility (P>0.05). The fecal lactate concentration was higher (P<0.05) in GS_L and GS_H groups whereas fecal ammonia was lower (P<0.05) in the GS_H group in comparison to the other groups. The volatile fatty acids (VFA) profile improved (P<0.05) in the KA_H, GS_L, and GS_H groups. The mean fecal Lactobacillus count tended to increase (P<0.10) in the KA_H and GS_H groups while the coliform count remained unaffected by seaweed supplementation. The mean fecal Bifidobacterium population was higher (P<0.05) and the mean clostridial population was lower (P<0.05) in the GS_H group as compared to -other groups. The concentration of reduced glutathione (GSH) was higher (P<0.05) and lipid peroxides were lower in the KA_H and GS_H groups. A tendency (P<0.10) of improved cell-mediated immunity (CMI) was observed in the GS_H group as compared to other groups. Overall, the supplementation of either of the seaweeds at 1.5 % failed to exert significant influence on any of the parameters studied except fecal VFA and lactate levels, whereas both the seaweeds at 3% level showed some promising benefits in terms of improved gut health, antioxidant, and immune status and the best response was obtained in GS_H group. Hence, it can be concluded that supplementation of GS at the 3 % level outperformed KA supplementation at the 3 % level by improving gut health, antioxidant status and immunity.

Biostimulants such as seaweed extracts are widely used to stimulate plant growth and crop productivity under optimal or stressful conditions, constituting a sustainable strategy to mitigate the impacts of abiotic stress on plant performance. In this study, a growth experiment was conducted to evaluate the effects of an aqueous extract from the seaweed Padina gymnospora on the physiological, biochemical, and molecular characteristics of Solanum lycopersicum under salt stress. The experiment included four treatments: 1) control plants, 2) plants irrigated with 300 mM NaCl solution, 3) plants treated with the P. gymnospora extract, and 4) plants treated with the P. gymnospora extract and irrigated with 300 mM NaCl solution. Salt stress increased the activity of antioxidant enzymes (catalase and superoxide dismutase) and resulted in the overaccumulation of the osmolyte proline and flavonoids while enhancing photosynthetic performance and chlorophyll content. In addition, treatment with P. gymnospora extract increased total reducing sugars and phenols in salt-stressed plants, which was correlated with DPPH and ABTS antioxidant activity. The induction of stress-responsive genes, such as SlHB7, SlSOD1, SlRD29, and SlHKT, appears to be a major factor modulating the responses to P. gymnospora extract application in tomato plants. The results of this study demonstrate that the application of P. gymnospora to tomato plants attenuated the damage caused by salt stress. It is essential to continue studying the potential of seaweed extracts to mitigate stress in plants, given the promising agricultural applications of these novel biostimulants.

The yield of Gracilariopsis lemaneiformis in China was reduced by at least 40% in 2023 compared with 2022. Based on the investigation of this study, the decrease in production was caused by a disease locally named ‘Baotou’. The first sign of ‘Baotou’ disease was observed with the appearance of many light red branches in the thalli of G. lemaneiformis. During the onset of ‘Baotou’ disease, G. lemaneiformis lost its original red color and eventually decayed. One of the most typical morphological characteristics of ‘Baotou’ is that the closer the thalli were to the attachment rope, the more they decayed. Compared with the flat and regular epidermal cells of healthy alga, diseased algae had a rough surface covered with mucilaginous substance and numerous bacteria were found within the mucilaginous substance. The number of decayed points was significantly increased when the healthy cuttings were placed near the ‘Baotou’ cuttings. Pathogenic bacteria, which can induce the decay of healthy G. lemaneiformis, can be obtained from the ‘Baotou’ diseased G. lemaneiformis. The ‘Baotou’ disease is contagious. Once the G. lemaneiformis are infected with ‘Baotou’ disease, they should be harvested timely to prevent them from infecting the healthy alga.

This study employed 1-ethyl-3-methyl imidazolium chloride ([EMIM][Cl]) as an additive in an aqueous medium, combined with microwave-assisted extraction (IL-MAE), to extract total lipids and eicosapentaenoic acid (EPA) from the microalga Nannochloropsis sp. microalgae. The optimization process involved evaluating critical operating parameters, including the type of extraction solvent, solid-loading (i.e., water: microalgae ratio), extraction time, extraction temperature, and the IL/biomass ratio on the extraction of total lipids and as well as its EPA content. Under optimal conditions, IL-MAE significantly enhanced total lipid yield and EPA content by approximately 2.72 times and 8.1 times, respectively, compared to the traditional Soxhlet extraction. The standard Soxhlet procedure resulted in approximately 6.20% total lipids and 4.61 mg g^-1 of EPA. Notably, with IL-MAE, the highest lipid and EPA yields were achieved. These reached 16.87% and 37.28 mg g^-1, respectively, under optimal conditions: 90 °C for 25 min, using 2 w/w IL/biomass ratio, with 0.5 g of algae and a 3.3% w/v solid-loading. The obtained FAMEs through transesterification of total lipids exhibited high quality, comprising 37.94% wt polyunsaturated fatty acids (PUFAs). SEM and FTIR confirmed IL-MAE's superior lipid extraction by disrupting glycosidic linkages in the microalgal cell wall, resulting in a significantly higher yield than Soxhlet extraction. Repeated use of recycled [EMIM][Cl], tested up to four times, did not impact lipid and fatty acids recovery. Cost evaluation revealed that the IL-MAE approach for lipid production from Nannochloropsis sp. is more cost-efficient than the Soxhlet method, considering biomass, chemical and energy consumption. The enhanced extraction performance and accelerated rates of the IL-MAE system demonstrate its efficacy in extracting lipids, EPAs, and PUFAs from microalgae. Furthermore, it emphasizes sustainable, green, and efficient approach for extracting bioactive compounds, offering potential applications in the pharmaceutical and nutraceutical industries.

The prediction and numerical modeling of cyanobacterial outbreaks have emerged as a significant research topic. Presently, in-situ and remote sensing observations serve as the primary foundation for numerical modeling. Owing to the influence of local environmental factors on fieldwork-based models, cross-sectional comparisons among distinct models remain challenging. In this study, three tanks (height: 1.8m) were installed in the laboratory to represent the structure of vertical zone in shallow lakes, and Microcystis aeruginosa culture was observed under a 12/12 light cycle for one month maintaining constant conditions. The findings indicate that light intensity, duration, and light-dark cycling all impact vertical migration of M. aeruginosa. Microcystis aeruginosa exposed to low light intensities (18 to 39 μmol photons m^-2 s^-1) migrated more rapidly than those under high light intensities (447 to 466 μmol photons m^-2 s^-1); cells subjected to extended illumination (over 8 hours) exhibited stable distribution patterns; and, in darkness, cyanobacteria that were in high light intensity areas responded more swiftly compared to those that were in low light intensity areas. The findings suggest that M. aeruginosa vertical migration is continuous and dynamic, and not vitally light intensity dependent. To effectively conduct cross-sectional comparisons of models across lakes, it is imperative to thoroughly consider the diurnal variation of vertical migration of M. aeruginosa. Based on the research results, recommendations for changes to the current vertical migration numerical model are provided.