Edible Seaweed Research Articles

Paying attention to the safety of global edible seaweeds after the discharge of nuclear-contaminated water from Japan

Macroalgae play a crucial role as primary producers in the ecosystem. The increasing human demand for macroalgae has led to the development of the macroalgae aquaculture industry, which is seen as a potential solution to future food shortages. However, the Japanese Government's plan to discharge nuclear-contaminated water, which is projected to continue until at least 2053 with a total volume of at least 1.3 million metric tons, poses a significant threat to the macroalgae industry, ecosystems, and human health. Macroalgae can accumulate radionuclides from nuclear-contaminated water, which may then be transferred to other marine organisms or humans through the food chain or web, and the long-term implications of this ‘butterfly effect’ remain uncertain. In principle, international supervision and regulations should govern the management of nuclear waste, further filling the gaps in international law, including all aspects of addressing complaints and prohibiting the discharge of nuclear-contaminated water, to ensure responsible management based on scientific evidence. However, the current Japanese government's determination to proceed with the discharge of nuclear-contaminated water has revealed deficiencies in international legislation and a lack of enforcement power within international regulatory organizations, which demand further improvement. Herein, we call upon phycologists specializing in the utilization of macroalgal resources, marine organisms, and marine ecology to pay further attention to and conduct in-depth investigations into the potential long-term impacts of this event. Regardless, against the backdrop of Japan's ongoing discharge of nuclear-contaminated water, the commitment to advancing the health and stability of the global macroalgae industry and safeguarding the rights of seaweed farmers represents a lengthy but highly significant scientific endeavor.

Perception and acceptance of high seaweed content novel foods (Ulva spp. and Undaria pinnatifida) across New Zealand and Singaporean consumers

Edible seaweeds are gaining global popularity as nutritious and sustainable food sources, extending beyond Asian into Western diets. To investigate consumer perception and acceptance of high seaweed content foods, two novel products, seaweed dumplings and pasta, were developed using the mixture of Ulva spp. and Undaria pinnatifida as a primary ingredient. Consumer evaluations were conducted in New Zealand (NZ, n = 157) and Singapore (SG, n = 176). Results showed low overall liking and willingness to purchase for both products in each country, though NZ consumers rated them more positively in terms of liking, healthiness and sustainability than SG consumers. Willingness to purchase was positively correlated with ratings of liking, healthiness, and sustainability. Emotional responses differed by country and product, with more NZ participants reporting positive emotions (e.g., pleased, happy, hopeful and loving) and dumplings evoking more activate emotions (e.g., energetic, shocked and amazed). Umami taste enhanced overall liking in both countries, while slimy texture (NZ) and fish-like flavour (SG) decreased overall liking. These results underscore the current challenges in consumer acceptance of high seaweed content novel foods, but also highlight cross-cultural differences that can guide the development of seaweed-based foods in global markets.

Anti-Melanogenic Activities of Sargassum fusiforme Polyphenol-Rich Extract on α-MSH-Stimulated B16F10 Cells via PI3K/Akt and MAPK/ERK Pathways.

Melanin overproduction leads to pigmented skin diseases. Brown algae polyphenols, non-toxic secondary metabolites, exhibit potential bioactivities. Sargassum fusiforme, an edible seaweed, has been underexplored in the field of beauty despite its polyphenol richness. Polyphenols from S. fusiforme were extracted using macroporous resin (SFRP) and ethyl acetate (SFEP). Their antioxidant and anti-aging properties, tyrosinase inhibitory activities, and mechanisms were assessed. The melanogenesis inhibition effect and mechanism by SFRP was examined in B16F10 melanoma cells. Both SFRP and SFEP demonstrated scavenging activities against DPPH, superoxide anion, and hydroxyl radicals. SFRP showed stronger anti-collagenase and anti-elastase effects. They dose-dependently inhibited mushroom tyrosinase, with IC50 values of 9.89 μg/mL for SFRP and 0.99 μg/mL for SFEP. SFRP reversibly inhibited tyrosinase, while SFEP showed irreversible inhibition. SFRP also suppressed melanin content and intracellular tyrosinase activity in B16F10 cells, downregulating the expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein 1 and 2 expression through the PI3K/Akt and MAPK/ERK signal pathways. S. fusiforme polyphenols, especially SFRP, exhibit promising antioxidant, anti-aging, and melanogenesis inhibitory properties, highlighting their potential application as novel anti-melanogenic agents in cosmetics and the food industry.

Investigating the Therapeutic Potential of Gracilaria edulis Extract in Copper-Exposed Zebrafish Embryos: An Anti-Inflammatory Perspective

Introduction: Harnessing the bioactive compounds from seaweed for inflammatory diseases holds great promise for developing new and effective treatments that are natural, sustainable, and potentially free from the side effects commonly associated with synthetic drugs. Method: The objective of this study was to examine the phytochemical levels, as well as the antioxidant and anti-inflammatory properties of the edible red seaweed Gracilaria edulis. The methanol extract of the seaweed showed potent radical scavenging activity. Analysis using GC-MS techniques identified two distinct phytochemical compounds in G. edulis extract, namely 1,1-dipropylhydrazine and 4-chlorobuten-3-yne. Results: When tested on copper-induced zebrafish embryos, the extract reversed the upregulation of MMP9 and NFκBp65, as evidenced by western blotting and zymography methods. Conclusion: These findings suggest that the bioactive compounds found in G. edulis extract could be utilized for the development of natural sources for antiradicals, food supplements, nutraceuticals, and various functional foods with therapeutic applications.

A polysaccharide from edible red seaweed Bangia fusco-purpurea prevents obesity in high-fat diet-induced C57BL/6 mice

The study aimed to investigate the impacts of a polysaccharide (BFP) from Bangia fusco-purpurea on high-fat diet (HFD)-induced obesity in C57BL/6 mice, as well as its underlying mechanisms. Our results showed that orally administrated BFP was more effective than inulin (INU) in reducing body weight and fat accumulation in obese mice, indicating its anti-obesity effect. BFP effectively improved the compositions and metabolites of intestinal microbiota in obese mice, leading to enhanced energy metabolism and lipid metabolism, thus contributing to its anti-obesity effect. Notably, the better anti-obesity effect of BFP compared to INU were attributed to their varying degrees of modulation of specific intestinal microbial taxa, such as Clostridium and Aerococcus, as well as the regulation of differential metabolites (including biotin, piperine, G6P, etc.) also varies. Also, both in vitro (3T3-L1 preadipocytes) and in vivo (HFD-induced obese mice) models confirmed that BFP achieved anti-obesity effect attributed to enhance energy metabolism, promote lipolysis, increase fatty acid oxidation, and inhibit adipogenesis via activating the AMP-activated protein kinase and Acetyl-CoA carboxylase signaling pathways and suppressing the peroxisome proliferator-activated receptor γ expression. Our findings suggest that BFP has the potential to be used as prebiotics, dietary agents, and nutritional supplements against obesity.

The memory-improving effect of Hizikia forsiforme functional oil microcapsule (HFFOM) prepared by subcritical extraction and complex coacervational embedding

Functional foods are prospective in improving memory decline caused by Alzheimer’s disease and aging. The Edible seaweed Hizikia fusiforme functional oil (HFFO) inhibited acetylcholinesterase, prevented cellular neuroinflammation, and improved memory deficits in zebrafish models in the previous studies. To realize its greener preparation and lipid oxidation mitigation and study its effects on higher animals, more investigations are necessary. Herein, sub-critical fluid extraction of HFFO and successive complex coacervation embedding yielded a water-soluble and anti-oxidative microcapsule HFFOM, which displayed in vivo memory-improving effects on LPS-injured zebrafish and normal rodents in different behavior tests. HFFOM can elevate the level of the neurotransmitter acetylcholine while decreasing the levels of MDA, IL-1β, and TNF-α in the zebrafish brain. LC-MS/MS and lipidomic analysis suggested its predominant memory-improving ingredients to be linolenic, erucic, nervonic, arachidonic, linoleic, eicosatrienoic, docosahexaenoic, and docosapentaenoic acids. This study enlightens the potential of HFFOM in developing memory-enhancing functional foods or drugs.

Europium anomaly as a robust geogenic fingerprint for the geographical origin of aquatic products: A case study of nori (Neopyropia yezoensis) from the Japanese market

Rare earth element (REE) concentration patterns, while essential in geochemistry for tracing sample histories, have yet to be utilised entirely in food origin authentication. This research analysed 13 heavy metal(oid)s and REEs in Japanese edible seaweed Nori sheet samples (Neopyropia yezoensis), showing that the concentrations mirror the laver cultivation area's geological features (island arc-trench systems vs. continental crust). Thresholds for cadmium (0.5 ppm) and thorium (3.3 ppb) differentiate Japanese products from Korean imports. The slope of REE pattern, gadolinium anomalies, and yttrium/holmium ratios were also examined. However, nori samples significantly conveyed europium (Eu) anomalies, aligning with the mariculture hinterland's geochemistry. Both Japan's major seaweed mariculture areas, the Ariake Sea and the Seto Inland Sea, and Korean imports revealed distinct Eu anomalies (Eu/Eu* = 0.81–0.90, 0.58–0.66, 0.71–0.77), underscoring the potential of Eu anomalies as reliable seafood origin verifiers. This was also confirmed by literature values of Chinese samples.

Detailed lipid investigation of edible seaweeds by photochemical derivatization and untargeted lipidomics

Seaweeds are macrophytic algae that have been gaining interest as alternative healthy foods, renewable drug sources, and climate change mitigation agents. In terms of their nutritional value, seaweeds are renowned for their high content of biologically active polyunsaturated fatty acids. However, little is known about the regiochemistry—the geometry and position of carbon–carbon double bonds—of free and conjugated fatty acids in seaweeds. In the present work, a detailed characterization of the seaweed lipidome was achieved based on untargeted HRMS-based analysis and lipid derivatization with a photochemical aza-Paternò–Büchi reaction. A triple-data processing strategy was carried out to achieve high structural detail on the seaweed lipidome, i.e., (i) a first data processing workflow with all samples for aligning peak and statistical analysis that led to the definition of lipid sum compositions (e.g., phosphatidylglycerol (PG) 34:1), (ii) a second data processing workflow in which the samples of each seaweed were processed separately to annotate molecular lipids with known fatty acyl isomerism (e.g., PG 16:0_18:1), and (iii) the annotation of lipid regioisomers following MS/MS annotation of the lipid derivatives obtained following the aza-Paternò–Büchi reaction (e.g., PG 16:0_18:1 ω-9). Once the platform was set up, the lipid extracts from 8 seaweed species from different seaweed families were characterized, describing over 900 different lipid species, and information on the regiochemistry of carbon–carbon double bonds uncovered unknown peculiarities of seaweeds belonging to different families. The overall analytical approach helped to fill a gap in the knowledge of the nutritional composition of seaweeds.Graphical

Designing sustainable antioxidant and anti-inflammatory ingredients from seaweeds for functional gummies

Atlantic wakame (AW) and sea lettuce (SL) are edible seaweeds commonly produced in Asia and Europe, typically consumed as fresh or dried biomass. Because of the short shelf life, developing new post-harvest treatments, such as the extraction of bioactive compounds, is essential for establishing reliable macroalgae supply chains for food applications. This study aims to develop a sustainable and functional seaweed-based food ingredient rich in bioactive compounds for functional food applications. The results indicated that ultrasound-assisted extraction using 70% ethanol for 10 min was optimal for both SL (410±23 mg of gallic acid equivalent [GAE] per kg) and AW (666±63 mg GAE/kg). Both extracts exhibited chemical antioxidant activity and inhibited the protection of human plasma against chemically induced oxidation. SL extract did not exhibit free radical scavenging activity (DPPH). Importantly, no cytotoxicity (IC50>250 µg/mL) was observed in human-derived THP-1, HUVEC, HT-29, and HepG2 cell lines, ensuring the relative safety of these extracts for potential food technology applications. AW and SL extracts (100 µg/mL) reduced intracellular reactive oxygen species generation in lipopolysaccharide (LPS)-challenged THP-1 cells by 66% and 30%, respectively, highlighting the higher antioxidant activity of AW extract. AW and SL extracts did not modulate TNF-α and IL-6 secretion to show anti-inflammatory activity. Gummies infused with AW and SL extracts had a higher total phenolic content than commercial products, but their antioxidant activity was lower. Sensory evaluation revealed that gummies containing seaweed extracts received lower scores for colour, taste, overall impression, and purchase intention than those without extracts.

The effect of adding Gracilaria on flavor and quality of low-salt fermented soy sauce

With the increasing awareness of health, there are higher expectations of customers for the unique flavor, umami, and nutritional value of soy sauce. To explore the potential application of edible seaweed in soy sauce, this study utilized high nutritional value seaweeds to ferment soy sauce and investigated the effects of the addition of Gracilaria on the physicochemical properties and flavor substances of soy sauce. The contents of amino acid nitrogen and total nitrogen in Gracilaria soy sauce were 0.8 g/100g and 1.4 g/100g, respectively, which were higher than those in traditional soy sauce. The free amino acid content of Gracilaria soy sauce (17.82 mg/g) was 1.35 times higher than that of traditional soy sauce, the organic acids content of Gracilaria soy sauce (15.78 mg/mL) was 1.12 times higher than that of traditional soy sauce. Compared with traditional soy sauce, the addition of Gracilaria promoted the accumulation of pyrazines and acids in soy sauce, which contributed to the seafood-like flavor. In general, the addition of Gracilaria to ferment soy sauce can improve the quality and give it a unique flavor. This study can provide a reference for improving the quality and flavor diversity of soy sauce by using seaweed as a fermentation substrate.

Marine Bioactives in Cancer Prevention and Treatment

The twice high incidence risk of cancer in men was the reason for over a million new cases and deaths recorded globally in 2018. The two most frequent cancer-related fatalities are lung and breast cancer. Novel therapies have been made possible by developments in immunotherapy, biology, and pharmaceutical design. Novel cancer prevention and therapy elements are being made possible by technological advancements and studies on marine natural resources. The creation of innovative anticancer medications is utilizing marine-derived natural products (MNPs). Biologically active polyketides, high molecular weight organic sugars, terpenes, bioengineered alkaloids, and marine animal peptides are some examples of these MNPs. Anticancer drugs are also developed with the help of plants, animals, invertebrates, and microbes found on land. The National Cancer Institute is exploring the potential of nutrition and food in cancer prevention despite the absence of preclinical and clinical data. Marine organisms contain bioactive compounds that have potential anticancer effects. Polyphenols, polysaccharides, and alkaloids are some of the active components found in marine species. Polyphenols, found in edible seaweeds like Palmaria palmata, can lower cancer cell division and proliferation, while polysaccharides trigger the innate immune system, causing apoptosis in pancreatic islet cancer and human leukemia cells. Alkaloids, derived from marine sources, can inhibit cancer cell development. Peptides, found in various plant species, have shown cytotoxic effects on several human cell lines, including pancreatic, breast, lung, and bladder cancers. Marine drug approval faces challenges like the possibility of a resurgence of different metabolites due to environmental conditions and limited lead compound availability.

Reactivity, Pathways, and Iodinated Disinfection Byproduct Formation during Chlorination of Iodotyrosines Derived from Edible Seaweed.

Iodine derived from edible seaweed significantly enhances the formation of iodinated disinfection byproducts (I-DBPs) during household cooking. Reactions of chlorine with monoiodotyrosine (MIT) and diiodotyrosine (DIT) derived from seaweed were investigated. Species-specific second-order rate constants (25 °C) for the reaction of hypochlorous acid with neutral and anionic MIT were calculated to be 23.87 ± 5.01 and 634.65 ± 75.70 M-1 s-1, respectively, while the corresponding rate constants for that with neutral and anionic DIT were determined to be 12.51 ± 19.67 and 199.12 ± 8.64 M-1 s-1, respectively. Increasing temperature facilitated the reaction of chlorine with MIT and DIT. Based on the identification of 59 transformation products/DBPs from iodotyrosines by HPLC/Q-Orbitrap HRMS, three dominant reaction pathways were proposed. Thermodynamic results of computational modeling using density functional theory revealed that halogen exchange reaction follows a stepwise addition-elimination pathway. Among these DBPs, 3,5-diiodo-4-hydroxy-benzaldehyde and 3,5-diiodo-4-hydroxy-benzacetonitrle exhibited high toxic risk. During chlorination of MIT and DIT, iodinated trihalomethanes and haloacetic acids became dominant species at common cooking temperature (80 °C). These results provide insight into the mechanisms of halogen exchange reaction and imply important implications for the toxic risk associated with the exposure of I-DBPs from household cooking with iodine-containing food.

Sea Vegetables: An Alternative Food Source: A Review

Seaweeds or sea vegetables are the non-traditional vegetables largely produced and consumed by China, Japan, Korea, Indonesia, Philippines, Malaysia, Vietnam and other island countries. They are rich in essential nutrients, including minerals, vitamins, amino acids etc. making them a valuable addition to a balanced diet. Moreover, they have low caloric content and are free from cholesterol, essential for weight management and heart-healthy diets. Additionally, sea vegetables contain unique bioactive compounds such as polysaccharides, polyphenols and omega-3 fatty acids, which have antioxidant, anti-inflammatory and anti-cancer properties. Globally the demand for seaweed as vegetables along with its several value-added products are increasing day by day. The cultivation of seaweed is cost effective as it does not require seeds, fertilizers, pesticides, no freshwater and arable land. Sea vegetables can serve as bio filters by absorbing excess nutrients from aquatic ecosystems, thus promoting environmental sustainability in coastal aquatic system. To combat hunger, achieve food security and protect the environment, it is crucial to create public awareness on the health benefits and nutritional value of sea vegetables. More in-depth research and developments are required to commercialize, explore the diversity of sea vegetables, develop innovative culinary applications and establishment of quality and safety standards. The present review works highlights a comprehensive overview of seaweed diversity, nutritional composition, health benefits, diverse uses, cultivation methods and potential for developing processed products for food and agricultural industry.

Extraction, phytochemicals characterization, in vivo and in vitro anti-diabetic ability of non-extractable polyphenols from Undaria pinnatifida

Undaria pinnatifida (Up) is an edible seaweed known for its abundant nutrients and active compounds. In this research, six different methods, including acid hydrolysis extraction (AHE), alkaline hydrolysis extraction (LHE), enzymatic hydrolysis extraction (EHE), as well as their combinations with ultrasonic assisted extraction (AHE-U, LHE-U, EHE-U), were applied to extract non-extractable polyphenols from Up (UNEPPs). Results revealed that LHE-U was the most effective way to extract UNEPPs, it gave the highest yield (1.26 %) and total phenolics content (29.88 μg GAE/mg E), as well as considerable antioxidant and in vitro hypoglycemic effects. HPLC-Q-TOF-MS/MS analysis revealed the identification of 36 compounds from ULNEPPs, ferulic acid, p-coumaric acid and ferulic acid 4-O-glucuronide were the major compounds. In vivo study found that ULNEPPs could reduce fasting blood glucose (FBG) level, ameliorate abnormal glucose metabolism and dyslipidemia, repair insulin resistance and pancreas islet damage in type 2 diabetes (T2D) mice. Additionally, RT-qPCR analysis revealed that ULNEPPs improved glucose metabolism through the up-regulation of gene expression levels of Pi3k, Glut4, Akt, Ampk and the down-regulation of gene expression levels of Foxo1, Pgc-1α, Gsk-3β, Glut4, and G6pc. These results evidence that has the potential as dietary ingredients for preventing and treating T2D.

Evaluation of in vitro antidiabetic and anti-microbial activity of edible red seaweed Pyropia vietnamensis

IntroductionDiabetes is one of the top ten leading causes of mortality in the world with an incidence rate of 422 million. The current study aimed to investigate the antidiabetic activity of edible red seaweed Pyropia vietnamensis.Materials and methodsCrude extract was subjected to UV–visible light spectroscopy, phytochemical screening, quantification of total tannin content, DPPH free radical scavenging, alpha amylase inhibition assay, antimicrobial activity, and glucose uptake potential by yeast cell assay.ResultsThe phytochemicals study revealed the presence of alkaloids, glycosides, phenols, lignins, saponins, and further, total tannin content was estimated to be 3.86 ± 0.00378 mg/g. The methanolic extract of Pyropia vietnamensis displayed the highest DPPH free radical scavenging activity of 35.19% at 100 µg/mL. The alpha-amylase inhibition potential of the extract showed 11.5% at 400 and 13.5% at 500 µg/mL. Glucose utilization of yeast cells treated with extract with different (5, 15, and 25 mM) glucose concentrations showed a linear increase in the glucose uptake percent. The minimum inhibitory concentration (MIC) of Pyropia vietnamensis extract against E. coli MTCC-443 and S. aureus MTCC-96 was found to be 250 mg/mL and 125 mg/mL respectively. The uptake percent was 31.7, 29.5, and 38.27% for 5, 15, and 25 mM glucose concentrations respectively, exhibiting its ability to transport glucose across the yeast cell membrane. The toxicity study resulted in a more than 60% cell survival rate in all the concentrations, proving its safety for human consumption.ConclusionThe result of the study concludes that Pyropia vietnamensis could be utilized as a functional food due to its dietary source for treating diabetic conditions naturally. Further research can be done to evaluate the potential of diabetic mouse (in vivo) conditions.

Effect of elevated CO2 and temperature on Ulva lactuca growth and biochemistry under variable nitrogen levels: predicting future conditions of edible seaweed farming through land-based cultivation system

Effect of elevated CO2 and temperature on Ulva lactuca growth and biochemistry under variable nitrogen levels: predicting future conditions of edible seaweed farming through land-based cultivation system

Dietary Porphyra tenera ameliorated dextran sodium sulfate-induced colitis in mice via modulating gut microbiota dysbiosis

Bioactive components from Porphyra tenera (PT) have been reported to confer various health benefits. The role of PT in inflammatory bowel disease (IBD) has not been fully investigated. This study aimed to explore the anti-inflammatory properties of PT on dextran sodium sulfate (DSS)-treated mice. PT supplementation attenuated the severity of colitis in DSS-treated mice, evidenced by the reduction of disease activity index (DAI), restoration of colonic histological damage and suppression of abnormal inflammatory response. Sequencing analysis indicated that intake of PT alleviated DSS-induced gut microbiota dysbiosis, accompanied by reversing the generation of short-chain fatty acids (SCFAs) and bile acids (BAs). Overall, our findings demonstrated that supplementation of PT attenuated the severity of intestinal inflammation and ameliorated gut microbiota dysbiosis in a murine colitis model, which provided a rationale for further application of edible seaweeds for preventing inflammation-related disorders in humans.

Lectin from edible seaweed Meristotheca papulosa exhibits a high digestion-resistant property

The physiological impacts of polysaccharides and lipids in seaweed on human health are becoming clearer, but the behavior of the protein components, especially lectins, after ingestion remains poorly understood. In this study, we examined the resistance of edible red algae-derived lectins to digestive enzymes. We found that a lectin extracted from Meristotheca papulosa (MPL-1), belonging to the Jacalin-related lectin family, was relatively stable when subjected to both peptic and tryptic digestion and retained its hemagglutination activity after 24 h of digestion. The activity of MPL-1 was also maintained without a large change for 24 h following exposure to enzymes such as papain, Actinase E, and proteinase K, suggesting that MPL-1 possesses a strong resistant property against proteolytic digestion. We examined the anti-proliferation activity of the MPL fraction from the algal body against HT-29, a human colon cancer-derived cell line, and found that it showed a strong inhibitory activity with a half-maximal inhibitory concentration of 4.5 μg/mL. This activity was nullified in the presence of yeast mannan, an inhibitory sugar compound of lectin, demonstrating that MPL expressed its activity through binding to the glycan moieties on HT-29. This study indicates that this proteinase-resistant lectin could play a vital role after ingestion and is expected to have an inhibitory effect against colorectal cancer.

Iodine identification in major edible seaweed Kappaphycus alvarezii and establishment of an iodine reduction method for its protein extract for utilization as a protein source

Kappaphycus alvarezii is the most widely cultivated seaweed globally. The use of the protein contained in K. alvarezii as an alternative protein source seems to be an effective countermeasure against the protein crisis. Here, we identified the iodine chemical species in K. alvarezii and developed an iodine reduction method. We used various fractionation methods and showed that almost all the iodine in the K. alvarezii alkali extract is present as an iodinated protein, and reducing the amount of iodine per protein was difficult. Subsequently, an iodine reduction method was established to cleave the covalent bonds between the protein and iodine, and we could successfully reduce the amount of iodine per protein by approximately half.

Bioaccumulation, biodistribution, and transformation of polyvinylpyrrolidone-coated silver nanoparticles in edible seaweeds

Seaweeds are recognised as a potential eco-friendly food source. However, some species have shown the capacity to bioaccumulate many substances of diverse nature, such as inorganic nanoparticles (NPs), which may have potentially harmful effects on them. Among these NPs, silver nanoparticles (AgNPs) have been used to enhance the antifungal and antibacterial properties of the final consumer products, such as textiles and food packages. Their potential release into the aquatic environment raises significant concern, increasing the probability of interaction with aquatic biota, such as macroalgae.In this work, we investigated the differences in bioaccumulation, biodistribution, and transformation of NPs as a function of seaweed species. We selected polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) as model NP since they remain colloidally stable in seawater, focusing the study only on single particles and not on aggregates. The study was conducted on two different seaweed species with high commercial interest and value as human food: the red seaweed Palmaria palmata and the green seaweed Ulva fenestrata. Single-particle inductively coupled plasma mass spectroscopy (spICP-MS) analysis showed high and similar bioaccumulation of PVP-AgNPs in both seaweeds, in the range of 109 NPs/g of seaweed. However, electron microscopy with energy-dispersive X-ray analysis demonstrated that their time-dependent distribution and transformation in the algal tissue, mainly dissolution and formation of sulfur-rich corona and/or sulfidation, highly depended on the seaweed type.These results indicate that special attention should be given to the presence and transformation of AgNPs in seaweeds intended for human consumption. Not only the dissolution degree but also the speciation of these NPs could heavily impact their bioaccessibility, bioavailability, biodistribution, and toxicity to humans after ingestion.